classic motorcycle forum

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.

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.

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 $%^&& 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 $%^&&ers.