Vintage Dirt Bike Q & A

I am trying to put together an engine for a 74 250M elsinore.

Some questions some one here might know the answer.

1. The cases have a gasket between them. I know the cases now just yamabond or honda bond. Should I use the gasket or not? If I use it should I use some gasket seal?

2. I am going to try to use a tranny out of a 76 Cr 250. I think it will fit. I also have a tranny from a 74 cr 250m. Which one is best?

Thanks

Yes you must use the gasket otherwise you will have clearance issues. You dont have to put any sealer on the gasket but I always use copper spray stuff on mine just to make sure it gets a real good seal. I think the 76 and 74 tranny have a differnt bearing on the output shaft where the shaft exits the motor. If this is the case the gears can be removed from the 76 shafts and put on the 74 shafts. I have a 76 mr250 tranny in a 74 mt250 and I ran into this problem but the shaft swap was real easy to do I then had it back cut and it worked real nice. I have also read the 76 had a little better tranny in it also if you dont get the tranny back in the case all the way its gonna burn it up. The shift drum has a press fit bearing on it, I used the crank to press it in most of the way and then took the case back off and gave it a whack with a dead blow and it seated it all the way. I didnt do this the first time just used the cases and thats why I had to get another tranny.

You should be good to use the 76 transmission. The countershaft is the same part number. Like Woosh said the MT250 has a different bearing on the countershaft. I think it is because of the extra gear to run the oil pump.