RM 250 shift fork

[acw592]

I got the cases split today on my 97 RM250. I wanted to replace the 1st,2nd gear shift fork while I was in there, but I'm not sure which one it is. I tried to figure it out by the manual but I'm still stumped. With the gears still in the left side of the case, cylinder facing up, there is a left and right fork shaft. The right shaft has one fork and the left has a upper and lower. Which is the one I'm looking for? Thanks!

[crfjedi393]

I've only dealt with the transmissions of my CRF's so I'm hesitant to tell you that I think it's the one with the single fork. Or the "right" one. Explore the diagram on this link. Maybe it will help you. If this doesn't help, somebody will eventually step up and give you a definite answer.
BTW, this picture is like you're viewing it from inside the case. I don't think it's an outside view so it seems backward.
[Only registered and activated users can see links. ]

[crfjedi393]

I'm wanting ossa to see this one.

[acw592]

anybody on this one? I tried looking at the manual again...I'm still not sure.

[ossagp]

I never give fast answers. But I am tired so I will this time. If you want to replace the forks that control gear 1 and 2, they are the forks that move the gears on the coutershaft.

Darn, can't stop: If you notice, low gear is part of the mainshaft, so no engagement of the gear is necessary on that one. Second gear on the mainshaft is splined, and has no dogs or sockets either so no movement to engage that one is necessary.

Low on the countershaft is on the extreme right side, and second on the countershaft is on the extreme left. They must each have a different gear moved to engage them.

Transmissions are built with the two gears with the biggest size differencial on the outsides of the shafts in order to be in the positions that can take advantage of the part of the shaft that is most supported and rigid. If you put them closer to the center they would be more likely to flex the shafts apart and all the attendant problems that would bring. The higher gears which do not multiply the torque as much (or at all) are closer to the center.

[acw592]

Andy, I don't claim to be the smartest guy there is but I'm still lost. I would like to understand the gears the way you do (hope to soon). I try to look at the gears on the 2 shafts, shift forks and shift drum then try to understand the basic principle. Sorry, I appreciate your answer and know it must be frustrating when you try to explain yourself and somone like me doesn't quite get it.

[ossagp]

you want number 1 and 2 forks. It would be easier if they showed you the shafts, forks, gears, all in on picture. the first motorcycle transmission i got to see was one that was split horizontally. that used to be really common. If you ever get a chance to buy an old horizontally split case do it just so you can take it apart and look. you can keep everything in the bottom half of the case and make it shift and do all the things it does in the frame. I got to see a suzuki x6 that way. my honda xr500's are that way.

[acw592]

THANKS!!! I appreciate you guys!