1929 J.A.P 250cc Sidevalve engine problem

[windy]

There should be a small valve that admits oil into the crankcase on my 1929 J.A.P 250cc sidevalve. Problem is there is nothing inside the valve casing. Looking at a very feint diagram I can just about see there should be a ball bearing in there, but my question is should there also be a spring?

[cardan]

Hi Windy,

This is part of the one-way oiling system that is common on JAP motors. If you need a valve here, there should be a small disk (cut from thin-but-rigid brass shim, or Coke can) that sits inside the recess in the lower fitting. Make sure it is flat with cleanly cut edges so it doesn't get stuck. If you look you'll see that the oil can always run down into the crank case with the disk in place, but when the crank case is pressurised (on the piston down stroke) the disk will lift off its seat and seal firmly on the bottom of the upper part of the fitting (which has a flat bottom). i.e. it's a flapper valve.

Do you need one? Your bike probably has a drip feed from the tank. If there is a similar one-way valve between the sight glass and the fitting on the crank case, there is no need for another. If there isn't, make a little disk for the fitting in your photo.

(By the way, make sure the rest of the oiling system has flapper valves where they are meant to be, and that no one has drilled holes between the timing chest and the crank chamber to "improve" oiling. The JAP system works well, but it has to be all in place...)

Leon

[windy]

Thanks for the reply Leon. The oil is fed from a "Best & Lloyd" oil pump, driven from the timing gear, with no sight glass, so I'm going to use a section of clear pipe to keep an eye on the oil supply in future. The disc valve idea sounds reasonable enough but i think its a ball bearing shown in the parts diagram, as far as I can see. I was just wondering if there should be a light spring above it but now guess its just gravity that does the job, with crankcase pressure lifting it on the downstroke? The pair of big disc valves between the timing case & crankcase are present.

[chaterlea25]

Hi Windy,
On some engines the brass part sitting into the crankcase has a spring under neath so as to keep it in contact with the screwed in top part , others are screwed in , care must be taken so that the two pieces sit against each other or the little disc will not stay in its seating
I have mad the discs by soldering a piece of steel shim or feeler gauge around 0.015in thick to the end of a round bar and then turning to size, some heat will then release the disc
Theres a replica B& L tell tale available here http://www.vintage-replica.cz/374.E.htm

Regards
John

[cardan]

If there is a ball and a spring in the oil feed, it is probably designed to stop the contents of the oil tank running into the sump when the bike is not in use. It will be arranged so that the oil under pressure from the oil pump lifts the ball off its seat and forces its way past, but won't get past by gravity alone. A steel ball, and in particular a steel ball and a spring, will have enormous inertia compared with the lightweight shim flapper valve, such that I doubt it would do anything in response to the fluctuations of crankcase pressure on each cycle. The fitting you show in the photos is for a disc valve which is, if you like, "normally open" (oil will run into the crankcase via the grooves, even when the engine is not running). I'd expect a ball and spring to be "normally closed", forced open only when the pump is providing oil under pressure.

However you set it up, just make sure oil goes into the motor when you're riding!

Cheers

Leon

[windy]

John,
thanks for explaining. I couldnt work out how a disc would work, and imagined it would be floating up & down & around all over the place if it was inside the valve body, but now I understand, it sits "between" the valve body & seat. The valve body you can see in the pic was fitted upside down, so caused a lot of confusion! The seat is screwed into the crankcase, hence fixed, not sprung in this instance. Thanks also for the link to the B&L tell-tale. I could do with one so will likely buy one from him when he comes to Stafford shortly.
Leon,
glad I didn't assemble it with a steel ball now.
I've pulled the engine completely to bits & thankfully caught a few other botches before they wrecked the engine. The "engineer" I bought the bike from, who "rebuilt" it less than 20 miles ago needs locking up!

[windy]

Managed to find some shim stock this morning & used a sharpened gasket punch together with a block of (very) hardwood to punch a disc out. Thanks for the advice guys. Looks like we are getting somewhere now

Next challenge is to sort the worn timing side crankpin & bush out.

[cardan]

The flapper valve looks perfect; main shaft not so much!

Leon

[windy]

Yes, not so good. Caused by the PO bolting the crank together without any regard to it running true. The crank webs were closer together at the big end than at the opposite side, causing the main bearing pins to flex up & down on each revolution. This has also knackered the timing gear, but luckily I have managed to obtain one. The opposite main bearing is made up of loose rollers, so a new set should sort that out. Oh, and he managed to put the big end roller cages together wrong too, the double cage spacing washer was not in the middle between the cages as it should have been, but between one crank face & the bearings. Crank pin nut locks were made of pieces of cut off brass screws that were hammered over. They were only screwed in about 2 threads into the crank webs. "New" piston ring gaps were about quarter inch, not 8 thou as recommended. Cam & followers badly trued up, loose fasteners virtually everywhere inside the engine, the list goes on & on. This guy gave me a business card to say he rebuilds druid girder forks for a living. Heaven help those he has worked on!

[cardan]

Disappointing, isn't it?

I note that Radco's book "The Vintage Motorcyclist's Workshop" is back in print. If you're doing work on an old bike, get a copy and read it - it's a terrific volume full of detailed information on all aspects of restoration. If you're not following Radco's advice on issues like mainshaft runout, ring gaps, piston to cylinder clearance etc., make sure you have a good argument why your ideas are better than his!

My bikes often look a bit shabby (didn't spend much time reading the sections on painting and plating) but they usually run well. It's nice to get compliments on how well a bike is running; it will only run well if careful thought and fitting is put into the restoration.

Cheers

Leon

[Rex]

Always makes me wary when someone describes themselves as an "engineer" when they're selling a bike. "Engineer" is a broad term, and while he may be a time-served skilled mechanical fitter (in the true sense of the word "fitter") he could also be someone who services dishwashers, installs software upgrades or even designs space rockets, none of which would give him any skills or insight into how an old engine needs to be put together.
Then again, the old joke about mechanics' cars is very true too...

Looks like it's coming on well though.

[wetdog]

cardan...... for me also the running is of more importance than the look , in fact i enjoy more a bike that looks like shit but goes like it also , i admite i did buy a tube of solvol in about 1976 and have just noticed the half tube left has gone quite hard , im thinking of taking it back but the shops gone .