Unexpected modification- transmission swap

[Zyx]

Unanticipated mod:

Starting to put the model 97 engine together today, I discovered that the transmission in the 97 engine I bought is not a 97 transmission, but out of either a 100 B or Super Rat of the same vintage (1970 - 1972). Main shaft, countershaft gears, and kick start gear were replaced as a set. Presumably, someone wanted a wide ratio tranny.

Question: has anyone out there had experience with such a change? Like trying to make a woods bike out of the MX'r? This combination is probably closer to what I am used to, having run a Webco 125 top end on a 93 Rat bottom end for years, racing cross country and riding in the woods. But, the 97 top end is ported for peakier power, and might be a bit doggy on the bottom. I rode the bike only twice these past couple of,weeks before deciding to tear it down and check seals, and didn't find it all that strange to ride, but because the clutch was slipping badly, I have no real sense of what power delivery will be. Once the power peaked, the clutch slipped. But while it was not slipping, it climbed hills okay. Just didn't have enough throttle time to really tell what the combination would do.

So if someone has a sense of what a wide ratio gear set would do on a MX engine, feel free to opine.

Thanks.

[BrianZ]

I can't really speak from experience as I've never rode a 97 with the Ace gear set, but I have rode a Toad with what amounts to a model 97 top end and I can say it works pretty well. The gears are spaced a little further apart than what I would consider ideal for motocross, but it works really nice in the woods. I would hazard a guess that the reeded 97 would be less peaky than the piston port 93, but I can't say for certain as I have never rode the two back to back. The once thing I would be concerned with is gear breakage as I've broken third gear twice in my Super Toad. Does your 97 have the cushioned primary gear? If not you may want to try Paul's improved rear cush drive rubbers. I'm planning on putting them in my Super Toad once I get it going again.

Brian

[Zyx]

I have an old, non-cushioned rear hub, four bolt system from, I believe, a model 93. Primary gears between crank and main shaft are not cushioned. Didn't know there were any.