classic motorcycle forum

Hi,
I havn't bee on here for a while so apologies
Get the relavent BSA service sheets first of all
To get the inner gearbox (not timing) cover off You will have to strip down the clutch side and remove the clutch centre adaptor. This requires a threaded puller.
Once that is off then the complete gear cluster, minus the high speed gear will slide out once the screws are removed.
Taking the speedo drive and layshaft apart is a bit chicken and egg
Once the retaining pin is removed, then the spindle bush must be pulled up and out and then the drive spindle removed before the layshaft will release from its bearing bush.

Its been a while since I had on on the bench ? so I am trying to remember if its possible to remove the inner cover and leave the innards in place by removing the kickstart ratchet mechanism?
My method of assembly is to fit everything to the inner plate and slide the complete cluster into place.
Any excess end float in the shafts or selector drum will cause mayham!!!
Shimming has to be done very carefully in order for the sliding dogs not to get too close to the gears that are not in play or in neutral.. Having the box fixed on a bench vice with the rear cover removed is best.
The linkage pins and ratchet gearchange claws must not have any wear and it is a delicate balance to get every thing correct.. 
A friend was knocked off his plunger B31 and bent the gear lever a touch, but it must have distorted something, as it would not select third-top
I spent hours and days swopping bits about and still unsure how it finally came right.. Theres very little in the books on how to "" fix these buggers" when problems arise

https://draganfly.co.uk/product-category/bsa/sparesparts-for-bsa-a710-b3133-c101112-m202133/engine-
gaskets-gearbox/gearbox-abcm/b-m-group-1938-62-plunger-rigid/

John

Yes that's an engine by A.W. Wall - think ROC. It was rated 3 1/2 hp, so somewhere around 500cc. Lewis only used it 1909-10, as the Precision - or at least the Lewis engine built for Lewis by F.E. Baker - became available.

Glenn found the frame; I described the engine and told him if he could find one I'd give him the exhaust system. He found it and I gave it to him!

1910 was an extremely chaotic year at Lewis. They offered Wall, Stevens and Precision engines, air- or water-cooled, in either the old Chater Lea set (with the Simplex leaf-spring front suspension) or the new Chater Lea set with the leading link CL suspension fork.

Cheers

Leon

"I fitted the 0.060 thrust washers on the timing side, and a 0.023 on the output side..."

I guess this is part of the mis-matched engine thing. It would be nice if there were no shims between the face of the crank and the bearing inner. Usually this is accomplished by shimming the bearing outer in the crankcase. As it stands, your shims are pretty large and heavy, and there could be quite a "hula hoop" effect as they spin around the main shafts (or the shafts spin inside them), which could cause damage to the shafts and/or the shims. In reality, if you're not going racing, it will probably be ok. But it would worry me. Maybe check with your JAP man?

You mention there is not much end thrust when the engine is vertical: true provided the piston is square and centred. You might be amazed to see the inside of an engine that has been running with a bent con rod!

Leon

I took a 0.050 and a 0.040 thrust washers out of the engine when I stripped it, and the internals seemed ok. The engine is pretty unstressed and won't be used for racing or anything.

The thrust washers are part of the design on the engine, it's not possible to adjust the main bearing liners, they're pressed into the cases, and the thrust washers/shims allow for the end first to be adjusted. This IS a 1930's design....

But you're right that a call to the expert is in order.

I guess I should also state that I don't want to be grinding material off the crank itself; I could grind down that nut and the crank-pin shaft end to get more clearance; because I don't want to mess with the crank's balance: I've no idea how well balanced it is.... but I don't want to mess with it!

Didn't really feel like going into the workshop last night, but nevertheless I did.

Firstly I cleaned off the timing side case:


To check exactly what is hitting what I improvised some "engineers red"

(It's a red paint pen )

Gently fitted the crank and rotated it slowly a few times (only a few)


As I thought.....




I think the crank-pin nut is also slightly scrapping the slightly proud area of the casing, the ring around the bearing liner. Hmmmm.  But it's definitely hitting that screw head.
For Reference: that test was done with a 0.023 and a 0.010 thrust washer fitted (which is how it was setup when I discovered the issue).

I found a nut for helping to hold the screw in place in the vice:



Then gently and slowly took some material off the head of the screw with a file:


The (nearly) end results:


Fitted back into place:


That should be an "improvement", but I think the clearance is still going to be somewhat tight....


I then took it out again and cleaned up the slot a tad: (not very well unfortunately, but it's still functional)


I then played with thrust washers for a bit, trying to get the clearance: even with a 0.050 thickness thrust washer there was a slight scraping still happening, so I added the 0.010, and it's clearing now.  This was done with the timing side case lying on the blocks, so the full weight of the crank was pushing down on the thrust washers/bearings.  In practise, that won't happen, because the engine isn't mounted lying on it's side!   (IE, it's the "worst case scenario" for this clearance: heat not included....)

I'm aware that when the engine gets hot this clearance may reduce, but I'm hoping that by setting the clearance as large as I can, that danger will be mitigated at least somewhat. 

I'm still trying to figure out why this has become an issue when I can only assume it wasn't a problem before. I've had a look back at the photos from when the crank was rebuilt, and the ONLY nut that was removed during that process was the output side crank pin nut, nothing else was touched: so - this problem nut is the original one, and it's in exactly the same state/position as it was before.... so I'm no more enlightened as to why this nut is striking the cases as I was before. Hmmmmm.

Anyway:  I fitted the 0.060 thrust washers on the timing side, and a 0.023 on the output side..... and checked the end float:
Base:

Float:


That's not bad!!  There IS float with the thick timing side thrust washers, and I have a 0.020 washer that will bump the float up to between 0.012 and 0.015, so looking good so far.

I need to fit that 0.020 washer, check the float again, and check the piston is at least vaguely central in the crankcase mouth and the piston is central in the barrel, but dinner was calling me....

Bloody thing!