During my search to hunt down a big oil leak onto my rear tire (1960 BSA B33) I found my gear box sprocket to be quite worn (previous dummy replaced the chain and rear sprocket but not the front one!). As I am preparing to order a new one I have the following sprocket combination: Engine 20 tooth, Gear box 16 tooth, Rear wheel 42 tooth. The owners manual says the stock set up for a B33 is: Engine 19 tooth, Gear box 19 tooth, Rear wheel 42 tooth. Both the present engine (20 tooth) and rear sprocket (42 tooth) are in fine condition. Is a 20 tooth engine - 16 tooth gear the same as a 19 tooth engine and a 19 tooth gear combination? Is there some sort of formula what one tooth added to the engine sprocket would equal in the subtraction of gear box sprocket teeth (to keep things the same)? My intuition tells me that I should at least go with a 17 tooth replacement (18 or 19?)on the gear box sprocket. Certainly don't want the bike to be geared to go slower than originally designed.
Lastly I know there has to be a special gear box sprocket tool to take off the round nut holding on the sprocket. Does anyone know a part number for one of those (since alot of the parts suppliers are dummies when I ask them these questions without a part number)or where I can get one? Hope someone out there can help me! Peter
Why I think I'll just hop on the B33 and drive down to look at that chart. But wait I need to get that pesky sprocket problem solved first. Would a 20 tooth engine sprocket and a 19 tooth gear box sprocket make much of a difference than the stock 19 / 19 combo? About the only other size I can find for the gearbox sprocket (in my limited searches of the web) is a 17 tooth one. :rolleyes: Peter
Peter ... There is a 'hook spanner' that fits the sleeve gear/sprocket nut you speak of. However nearly everyone uses a 'soft' brass drift and tap it on/off with a hammer. Don't forget to bend over the tab washer when reinstalling the nut. I dislike using lock tite on this nut which may make it difficult to remove the next time. And as is so typical, if the notches in the nut have been punched/hammered on before and distorted a spanner won't work very well. Reinstall the rear chain to allow you to hold the sprocket from turning when doing this. Generally just the inertia of the rear wheel will hold things in place, but you may need to reconnect the pedal and hold the rear brake on.
Now is also the time to replace the largish countershaft sprocket seal that's secured by the snap ring behind the sprocket. A hint here, always smear a good coat of sealant around the flat face of the new seal that bears against the bearing race before installing the seal. It's a funky setup. Then of course grease the seal lip with grease when assembling.
The best fix for this pesky seal leaking is to replace the sleeve gear bearing with a 'sealed one side' bearing as I and many (most?) others have done. The complete tranny will need to be removed to allow you to heat the case to remove/install the bearing. But, reinstall the seal under the snap ring for proper location of the bearing.
Now I'd betcha a good part of your oil leak problem is what I and most all other pre unit BSA guys deal with, the 'Official BSA chain oiler'! There is no seal on the mainshaft where it passes through the sleeve gear. As the shaft and sleeve gear rotate at different speeds except in 4th, oil seeps out between the two. This is especially bad when the bushings in the sleeve gear are worn, oil continuously seeps out past the main shaft when in neutral or any gear other than 4th. The oil drools onto the sprocket and spews onto the rear wheel. Overfilling the tranny oil or using too light a grade oil in the tranny will cause even more leakage. Don't pay any attention to the level plug in the tranny, but with the bike level and not on the side stand, only add enough oil to cover the end of the layshaft as viewed through the oval filler hole. I use 90 wt gear oil but I'm sure 50 wt engine oil would be OK as was OEM prescribed. Be paranoid, check your oil level often!
Too low oil level is the reason there are so many fragged out bushing layshafts in bikes like your B33, vs the "T", GS tranny setup with Torrington needle bearings on the layshaft which are more forgivable of low oil.
I would suggest you find a 19T countershaft sprocket for riding the bike on the road. It should work just fine with a 19T or 20T on the engine. I too have had problems locating 19T sprockets for the narrow 520 chain as I/we use to allow fitting a sealed DID "X ring", (good stuff!) chain on the road GS and for the GS racer using narrow chain. I've had a machinist friend narrow good/new 530 sprockets a couple of times, but....
One of my problems locating narrow sprockets has been simply I don't have a parts book listing them by part number. Can anyone help me with pns for all the 520 sizes made? They must be listed in the B33 parts book... Thanks. dave - NV