Topic: Jumping out of second gear...

[KB02]

Okay, as the bike is just about ready to get out onto the road, I have noticed that it is jumping out of second gear when I am accelerating hard. When I am going slowly (or moderately) it doesn't seem to be a problem.

When I bought the bike, this was a known condition. When I rebuilt the engine, one of the shift forks was practially destroyed (really, REALLY worn) and so I replaced it. Everything else in the tranny seemed to be within spec. I had hoped this was going to solve the problem... apparently it didn't.

What should I look at first? I really don't want to pull and tear apart the engine again. Is there any hope for me?

... other than driving slowly in second gear?   

[bwaller]

I hate to be the bearer of bad news, but usually the problem led to replacement of the shifter drum, one fork and worn dogs on a gear or two on the countershaft I believe. It's been a while.

If when you had it apart you didn't see any damage on the drum or rounded off dogs, then maybe remove the transmission cover first and recheck the drum end screw is tight etc.

[MRieck]

First to second is a long distance. I'd agree with bwaller and suspect the drum and/or dogs. If you undercut the transmission you can usually save the gears.

[nteek754]

Yeah hate to say it but Im betting it is the drum 20 years ago I had one jumping so tore it apart  I had three of everything extra  so I picked and chose well I put the same drum back in not realizeing that was the culprit  but from what your saying of one of the forks tells me it hasnt been in sink for a bit like the gear has been resting on it and not all the way in them damn worm holes in the drums are the hardest to notice if they are good or junk  find a junk engine and  grab the tranny or ebay but thats a long shot on the drum good luck seven fifty four ever

[KB02]

  ...I don't wanna pull the engine... 

I'm hoping it's just the loose screw, but if I do have to pull the engine apart, can I just split the lower half of the crank case and leave the top end alone? Or do I have to pull the whole thing down?

[bryanj]

Did several back in the 70's and as a "customer" job we always relaced drum, selector, gear the selector moves (5th I think but brain is old) and BOTH gears it mates into (via the dogs not the teeth!) and yes you can leave the top end alone