Troubleshooting a JAP Special

[Rockburner]

The new rear-shock mount bolts turned up.

Exactly as specced:




The left side:


With the pannier-mount in place, the shank does reach through to the outside of the mounting plate - exactly as measured.



Did the nuts up loose, just to hold things together for now.


On the right side I can either spin the die down one of the bolts to make the shank the right length - or simply pack out the nut like this, with a couple of extra spacers.


This is how the pannier will sit, but it will have a secondary nut and bolt to hold it straight as well.



Should be much better, out of the way, and won't interfere with anything that moves.  :thumbup:
I'll probably use tie-clips or something similar to prevent the bag moving along the axis of the bike (currently it can do that - but it won't fall off the mounting bar, the bar is too long).  I'll get it all mounted tight and see what the best solution for that is later on.

[Rockburner]

err, not been in the shop much over the hoidays... but managed to get in last week for an afternoon of shivering.

It's been preying on my mind somewhat that the measurements I took for the crank play weren't very accurate... so I decided that I really ought to do it properly with a dial guage.  It was with this in mind that I entered the shop....


.. and pulled out the toolbag support bracket to finish off that job first.  :roll:

So - first the next hole up needed a little file so that I could get a small bolt through it inline with the hole in the frame


Top view of the assembly in situ:


Internal view: Washer and lock washer in place


Just a view of the main shock support bolt in place.


And this is the tie-clip just stopping the toolbag falling forward or backward during riding (it can't fall off)


SO - with that done.... I remembered the dial guages...

I currently have 3: an imperial one and 2 metric ones - all bought randomly from jumble shows ( why I haven't just bought a new one from wherever.com is a mystery.... it had just never occurred to me.)

The imperial one seems to move and work ok,  the Draper one seems to have a sticky movement, and the other metric one is ...well... just iffy.

So - in the best bulldog spirit of pressing forwards with the most important jobs....

I prevaricated again and started dismantling the sticky dial guage to figure out what the problem is....

Looked ok at first glance...


However..... the eyeglass reveals all...  (this thing is turning out to be really useful! )
(open the photo in Flickr and you can zoom in.)

The teeth on the main shaft are $%^&&ed. :roll:

So - instead of hurling the thing across the workshop in a fit of pique (it was tempting.... )

I calmly placed it to one side to see what was wrong with the other metric guage.

Hmm - something missing from here... I'm sure of it!


...

...


Can you see where this is going??

Can you?



I bet you can.


Yup !
FIXED IT!




In addition... the knackered guage had a mounting lug on the back, and the newly fixed one didn't... so I figured that while one lug may not be as good as two lugs, it's still better than no lugs if lugs are to be needed.... (ahem) so I decided to fit the back from the dead guage onto the fixed one.....

which has 3 equally spaced threaded holes to secure the backplate.

The backplate with the lug... has 4 .... equally spaced ... holes.


<sigh>

FINE!


Get the drill out, carefully layer the 2 backplates so the old one can be used as a template..




And bingo!

A fully functioning, belugged, metric dial guage!  (sorry, no photo.  )

I also dug out a nice bit of ally hanging bracket (or something) to use as the "stand" for the guage - I can screw it to a bolt-hole on the cases easily enough.

I just need to reassemble the crank in the cases and figure out the arrangement of the guage....


Which will probably happen this week at some point... hopefully.

in the meantime... I'd be a lying little toerag if I claimed I wasn't strongly pondering the purchase of one of these...
(or similar)

[Rockburner]

Had a fun afternoon yesterday fiddling with the flywheel (dem tings are heavy)

Parts assemble!


First assembly:
Yes - I did you a little video! 
(yes, the music was too loud... my bad!)
https://youtu.be/C0fcM7KXcNU
(I initially wanted to do a time-lapse video... but I ended up just posting it as is)

This is how the dial guage ended up being mounted - seemed to work well and enabled a consistent (mostly!) location:


It took a bit of fiddling to get the dial to zero properly (with the crank pulled all the way to the left).


Finding the initial float:
https://youtu.be/E4PKg67gMYo

Correction: the end float should be 0.012" - 0.015"  (I made the same misread last time - because it's written in the booklet as .012"  (the initial 0 is missing so I keep misreading it!)


Maths.



I initially chucked in 2 0.023" shims, one each side to see where that got me - theoretically, that should have been very nearly there....


The results:
https://youtube.com/shorts/MKNfHrS-ffc

I was also trying to get the conrod as central as possible - using the crank-case split line as the centre-line (an assumption - but I think a relatively safe one.... I hope!)

The polished crank means it's "relatively" easy to see where the conrod is
Crank pushed to left

Crank pushed to right.


I then added a 0.020 shim to the Timing side (right side) of the crank, and still had too much float (0.02xx something IIRC)

So I added a 0.010 shim to the left side as well


Too much??


Or just right?




While I pondered that...

I pulled out the compression plates that I have (which would sit under the barrel), which I was going to use as templates for the base gasket,  and luckily had the thought to try them on the cases while I had the cases together.

They're not JAP.

Well - they might be JAP.... but they're not THIS Jap! 

GAH!   

I suspect they're from one of the other bikes... the Matchless maybe? 

So - I also checked the spare head gaskets I found... and THEY'RE not right either!  I could possibly use them... because while the inner diameter of the gaskets is larger than the bore, the outer diameter is considerably smaller than the outer diameter of the depression the gasket sits in!  GAH!

I also have a box full of piston rings that I know are wrong (I think they're pre-war JAP)

So - I did a bit of tidying up...



TBH, I think the float is now acceptable, so I dry assembled the piston and barrel (no rings or gudgeon pins)


On a full 500cc engine with 15:1 compression... the piston should come right to the top of that barrel....

https://youtu.be/jHgrizea2ik

There's a fair bit of play in the small end - so I figured I could see roughly how central the conrod/piston is by gently lifting the barrel and observing the small end :


It looks ok to me!

Happy Bunny!  Didn't need to buy more shims this time around.

Next job is to do some light grinding paste action with the barrel and the cases - the faces of the cases where the barrel mounts are a little lumpy, so I'm going to use some light grinding paste just to get the barrel and crank meeting faces "flat" which will a) help the paper gasket seal better and b) maybe possibly increase the compression by a gnat's chuff?? hey - every little helps!

After that - make up the barrel gasket and the oil-chest gasket (the volume under the timing chest where the oil collects for dispersal post use), and the gasket for the fitting under the oil-chest.  I'm thinking I'll probably make up 2 or 3 of each: so I have spares for the future, and in case I have any accidents in assembly....

Then it's <gulp> time to start final assembly....

Although - I do still need to assemble the head and check the valves are sealing: using meths or paraffin this time!

I hope it gets a bit warmer soon.... at the end of every evening like this the ends of my fingers are freezing.

[Rockburner]

I'm starting to think that I really need to get in the workshop a bit more often - there's still a lot to do, and I'm definitely taking my time with things.

So - last night I went in and made gaskets. ... I know, it's soooo exciting!

Some of the parts that need gaskets, with existing old ones:


I started with the output side shaft seal plate gasket - this is a "non-standard" fitment anyway to slow down the loss of oil around the output shaft.


The outer and the fitment holes were relatively simple - but I need to break out the school-boy drawing tools for the inner circumference.


Note to self... for f*cks sake draw on the OTHER side....


But a reasonable finished product.


Next - the oil-drain chest cover.


Should be functional:


Funnily enough - the oil-collection chest gaskets can be bought, but this is an older one that's been used, and I can use it as a "master" template: it's a bit out of shape, but not enough to be a problem:




Much easier to work on the non-printed side of the paper!




With the old one that I pulled off: I'm going to leave this one as is, and not bother to trim out the internal "web" - it's not necessary.


The last gasket is the base gasket, but first I wanted to get the surfaces a tad smoother, so I dug out the fine grinding paste....




It's an improvement (I hope).


The initial circles I drew out with a compass, then tested for fit on the barrel


I then put the barrel onto the cases and marked the cut-outs for the bolts that tie the head & barrel down, then trimmed them out and checked the fit
I also trimmed out a smalle cutout on the inner of the gasket to match the slight cutouts which allow the con-rod to not-hit the cases.


I've put them in "storage" for now, (under a couple of books as well), and will very likely make up another complete set, using these as templates.


I then decided to make another fix:
The timing chain cover has another little cover over the mag-cog to allow you to adjust the timing without taking the entire cover off: you can lock the mag-shaft, then loosen the pinion nut and tweak it through a hole in the timing chain cover.
BUT - the threads on the tiny holes were tired - so I found some new set-screws with wide heads in the box of bits: figured out what thread they were M6 as it happened, ideally it would be nice to use Imperial all over, but there's other Metric threads on the bike so I'm kinda beyond caring at this point; re-cut the threads in the timing chain cover and hey presto!


I cut the set-screws down to ensure they don't interfere with the timing chain


And there'll be another paper gasket going under that cover to reduce any oil weep (the timing chain isn't lubed much, I don't think...,  so it shouldn't be an issue really).

Actually quite pleased with the evening's progress.

Like I say - I'm going to make up another complete set of gaskets and will use that 2nd set for the build, and keep the first ones (the ones made directly from the mating faces) as the "master-templates".  I may well find there's other places where a gasket might be useful, but we'll cross those bridges when we get to them.

[Rex]

Got any spare enthusiasm going spare? I could really use some this time of year...

[cardan]

Good job Rockburner - it's a reminder of how much work goes into an engine rebuild. Pleased that you found someone knowledgeable to help with the big end and flywheels. An expert can make a tricky job look easy.

I have a couple of little worries.

I fear that not fitting a valve lifter will prove to be a mistake. Even if you keep the compression well down starting without one might be a problem. I guess you'll find out!

My other concern is about the grease in the roller bearings on the mains. Grease isn't a very good lubricant on rollers, and I fear it might stop the oil getting to the bearing. It might be worth chatting with your JAP expert about it.

Should be running again soon? Good luck!

Leon

[Rockburner]

Got any spare enthusiasm going spare? I could really use some this time of year...

HAH! I wish! Those last 2-3 pages of posts represent about 7 months of real time!   
I tend to manage about 2-3 hours a week in the workshop. I keep saying to myself I'll get in more, but never quite manage to do it.

[Rockburner]

Good job Rockburner - it's a reminder of how much work goes into an engine rebuild. Pleased that you found someone knowledgeable to help with the big end and flywheels. An expert can make a tricky job look easy.

I have a couple of little worries.

I fear that not fitting a valve lifter will prove to be a mistake. Even if you keep the compression well down starting without one might be a problem. I guess you'll find out!

My other concern is about the grease in the roller bearings on the mains. Grease isn't a very good lubricant on rollers, and I fear it might stop the oil getting to the bearing. It might be worth chatting with your JAP expert about it.

Should be running again soon? Good luck!

Leon

Good points both.

The valve-lifter i removed has been broken for an unknown period, possibly years, and i was able to start the bike anyway, so I'll see how it goes. Now I'm much more familiar with the thing, refitting it is far less daunting if i decide I need it.

Yes I am aware of the dubiousness of using grease on the rollers. I'll be cleaning them off and soaking them in R40 before final fitment. Using the grease does help to keep the assembly together during the repeated assembly/disassembly process while getting the shims sorted out. Its all good.

Thank you though for pointing out those concerns, this is my first complete rebuild of anything, and the deepest I've ever gone into the bowels of any engine, so there's lots I know I don't know, and even more that I don't know I don't know.

But the list of things I know is growing, which is good!