3 1/2 engine rebuild

dynadavid · Post by **dynadavid** » 18 Jun 2009 10:00

Hi folks,
I have just rebuilt the engine on my 3 1/2 drum brake sport and I have a problem with gear selection. The motor is back in the bike with everything back on apart from the barrels. I followed the manual very carefully when building the moter- the gear cluster and selector forks are in perfect condition with no visible wear, the gear lever moves smoothly up/down and it returns to the centre position after selecting a gear. When I try to select the gears while turning the back wheel slowly there seems to be a neutral in between every gear and it doesn't seem as though there are 6 gears in there..

Obviously I'm a bit worried about this as I don't want to finish the rebuild only to find there is a gearbox problem that needs another strip down.
Has anybody else experienced this? Is it possible to install the gear cassette such that all of the gears can't be selected?
Thanks for your help,
Dave

stillooking · Post by **stillooking** » 18 Jun 2009 12:25

a few years ago I rebuilt my ser 1 sport; twas the first time that I'd tackled an engine rebuild, to cut a long story short before I joined the crank cases I decided to try and see if the selector would move the gears etc, I experienced problems - whether this was because I'd removed the g/shift selector stop plate when I dis-assembled it I don't know but in the end I had to admit defeat and take to NLM, which I didn't really want to do.

Was the g/box working before you stripped it? Also, did you disturb the g,shift selector stop plate when you split the cases?

gareth

dynadavid · Post by **dynadavid** » 18 Jun 2009 12:34

No, I didn't disturb the selector stop plate- I left it bolted into the rhs crankcase half. I can't figure it out- I don't even know if the lowest gear I can engage is actually first gear or not. Does anybody know how many times the crankshaft rotates for one revolution of the rear wheel when the bike is in first gear?
Thanks,
Dave

dynadavid · Post by **dynadavid** » 22 Jun 2009 14:36

Well, I finally got to the bottom of the problem- I marked up the flywheel and carefully counted crank revolutions while turning the back wheel and disengaging the clutch/moving the gear lever. The action is nowhere near as slick or positive as some Japanese boxes I have worked on, but all the cogs do seem to be there.
What threw me out was that as I had assembled it, the gearbox was in 3rd gear and I thought it was in first.

That's the theory anyhow- I have a bit more work to do before I start the motor up and go for a ride..