Gearbox slips out of 2nd under load

Some Background, wet clutch,steel plates, high CR 750 C head/jugs on 850 bottom end

So If I really open it up the clutch slips a bit, not a huge deal could switch to barnett but it works. The problem I am having is that sometimes, not all the time when I am driving the bike hard it slips out of gear. It doesn't do it when I drive like a sain person however I still think its a problem. I think that the motor puts out to much torque for my old (maybe worn out?) gearbox to handle. What do you guys think?

*EDIT - Doesn't seem to have the same problem in other gears

Dave

As it only occurs when you accelerate hard then it is likely that the corners of the driving dogs (between mainshaft 2nd and 3rd) have started to round off so there is no longer enough undercut to keep the dogs engaged under load.


http://wiki.sabmagfaq.org/Undercut%20Transmission

This is why I love this forum, you learn new things all the time. Thanks for that link and info L.A.B. Cj

I guess I figured it was something along those lines, I'll just keep riding for the season unless it gets super bad and rip the gearbox apart in the fall

Without getting in there you just don't know. A cheap and easy thing to do that may or may not fix your issue is to put in a fresh detent spring and detent, at least the spring. For $4 what do you have to loose. The characteristics of these springs is that if you loose a small amount of tension (length) you loose alot of function. The least this can do is get you through the season and leave you with a fresh spring
Item 15. http://www.oldbritts.com/1972_g6.html

My first gear was jumping out under load. I changed the spring and the issue went away. After doing gearbox work later on, the gear dogs appeared fine.

changing the detent plunger spring will not do a lot
it would if one misses gears but here the box does engage but when accelerating it jumps out of gear , your dogs are shot
a bodge is to grind them with an axelgrinder , but beware not to touch the edges , to make sure all dogs engage at the same time
i check with enginering blue
remember this IS a bodge but it works if done carefully

I think your right lynxnsu, I will have to take it apart and have a look and maybe order up some parts. Know a guy who might have an extra gearbox kicking around and Im planning on going up to visit him anyway so I'll have to poke around his shop, maybe take mine with me so I can get him to give me a hand on the rebuild :lol:

Im not quite ready to start axel grinding my dogs yet.