JAPton Special motorcycle project

The old head is slowly cleaning up. I resorted to violence last night (with the dental pick).

Old photo for comparison:


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They might not look it, but they're a lot cleaner!

Did the valves and springs in petrol, and the rest in paraffin (the only 2 solvents I had in).

Will get most of the rest of the components cleaned up as I start reassembly, once the crank is done. Off to Ipswich next weekend for that.

Progress thus far:

First, the dinosaurs came, but they got all fat and sick and died and turned into oil, then came Mercedes Benzes....

ahem.


The visit up to the JAP guru in Ipswich went very well indeed. We got on very well and it was a fun morning of fettling.

I took up a few parts to get his opinion on their worthiness and discovered a few things.
Firstly - the 2nd head I bought is badly pocketed: the valves have been sunk into the head so far (by use and grinding in) that they're actually now "outside" the original hemisphere shape of the combustion chamber. I also found out the other day that the original head has had the valve-seats replaced (I think I knew this), so it's actually in better condition than Head 2 (despite Head 2 being cleaner... ).

In addition we dicovered that the exhaust valve for Head 1 is bent. That was a puzzler - because there's no evidence of it having hit anything within the chamber (the other valve, or the piston). It's why it wasn't sealing. Luckily he had a 2nd valve that slotted right in.

We also looked at the loose inlet guide, and he replaced it from his stock. I didn't know this... but the valve guides can just be hammered in and out! :wtf: The original valve fits in the new guide perfectly, so Head 1 will be back in action once it's fully cleaned up and re-lapped in. 😁 I'll probably by some flap wheels for my Dremel and have a go at the carbon build ups in the exhaust manifold myself, and then as a final resort take it to a media blaster of some sort. (walnut or vapour probably).

We also examined the rocker box : This is the best pic I could get of the issue :


What I thought was wear caused by too much endplay in the rocker arms, is actually caused by the fact that the rocker arms are the wrong arms for the box! Well - not actually "wrong" - but they've not been fettled properly! The original forging patterns for the rocker arms make them too big for the rocker-box, and it's necessary to grind off a lot of the material. When he's doing race-engines apparantly he takes off quite a lot of the material on the rocker arms, including drilling lightening holes and a hole down the ball-end! (sounds painful!). So - I'm going to take off the material necessary from the rocker arms to ensure that there is clearance for the oil-gallery (shelf), and get that oil-shelf rebuilt up - that should ensure that the rocker-bearings get plenty of oil in the future. I'm hoping that I'll be able to do that to a reasonable quality using hand-tools... we'll see.

He also explained a good trick for checking the valve-spring weights, which I'll take photos of as I do it.

He checked the piston - it's fine (needs a clean), and the cam-shaft - which is a "standard", not a race item (which is fine), and also explained a few tricks for getting that aligned correctly should it need it. All stuff I'll be checking when I reassemble it.

Then we got onto the crank (and I remembered I had a camera.... )
Separating the big end shaft from the flywheel



😁



Big end rollers - all looked ok


The big end cage is just ally - but it looked ok.


Inner faces:


At this point there was a slight bit of confusion due to the distinct lack of balancing holes having been drilled in the inner faces, until I remembered it's a 350 crank (not a 500). 😁 Obviously new cage and rollers were fitted.


Pressing the tapered big-end shaft back into the flywheel.


With some minor adjustments to get the outer diameter faces parallel :
(I now want a brass hammer!)



Things are much easier when you have the right kit....


More minor adjustments to the get the shafts aligned :


This was very much an iterative process: take a measurement, squeeze the wheels, take a measurement, squeeze again... etc. etc


The for the first few checks the nut wasn't even done up as tight as it could be ... just f-ing tight. After getting it pretty damned close, he did the nut up even tighter (using a 4-foot breaker bar and a lot of bodyweight....) then spent another half-hour getting it just right: toed IN 3/4 of a thousandth of an inch on one side, and about 1 thou on the other side. Apparently under heavy load the crank can toe "out" and pinch the con-rod, so he sets them up toed in slightly.

At the end of the session he declared that it was a "good set of wheels". Which I'm very happy about! They should now be good for quite a while, and with the use I'm expecting from the bike (pottering about locally annoying the purists 😁) they should outlast me.

As we were tidying up and nattering (another half hour at least... 😁 ) he realised that I didn't have a mag-platform steady bracket: it should look like this :


And this is how it's mounted : to the underside of the mag-platform, and to the crankcases.


The problem this fixes is engine vibration cracking the mag-platform supporting structure. So, while I have no idea why the engine didn't have one, it looks like a good idea to have one fitted so I'll try to either source one (I really should have asked him about that - so I probably will), or make one up. It needs to be good strong steel. (or whatever that fancy bronze-looking one is).

I now have all the parts ready, but still a lot of cleaning to do, and a few other optimisation jobs (eg lapping in the timing cogs to their shafts, and even lapping in the head to the barrel!).

I was reminded on Saturday of the existence of flap wheels....

So I ordered a couple up for the Dremel and attacked the carbon in Head 1's exhaust manifold


Most of it was accessed pretty easily, and came off readily:
However - you can see the parts that the flap wheel wasn't getting to.


So I dug out some crap brass-brush accessories I bought a while ago for the Dremel - they're one-use only things (because the brass bristles come loose very easily), but they certainly worked:



I eventually gave in and started scratching away at the difficult to get to bits with a dental pick - you can see the scratches in the carbon here:


Still got a fair bit to have a go at, but the worst is done. The main issue is trying to see what the f*ck I'm doing down there! 😁

Oh yeah - I was also slowed down a bit by the Dremel extension constantly falling apart - either the central cable fell out of the driven spindle at the far end, or the outer rubber casing started melting and the fitting where the extension is screwed to the motor body fell off the end of the cable!

Bit of progress tonight.

I got fed up of picking away at the carbon deposits with a dental pick (it worked, but t's bloody slow), so I thought fυck it, and banged the valve guide out so I had unhindered access. And I could clean up the valve guide itself more easily. Having seen it done, and knowing that it's literally a hammer job, made me far more confident to do it. 😁

Valve guide in improvised "gentle" vice (I really need to make up some ally / wood chuck covers for the big vice.


Much improved exhaust manifold!


I'm very aware that "polishing" the manifolds isn't going to gain me much, the engine is such low compression any gains are going to be minimal, but I wanted to do a "good job" on Dad's bike, and be proud of the end result (if I ever get there!), knowing that I did everything I could.

When I re-inserted the guide (it went in pretty easily, much as I had seen happen on Saturday), the outer end had been slightly peened closed (it happens) and I needed to ream out the guide. Luckily, I discovered that the 1 reamer I picked up from Dad's workshop was the right 11/32" size (funny that... :roll: ). Unfortunately it's a tapered shank, so I had to bodge it a bit and rotate it by hand using mole grips... :roll: But - it worked a treat and the valve is a nice snug fit in the guide. 😀

I also polished up the valves (no photos, sorry), they're lovely now. 😁

I then turned my attention to the valve springs. I wanted to check they were all still serviceable. The JAP guru I saw on Saturday had a lovely, expensive, american made tool for this - but he also described a manner of doing this using a drill press and a set of scales. So, I'd bought myself a set of postal scales that are up to the job: the desired spring weight is 145lb so a cheap set of kitchen scales ain't gonna cut it.

Unfortunately using it in the drill press didn't really work out, so I improvised...


😁

Might not be absolutely perfect to the micro-ounce.. but close enough for comparing the 4 different sets of valves that have against each other (at least).

I measured up all the springs I have - using a micrometer set to the correct length: 1.375"
The calculation is :
Desired spring length (compressed) : 1 5/16", Desired Spring weight at that length : 140-145 lb.

So - the cup and the plate within the cup that the springs sit in are 1/32" thickness each (where the springs bear) : added together that's 2/32" = 1/16"

So - add the cup & plate to the desired spring length and you get 1 6/16", or 1 3/8" = 1.375" (which is nice and easy to set on the micrometer, then lock off).

So - compress the springs, in the cups (with plates at each end), and measuring from the top of the outer spring (ignoring the top plate) to the flat sheet the cup is resting on. (In the head, you measure from the top surface of the head to the top of the outer spring, so this is the same measurement).

Results: Weight measured at spring length of 1 3/8" (inc cup & plate)
Head 1 inlet : 129 lb
Head 1 exhaust : 129 lb

Head 2 inlet : 151 lb
Head 2 exhaust: 145 lb.

So - the original springs are knackered. booo! 🙁
However - we have some nice springy springs from the "new" head. (albeit maybe a little over-enthusastic...)

I started mixing and matching to get roughly the right spring weight, but so far have only tried one combo:
Head 2 inlet outer + Head 1 inlet inner : 149 lb.

I'm going to play about with mixing the springs and get 2 pairs as close to 140/145 lb as I can. I think the measurement system is close "enough" for this. I was told on Saturday that if the spring weights are over 155 or so then they're too strong and they'll cause undue wear to the head. Given that head 2 is badly pocketed already I'm not wanting to take chances. Although Head 1 does had replacement valve-seats, so it's in a better condition.


Oh yeah - I also put the rocker arms and their accompanying accessories through the ultrasonic. Unfortunately I think I may have lost one of the frigging rollers though GAH! (mind you - I know I have a couple of spares because there were one too many in 2 of the assemblies!) Going to have to be a lot more careful with those little fuckers.

Cleaned up the carbon in the barrel and gave it a hone. (Hoping I haven't over-done it tbh...)



I used a honing tool I bought at Beaulieu, and 3-in-1 oil (after doing a bit of research on cutting fluid/honing oil - from what I found it's basically just light oil).

I also had a god at the piston crown and it's now nice and shiney. (pics to follow)

Managed some time in the workshop yesterday.

Re-checked the valve springs.


Picked the two pairs that seemed to give the right spring weights and threw the into the ultrasonic.

Here's the shiny piston:


Next step is to get the valves lapped, so I prepped the seats with a Sharpie


Loaded the valves..


And did the Twist again!


After a coarse grinding...


Then cleaned off the coarse paste, and prepped the valves..


After a fine grinding.



Next job ideally would be to lap in the head to the barrel, to ensure the mating surfaces where the copper head gasket sits mate really well, but there's a complication I need to discuss with my guy.
Where the head gasket sits is in a depression in the barrel, and the head has a matching "protrusion", and where the studs run is in the"outer ring". I'm not sure if the faces on the "outer rings" are supposed to meet or not.
Problem is that if the gasket is not in place, the "inner ring" faces don't meet when you sit the head on the barrel.
I'm not sure if I need to get some material machined off the top surface of the barrel or not.

Someone pointed out that the exhaust side wasn't quite as good as it could be... so I had another go.



I think that should be usable now.

There was a hiatus at this point.... summer, and other things just took over, but in October... I got back into the workshop.

Decided to actually get into the workshop yesterday! (other things have been happening, or putting me off), and figured I'd have a tinker with the timing chest because I was advised to check the cam-wheel/cam-follower end play before I assembled the crank.

Firstly it took we a while to find the studs, then I realised that none of the threads were very clean, so gave them a good brass-brushing.


But even then it seemed that none of the studs would cleanly go into the case, and some of the nuts refused to go down the studs easily. So I ran taps and dies over everything (took me at least 20 minutes to actually figure out the thread form and find the right taps & dies, which I DID have amazingly: turns out it they're 1/4x26tpi BSF).



Eventually I managed to get everything spun down and tight.... then realised that one of the allen head cap bolts that are used inside the timing chain case was too long for it's hole! I can only imagine that Dad never noticed this bolt was the wrong length (nothing surprises me anymore...) so I cut them both down by about 5-6mm (well - the thickness of a nut) : I did both of them so I didn't have to faff with picking up the "correct" bolt for the shorter hole each bloody time.



So - eventually I got the case to tighten down on the timing chest.... and the camshaft is jammed.

:wtf:

The Cam-followers are rattling around on their shaft as well - there's at least a mm of movement, if not more.

:wtf:

But it's the camshaft being jammed that is confusing the hell out of me. The bushes that it sits in are open ended so it's not like the saft is running up against the end of a closed hole.

The timing chest case DID have a paper gasket fitted when I stripped it down.... so I'm currently thinking that "maybe" the thickness of the paper gasket is what is providing the end-play gap offset for the cam-shaft itself.

Photos from the strip-down: you can see the paper gasket clearly.



So - the next job, I guess, is to make up a new gasket and see if that frees off the camshaft, and look for a proper shim for the cam-followers. I did find a ~1.5mm thick washer that was exactly the right internal diamater (1/2") to fit the cam-follower shaft, but the cam-followers did get "tight" when fitted - so again - if the paper gasket provides the offset.... this might work...



Oh yeah - also - over the summer I got some repairs done on the rocker-box parts:


The oil-galleries need to be machined back down to approx 3mm high and a similar thickness.
See here :


TBH, I'm probably going to do this by just fitting a dremel-esque grinding tool into the piller drill and using it as an ersatz "single-axis machine-tool" and gently take the aluminium off flake by flake...

In addition the rocker arms themselves will be ground down to be narrower (and lighter), as previously mentioned.

Another afternoon in the workshop, step forwards, step backwards.

(Actually, this was a few days ago)
Stripped down the Concentric I bought at Ardingley Classic Jumble, it's not a Premier (which has a removable Pilot Jet, where the original Concentric has a fixed size bushing, and drainable float-bowl).

It's "tired", which I expected, but all there and will make a reasonable back up if the Monoblock proves to be too much of a pain in the arse.
If I decide to try it, I'll probably invest in some updated components, gaskets, etc, and will give it a proper bzzzzzzzzzzzzzzzzzzzzzzzzzt.
The jets (at least) looks identical to the ones for the Monobloc, of which I have found quite a few in Dad's old bits so I can experiment with the main jetting at least (which is only really effective at full-bore.... 😉 )

Yesterday I had a go at making the gasket for the Timing Chest

Simple enough: the ball end of the hammer sheers the paper gasket on the hard edge of the facing with only gentle taps. These faces weren't really designed to have a gasket. Remember this is a race-engine designed for shale and grass-tracking with a total-loss oil system... weeping cases were a feature. 😁 Not great for the road or proper tracks though, so gasket making is something I feel I'm going to get lots of practise at.

Assembled up the cam-shaft and cam-followers again and its.... "better". the cam followers aren't sticking, but there's still resistance to movement from the cam-shaft itself. Stripped it down and smeared some R40 onto the cam-shaft and bushes and reassembled it
Liquid gold.....


That was an improvement, but still some stiction. So I stripped it again and smeared a lot more oil onto the camshaft, reassembled and just as I wsa tightening up the very last nut on it's stud.... fυck. I felt the thread go. Tried the camsaft rotation while it was all assembled and it's a tad better, but I still think it's a little tight, so will order up some 0.8mm paper (the gasket paper I had was 0.4mm) and see if that makes the difference.

In the meantime... stripped it all down again carefully... and fucksticks.


"Luckily" it's the hole at 5-o-clock on the face, which means it's got plenty of wall, and it's a blind hole (so no chance of crap falling out the other end later).
Hit the TracyTools website and found a 1/4" BSF thread repair kit which will hopefully turn up next week (grabbed some Imperial sized drill bits too, seeing as I don't have any at all, the sort of thing I'm sure to need at some point). Also ordered some more gasket paper.

Hey ho, not really that much of a surprise, but still a tad irritating.

For someone with the same issues as Arthur Dent, I do seem to spend a lot of Thursdays in the workshop....

Decided yesterday to stop faffing and get on with some stuff.

First, I cleaned up the drive-side crank case where the main crank bearing liner was removed:
Before.


After a few minutes with a brass brush and a wipe down


I rigged up the hot-air blower in an articulated grabber (a digital tablet holder in fact), and took a preparatory reading


After only a few minutes I turned it over to get a good spread of heat:


Then I popped inside and retrieved the new liner from the freezer, where it had been hibernating for a few months....
That's the OLD bearing liner in the background of the photos.
When I got back, the temperature was even higher than this....


The inside was a little cooler after I took the heat off:


The new liner literally fell straight in, I was so surprised I didn't even remember to give it a tap, it didn't need it.
The little locating screw went straight in too.



Light at the end of the tunnel!

This is the "feed" for oil to the main crank bearing....

While it cooled off, I pondered what to do next..... then decided to go for it and dug out the new bearing cages and pins.
oh, and the grease.... LOTS of grease!

To be honest, I think I used more grease just on these bearings in ten minutes than I've used in any single year of working on bikes....

For some reason the original size roller pins aren't made any more so the accepted practise is to use 2 pins for each slot in the cage, and alternate the positioning - as you can see in the photo.

Almost as soon as I'd taken that pic and was pondering on the pins: I realised: hang on: the old pins I took off are the OLD ones! I actually have the proper old full-length bearing pins... a complete set! But, given that I have no idea just HOW old they are, I decided to stick with the fresh ones.

So - the cases went together relatively easily for the dry-fitting, to see what the crank end-float is:
Crank pushed fully to the left:


Crank pushed fully to the right:


I measured the difference using a micrometer tail and it appears to be a movement of about 0.065" - I measured a few times, obvously, and I think the extremes were 0.078" down to 0.050" - so the consensus is about 0.065.
I checked what I'd written down earlier and read "crank end float : 0.12" - 0.15" ".

Hang on.... (I thought).

How can my end float be LESS than the desired?? Did the Liner not go in properly?? Have I got to take the liner out again?? fucksticks!!

So - I ended up having a quick call with the Guru, and while I was talking to him I took another look at the book....

which read:

Crank End Float : 0.012" - 0.015".

GAAAAH!!!! what a muppet!!! I apologised profusely to the Guru for wasting his time, he was very nice about it and we had a nice chat about things anyway, and I got on with it whilst kicking myself!!

In my defense - I'm a metric kid, I've no concept of what thousands of an inch "look" like!

I agreed with the Guru that all the crank needs is some gentle shimming (phnar) and dug out the collection of shims I've got : some new, (iirc supplied by the Guru) and some from the original build.
0.050, 0.040, 0.023(*2), 0.020, 0.010.
So - with any luck - the 0.023 pairing should be exactly what I need! 😁

Required thickness of shims: 0.065" - 0.015" = 0.05".
Desired shim width if using 2 shims : 0.05" / 2 = 0.025"

I can also potentially use the 0.010 and 0.020 to get it a bit tighter if required. but I'll have an afternoon of tinkering with that no doubt!.

I'm probably going to reassemble the cases again, dry, and double check that end-float, before deciding fully, but the crank looked pretty central so that should do the job.

This whole job was made MASSIVELY easier because I found a pair of legs for the engine last time I was in Dad's workshop:


While I as pondering things I also noticed that the cases have another set of numbers on the rear faces :


I have no idea what these would be (they're not the engine numbers, those are on the front, on the rhs), and I'm tickled somewhat that they match, given that the cases are from totally different sources!

After I'd dissassembled the crank again to put it out of the way, I figured I'd make a start on the rocker box...
Measuring up the excess that needs to come off...

Answer: a lot. These little shelves are supposed to be about 3mm high.....

Setting up the ersatz "single-axis-milling-machine" (dremel grindstone in the pillar drill!)


I used the grind stone first just to test the concept, and it worked well.
So I dug out a pot of cutting wheels. 😁



I should state that there was a good long session of faffing with a bubble level to quadruple check that the everything was as flat as possible (the drill stand, the drill plate, the clamp, the workpiece, etc etc etc)

The main faff with it is replacing the cutting wheels every few minutes, but the rod that holds the wheel is chamfered about half-way down, so it's actually very easy to put it back into the drill in exactly the same place each time: with the chamfer butted up against the outer face of the drill-clamp jaws.

I got the first shelf (the exhaust side as it happens) cut down somewhat roughly and put the rocker arm together so I could check it against the shelf. There was still a of interference, so I decided to have a go at the rocker arm as well :


This was filing down the sides of the arm, to help it clear the oil-gallery/shelf. I also took it over to the grinder and shaved off quite a bit of the metal from around the bolthole where the ball-fitting is fitted.

I'll take more photos of the rocker arm next time I'm in there. Still a lot to do, but some good progress made I think.

Got into the workshop on Friday evening....

Made some progress on the Rocker box: I figured grinding down the inlet rocker arm wouldn't take too long, and it didn't, (well, not that much!)

Inlet on left, unmodified. Exhaust on right, modified.


What need to come off mostly, is the material on the "underside" (as seen above) so that the rocker arm clears the little oil-galleries.

Closer pic beforehand


Working the underside of the arm with files. I did the material around the "head", where the screw thread is, on the grinder, then tidied up with files.


Afterwards:

I think I probably need to take a bit more off in that inner curve near the shaft, but that will depend a lot on how the clearance looks relative to the oil-gallery once that is cut-down.


This is all "rough-work" just to get the required clearances. The rocker arms will be flap-wheeled smooth and polished before re-assembly. I'm only modifiying the push-rod end. The other half that pushes down on the valve stem doesn't need any work: I'm only going for "usable" rather than "light as possible for racing".

Update from Tuesday:

Got a lot more done on the rocker box.

Working on the inlet side oil-gallery


Assembled the rocker arm bearing assemblies (which is a right faff) to check the clearances.


This is the rocker arms pushed as fair "in" as possible - which is the "worst-case scenario", I now have clearance here (just!)



I lost count of how many times I assembled, checked, stripped, filed/ground, cleaned off, assembled, checked, swore, stripped.......

But eventually ended up with a satisfactory clearance.

I was going for a "not-touching" clearance if the rocker arms ever closed up to the galleries, but when you assemble the box, the end-float is initially set by the pressue from the "lumps" on the inside of the cover. You set up the box with the bearing liner on the push-rod side as far "out" of the box as possible, and then do up the valve-side of the box tight, but leave the push-rod side screws slightly loose, so the rocker-arm bearing liner can be pushed in as the cover is screwed down, and that sets the "end-float" of the rocker arm. The photos below show roughly what clearance you get now.



Should be good! 😁

You can also just make out that I chamfered off the outer edges of the oil-galleries to give a bit more clearance. (you can see the chamfer grow through the photos 😁 )


And finally, gave the little buggers a polishing:


The other ends (the valve ends) now look a little 2nd hand.. 😁 So I "might" give them a gently polish if I can be arsed.

I may also borrow the kitchen scales to see how different they weigh, but I'm not sure it'll be much of an issue.

Managed to fix the stripped thread in the timing chest last night.

I've done this fix a few times now and it's normally relatively simple:

Drill out the hole - I took it slowly, the cases are (iirc) magnesium alloy, so they're not hard to work (and not ferrous...)


Tap the hole



Wind the insert in: Instructions say to use a light downward pressure.


Then ding the end of the insert off, invert the workpiece and the debris all falls out: simples!


Tested a stud in it... won't go in. eh?

Look closely:


f******* c*********!

The damned insert jumped the threads.

This is one of the other holes - you can see the threads clearly



Here's the "fixed" thread : you can clearly see the "threads" are twice the pitch



So - sat back, started searching t'internet for "how to remove a thread repair", and found a lot of bollox about other types of thread inserts and repairs - but then finally came across this photo :


And I thought: Hey, I've GOT a tool like that somewhere!

Yup - dug it out and presto!



Came out easy. 😁

The tapped threads were still useable.


Wound in a new insert (there were 20 in the box!) this time with no downward pressure at all, just gently rotated the tool, and it wound in easily and properly. 😀


After tidying up all the swarf, which took a while, (I must sort out that air-compressor), I started gathering the bits for making a start on the new gasket, but realised I was running out of time for the evening so packed away again.

I also discovered that the oil-box cover (the volume under the timing chest), screws are also 1/4 BSF, so if any of them go, I know I've got repair inserts. 😀

And, we're caught up. 😀

I'll keep this thread up-to-date as I go now. 😀

Good read, what a labour of love!
Cereal packet and milk carton gaskets I have come across before!

Interesting idea to use the pillar drill as a milling machine. I guess it will work ok so long as not too much lateral pressure is put on the quill bearings.

I bet you were cursing that helicoil!

Oh - there's a lot of swearing going on....

Made up the new Timing chest gasket last night.

Started out with locating the bolt holes


Punched them using a 6mm punch (closest thing to 1/4")


I hammered the edges round for about 20 minutes, and got the inner shape punched out, then tidied up the outside with scissors.
This is why kids get taught to make crafts....


Perfect fit.


The active components installed


All perfect! The camshaft rotates freely and there's a little bit of play on the cam-followers, but not enough to worry about.


I'm still pondering on getting some cap-head bolts to use instead of the studs and nuts. Dad did have that on one of the earlier incarnations of the bike, but I've no idea why it's back to studs and nuts.


So - here's another mystery. I dissassembled the timing chest again because there's still a lot to do before final assembly, and while I was doing that, a washer dropped out of nowhere into the chest.

w.t.a.f. ??

Where did that come from?

Cue about 20 minutes of utter bafflement and poking and prodding. The workbench was utterly clear before I started, and this washer definitely "fell" into the timing chest - I saw it and heard it happen!

It's NOT one of the washers from the outer casing - there's 4 of them and besides the fact that I count them all on, and count them all off again each time I assemble and dissassembly the thing: it's not the same diameter. It's 1/4" alright, but it has a slightly smaller outer diameter.

EVENTUALLY I worked out that it had come from the socket cast into the outer casing which the cam-follower-shaft pushes into.

In fact... there's 2 of them in there.


I can only surmise that they were "stuck" in the by a little bit of oil that was still in there, but still baffled as to "WHY" they are there. The cam-follower-shaft is pressed into the main cases, it's going nowhere fast (or at all!). I reassembled the chest with the washers removed to see if they were having any effect on the gapping: none whatsoever, then reassembled it again with them in place: no difference that I could see to anything at all.

I am confuzzled.

Given that they were there to begin with: I'll likely replace them on final assembly... maybe they stop vibration or something??

So. I stopped thinking about that, it was giving me a headache....

And I looked at my stock of old bits of metal, and decided to make up a mag-platform bracket.

I found a length of steel that looked about right - I think it was originally part of a foot pump...

Faced it up to the cases a few times and realised it just need a straighten and a twist.


5 minutes of heat (gas-can-torch) and some judicious heaving and belting with a hammer....


Checking the fit with a stand-in bit of engine plate


Of course I've made it so that it's bolting to the WRONG engine bolt.... the one I was shown by the Guru actually bolts to the smaller lug you can see on the photos. D'oh! BUT - it should do the job, and may even be a little easier to fit and means I won't need to compromise the engine plates (any further).

Obviously it'll be tidied up and (probably) polished once it's been proven.

Next, I turned to finding a plug for the valve-lifter-cable-hole. I'm not going to bother with the valve-lifter, at least to start with.
It may become necessary later, so I'm not throwing it away, I'd need to get the exhaust cam-follower modified again by someone with a proper machine shop.
However - all last year I managed to turn the bike over without the valve-lifter working (I always thought was as innefective as hell) so, despite a dodgy right knee, I'm hoping I'll be ok.

Rummaging through all the stuff I've got, I eventually found something that matched the threads in the casing:


No idea what this stud was from originally, but it was in the "odds and sods" box and the only person who might know isn't with us ( 🙁 ).

it's 7/16" x 26tpi.... which makes it a British Standard Cycle thread. (anybody got Bingo yet?)

It's tempting to look for a bolt in that spec... but tbh, I'm going to just cut the stud down, saw a slot in one end to make it a flat-head-screwed grub screw and be done with it by using a lot of loctite. 😁 TBH, the threads at the bottom of the hole are knackered, so the stud only goes in about 3/4 of the depth, so it does "go tight" by itself. The loctite will be to guarantee permanance. (obviously I'll be using blue.)

I'm also going to redo the plug in the top of the main cases that is over the cam-follower shaft: the plug that's in there is loose and is only being held in place by silicon sealant.....

Love this thread. It reminds me of the ... fun ... I had getting my 914 drivable again, repairing the damage from previous owners.

The Cycle taps and dies turned up yesterday..... 😁 (I ordered a set of 5 of each, 26 TPI : 1/4", 5/16", 3/8" 7/16", 1/2" as a loose set, far far cheaper than ending up having to buy them separately).

I first cut the end off the stud that I had found, tidied it up a bit and span the 7/16 Die down it to clean the threads. Then cut a nice deep slot in the top.

It fits perfectly.


Because the thread in the case doesn't go full depth, the plug does go tight.


Internal view.


Hmmmm decisions decisions.....


In the end I went with the 248, and slathered it all over. Should keep it place!

Buoyed by that success, I turned to the magnesium engine case:

First I made up a sacrificial wooden block to stop the drill plunging into the cam-follower shaft:


hmm - that ain't gonna fly: 🙁


So it got mounted in the vice.



Drilled the hole using a very specific imperial size (which I've now forgotten, albeit it is written down in the notes in the workshop) after about 20 minutes trying to find out what the correct tapping drill size should be for a 7/16" cycle thread.
My Zeus book is a Metric edition, so while it does have "some" Imperial information (ok, a lot), it's not comprehensive. And the tables in this book https://www.sunbeamland.com/wordpre...019/04/The-Vintage-Motorcyclists-Workshop.pdf which I am using quite a lot, have a gaping hole in the Cycle tapping drill sizes table. (see page 8) 🙁

I initially found information that suggested 13/32" but then found something else that suggested the next size down (XX/64 iirc) was suitable, and even that was a conversion from a metric measurement : ie the given measurement was a metric one, and I had to figure out the closest imperial drill.

So - drilled the hole, slowly and gently and when I hit the wood, it protected the shaft beneath adequately.

I re-oriented the cases for tapping the hole and remembered why I hate doing jobs like this:


It looks a lot worse than it actually is....
TBH I think the hole was a little narrow and maybe I could have used the larger drill size and the tapping would have been easier - but then I am not sure if the thread would be actually deep enough (ie the peaks of the threadform could have been flattened if I'd used a larger drill bit).

Next time I buy taps I'm going to try to buy the drill-bit from the same supplier and order over the phone to make sure I get exactly the right bits.

So - anyway, this hole isn't used for anything, it just needs plugging so a slightly off-axis thread isn't going to stop that.

I moved to plug.

Because I had a stud to cut for this, I screwed the stud in all the way until it ran out of thread and started to go tight in the hole. Then marked the untheaded part that was sticking out, and the excess that was protruding into the timing chest, and cut the plug out. Ran the Die down the threads to tidy them and cut the slot in the top:


I seemed to have cut the plug a little shorter than I intended:


But it descends to the right depth: Because it was cut from a stud, the plug threads don't go full length of the plug - so it can be done up "tight". (Given that the head of the plug is below the level of the casing outer this would indicate that the threads in the hole aren't 100% at the top of the hole - probably due to my cack-handed tapping 🙁 But - it's a plug, it's tight, it's good enough and a learning experience for the next time).


Fitted and loctitied, after cleaning the cases out with (iirc) carb-cleaner and a lot of blue paper.



By that time I was reasonably happy with the evening's work and headed in for chicken kiev and chips. 😀

Next job is (I think) either to re-assemble the head: I'm pondering whether to have another go at grinding the valves in but I had a look at them last night and I think they're ok; or to get the crank shimmed up and then assemble the crankcases together.

I may have to look for a taller pillar drill so that I can get large objects under it properly: if I'd had the tap in the pillar drill to begin with, that hole in the engine cases would have been tapped much straighter. My drill was a random find at an impromptu garage clearance and is a hobby-ist wood drill really.

I'd been dong some general tinkering the last couple of evenings, it's frigging cold out there so anything that requires proper thought is being put to one side.

I was going to reassemble the head, and made a start: I'm only going to put a couple of mica washers on each spring assembly because the spring weights are good:


But then I discovered that the valve-stem circlip I put on looked very tired, so I thought, bugger it - should replace them, and tidied the head away again for later.

Aside: This morning I discovered I've already bought 4 valve-stem circlips.... D'oh! (need to find them!)

I've been looking at the engine cases trying to figure out the best way to get the upper-surface as flat as possible (ie where the cylinder sits), and realised that the two small engine case bolts that are the first two that get used, and which hold the cases together while the engine is mounted etc really should be proper shoulder bolts, and I've got 2 set-screws. So I'be been trawling the net for a 1/4" BSC bolt with a long shank (7/8"). See my other thread for details : https://revtothelimit.co.uk/viewtopic.php?t=11380 .

So - while I was in the workshop last night I had a good furtle through my collection of Imperial bolts from random sources..... and lookee here!

"Bolt" ( aka "Partially-threaded-Bolt") on left, "Set-Screw" on right.

No idea where this came from... but I have a feeling it may actually be the exact bolt that Speedway Service sell!


Knowing my Dad, he probably didn't fit this because it's actually too long, and would look odd. It's longer, to allow the Magneto Platform Support Bracket to sit on it!

Win!

So - I spent the rest of the evening cleaning up the engine studs:


And then, because the Mag-Platform bracket was on my mind and something was feeling off.... I bolted up the cases (empty) and fitted them into the bike to check a few things :

This is how I was initially envisaging the Mag-Bracket sitting :


But... there's an issue:
The engine stud isn't long enough.


I'm going to have to rethink that Mag-platform bracket. Even though it will be a pain making sure it clears the engine plates - I think I'm going to have to use the smaller bolt as per the usual practise, so I need to remake the bracket. With any luck I can use the existing piece of metal, but if not, I do have more of that stuff, which is quite handy.

This is the rider's view when in the usual riding position :

The cylinder axis is directly in-line with your head! 😁

Incidentally: You can see the longer 1/4" engine bolt in that photo.

While I was looking at less-fundamental things I also tinkered with the "saddle-bag" fitting that I have never been really happy with: it's a cruiser-style "yoke-bag" that uses two thick leather straps and I had it hanging by the side of the saddle, banging against the shock:


I was never really happy with that arrangements, so spent some time trying to figure out a way to improve it, and found a length of Dural in the box of metal bits that Dad had drilled a large number of holes in: no idea what it was for - maybe an early attempt at a brake-tension-arm or something, but it's absolutely ideal for mounting this bag onto the bike. I'll do more photos when I do more on it, but I spent some happy moments on the grinder tidying it up somewhat for use.

So - as part of that I looked into where it would be mounted, and discovered something that made me both laugh and curse.

The bike has always been "bangy" at the rear end when riding. It crashes about and is noisy, not just from the engine. I now know why....


The shock uppers have at least 1/2" of movement side-to-side!! :wtf:

I need to look into what a regular Featherbed frame setup uses here - but at the very least I need a couple of 1/4" spacers to hold the shocks in place properly! I also think that the bolts should again have longer shanks, so we'll see what can be found, or bought to bring these shock support mounts up to scratch.

fu**** ell....