Vintage Dirt Bike Q & A

I thought I had a 75 CR250 tranny for my 74 CR 250M. I found out it is actually a 75 MR 250 Tranny.

Will that fit into the 74CR250M case with no problem? I also want to use all the clutch, kick starter etc gears off the right side.any issues with these?

I will be running it for MX. Will the gear ratios be unberable for racing? I do have another 74 CR250 tranny but I heard those were not very good.

Also what kind of ignition would be best for this bike? I heard the points were nothing but problems, PVL ($$$)?

Thanks for the help.

I have been told the mr tranny is no good as it drops you below the power band every time you shift where as the cr shifts right into it. I have one in my mt250 but its has a cr cylinder and a wild port job. I really like it in mine but my bike pulls pretty good in the lower revs now, well better than it used too. Also as far as I know the 75 76 trannys are better but I dont know how much I dont think a lot.

As far as racing MX goes, the MR is a wide ratio unit more suited to enduro/desert racing. A lot of people had trouble with 3rd gear on the early CR transmissions. While that disengagement problem is not present with the MR transmission, reviewers of the MR didn't like the gap between 2nd and 3rd gear. I think all the parts you asked about can be used with your engine. And as far as ignition goes, a lot of people swear by PVL, but I can't justify the huge cost and I've had no problems with points ignition. I occassionally ride MX with an MR transmission, but I'm not racing anyone but a few friends and I'm not under any illusion of beating them on their new Big Boy bikes. A 75-76 CR transmission is probably better for what you want. Or if you have the original transmission and third gear is still in good shape, you can get it undercut a bit and solve most of the problems people had with the early trans.

See this: http://alp-sys.com/vintagedbforums/view ... 28&start=0