classic motorcycle forum

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/wordpress/wp-content/uploads/2019/04/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

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.

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.

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".

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??  $%^&&sticks!!

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.

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.