classic motorcycle forum

Quote from: Rex on February 10, 2026, 11:26:42 AM

Out the exhaust pipe?

Hopefully as an almost-invisible blue haze. Get it wrong and it's dripping out the exhaust, and covering your boots and trousers and the back half of the bike as it spews out from every conceivable joint.

The presence of the built-in return pump makes your engine "dry sump" rather than "total loss" (or "wet  sump" as Haycraft rather misleadingly calls it in his Book of the JAP Engine). In principle the oil goes back to the oil tank after it's had a lap through the engine.

There were many JAP oiling systems, but 1932 was the first year of dry sump: first with a double-acting Pilgrim, then after with a built-in double acting JAP pump built in. I guess the racy engines were a bit weird. What year's you engine?

You'll be able to see the oil going into to the engine through the window on top of the Pilgrim pump. Make sure you understand where it goes next: as it goes into the end of the timing-side main shaft there is often a seal of some kind (e.g. a sprung brass quill) which can be missing, and then an oilway should be drilled all the way to the big end. Use your oil can to give a good squirt of oil into the main shaft - it should come out of the big end bearing. If not, double check with your JAP engine man. (I bet he checked!) The big end will die first without oil, so it pays to be certain.

Have fun!

Leon

Edit: OK, I've been back through the thread (not much of it!!!!) and found photos on p7 that show the oil layout. There's no return pump per-se? Just the oil pushed through the flappers into the small chamber underneath, with the neck at the back where the oil exits. Onto the dirt track originally, but better just dump it into a catch bottle for the road. What a waste of good oil!

Not sure of the exact year of the engine, since (afaik) no two pieces came from the same "factory" engine: it's a complelye "bitsa" scrounged and found.  But it's essentially a late 1940s / early 1950s flat-track/speedway engine in intent, but detuned (350 crank , 500 conrod, piston, barrel, etc).

It's worth remembering that the old speedway/flat-track race engines cared a lot more about getting power from the unit than worrying about the oil loss, and on shale / grasstrack it's not going to matter if you're losing a half a litre of oil per race, you fill up for the next one! My thinking is that ny modification for catching the lost oil have come from the Formula 500 car racers who were using these engines on proper race-circuits and so needed to a) reduce droppage for safety reasons, and b) reduce costs.

These photos show the oiling system I have on this bike:




Pilgrim Pump mounted to a secondary pump, mounted to the Timing chain cover.  The oil comes from the tank (the outboard-most pipe into the back of the Pilgrim), fed into the engine and the head, then is "sucked" (well - I doubt there's a pressure difference...) by that pump which is inboard of the Pilgrim from the "sump" (ie, the exit of the sludge-trap) and returned up to the oil tank.

My father, when he built this bike, was very aware of the total-loss nature of the engine as it would have been originally, but he wanted a bike he could use on the road, and on classic trackdays.  So, he spent a lot of time getting this "concept" (ie returning the lost oil back to the tank) to work.  His original idea was to have the oil drain from the "sump" down to a lower mounted tank, and then pumped up to the oil tank via a modified bicycle pump which was activated by the movement of the swingarm.

It actually worked.  Well - on bumpy roads anyway.... it turned out that modern race-tracks are too smooth and there wasn't enough movement of the swinging arm to make the pump work.

He also went through a couple of variations on the theme of multiple catch-tanks, but none were very satisfactory.

So he tried a few other ideas and eventually found this secondary pump and the engine had this fitted for... the last few years (at a guess) of it's active life. 


I do need to check the oil-flow down the crank, and look into whether or not I need that sprung quill: I've seen it on the list of JAP items from Speedway Service, but pretty sure there wasn't one fitted to this engine when I stripped it.  Something to ponder and discuss with the expert.

Well, since I'd got my head down during the week, I figured I was owed an afternoon in the shed....

I've always liked the "exploded diagram" photos you see in some of the magazines... so I had a go myself.

Unfortunately I kinda ran out of room on the bench.... so there's a few items not shown. :roll:

After I tidied everything back up again, I got on with the things I had planned:
First wash the grease off the main crank bearings:
one bowl of petrol :


Aaaand about ten minutes later...
One bowl of R30 with all the pins in.   I figure they'll be safe in there until final assembly.


I also remembered that I wanted to check the valves properly, as discussed a lot further up the thread....
First I did a bit of cleaning up on the inlet manifold while I was there :


Much better.


Collected up all the valve bits.


Inlet valve went in first


Couple of Mica washers to slow down the heat transfer to the springs. I've already done all the work checking the spring-weights


The base cup and washer... and it's time to dig out the spring clamp!


This part always terrifies me..... it's like having a loaded gun with a hair trigger sitting on a jack in the box...


Especially when you realise you forgot to put the circlip on the stem. FFS.
Anyway - managed to fineagle it on without firing the springs into my face..


I actually did have to loosen it off because the springs were all leaning one way and I had to re-center the jaw of the clamp so I could get the collets on.



Note to self... put the circlip on FIRST.


(Well - after the valve goes in the guide... natch....)


Cocked and loaded.


Had to dig around for a plug, but found one.


NOT for drinking!  (well - a last resort...)


Believe it or not... that's full.




Definitely full!


And NO DRIPS!!

I am SOOO $%^&&ing pleased with myself!  I even did a little dance!

Waste not want not...


So - that's the head sorted!  
Like I say - I am really happy that the valve seal, I spent a lot of time doing that and it's very very satisfying to see that it appears to have all gone right.


I put the head away but kept the Meths out...
The next job was cleaning up the cases.


I mainly wanted to get all the grease off the main bearing liners.
There's a feed oil that gravity feeds oil from the underside of the barrel, down to the liner...
Obviously there was grease in the feed hole.


Yeah - that got messy.... I pulled some meths into the syringe and blasted it into the top of the feed hole!


I blew air through the hole quite a few times, pretty sure it's 99% grease free now - anything left will just join the general gunkiness that is the end result of CastrolR getting hot.   I used the meths to clean both cases up as best I could, including the main joining faces.

Then I started to look more closely at some of the peripheral bits of the cases.
This is the "sludge trap" which slows down the feed of oil out to atmosphere (these engines are designed to be total loss, and piss oil out onto the track - it's a speedway engien remenber!)


As in that photo, I have spare parts to replace those in the cases - but I'm not sure how to get them out, you can't really get a hammer inside the cases to knock them out from the inside, and I didn't want to get all Conan with a screwdriver....

So, while I pondered that... I spent an hour or so checking all the screws and threads for the peripherals.
These feckers are M5.


The dreaded silicon sealant....


If you look closely.... you may notice that yes, indeed, the black set-screws  (for the sludge trap catchbox) are VERY closely aligned with the oval-headed screws for the oil-trap cover...
They actually interfere with each other!!  But it's actually not a problem because the black set-screws are the right length for the catchbox.  But it gave me pause for thought as I was cleaning everything out!

I cleaned up all the threads for the oil-trap cover as well - now there's plenty of thread to ensure the cover is held down tight.


And I found a nozzle in with one of the tubes of Blue Hylomar!  that'll make life easier!



So - all the threads are clean, I've got the Hylomar all ready, the bearings are clean and soaking in oil (mainly so there's "something" to just about keep them in the cages when I assemble the cases), I've got the gaskets I need (I tried to make up some carboard templates last week, but had limited success).


I just want to get that sludge trap sorted out before I really get going on the full assembly. I've asked a question on a popular group on FB, so hopefully I'll get a response soon!

Oh - I also found that all the little parts that hold the rockers in place in their box - the washers and bearing liners had gone fecking rusty!  I think my mistake was storing them all in sealed plastic boxes after I'd been fiddling with them repeatedly last year - a mix of trapped humid air and acidic finger grease.   So I gave them all a good brass-brushing and we'll see how they fare.  The actual bearing surfaces seem to be fine - it's the rest (eg the outer surfaces of the liners) that had surface rust on them.  my dumb mistake, but I doubt they'll be problematic.


So - progress and some mistakes, but, mostly progress!

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.

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.

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.

Mag-Platform bracket mk2:

In progress:


In place:



To be honest....  I'm not convinced.  I bent that bit of steel cold, with just a hammer and then twisted it with mole grips.  I think it's just a bit of mild and may not provide the support that I would get with the thicker stuff.

But - it'll do initially and I can have another go if I decide I want to.  At least now I have a "pattern" piece for reference when making another one.

I made this one by doing the bend first: after figuring out roughly where it should be with the bracket bolted to the cases; then I put the twist in to bring the upper hole (the mag-platform end) into alignment with the underside of the mag platform.  However - that meant that the twisted part of the bracket works against getting the bracket flat against the mag-platform.

If I try again, I'll probably start at the other end - the mag-platform end, and work out what the bend needs to be from that end.  I thinkt it could be done with a single bend, but at a funny angle across the bracket, it's not quite 45 degrees - maybe about 30 or so.

Remembered I had some loom tape yesterday, so completed the job:





I also took some remediating action concerning the battery flopping about on it's single screw....


Will help for now - but a better solution will be engineered eventually.