250x help

[RichM1983]

I am having some serious problems with my bottom end. I pull the motor because of low compression, it was like this when I bought it, and has never ran for me. I sent the cylinder off to be bored and it should be ready in a day or so. Well I started working on the bottom end today. I took it completely down to the tranny because the cases had some troubles to. Well I get the tranny, crank, counterbalancer and all that put back in and put the cases together to check and see if it will shift right. Well I figure out the shifting and it seems to be working fine.

My problem is this. The entire crank assembly, not just the rod, has side to side play in the cases. I thought that something was wrong with the crank due to the play. Then I notice that my counter balancer has the same amount of side to side play, as well as both tranny shafts, the shift drum, and the reverse selector rod.

I know that both of my cases are 250x cases but I dont know if they are from the same year. Could two different year 250x cases cause the problem? Are the bearings for certain years different thicknesses? I just can't figure this out and its giving me fits. This is the 3rd 250x I've had and the only one that has gave me trouble like this.

Please help!!!!!!!

[RichM1983]

Bump

[RichM1983]

No one has any idea?

[300ex_#387]

The only think that I can tell you is that the 250x motor never changed.

[RichM1983]

Originally posted by 300ex_#387
The only think that I can tell you is that the 250x motor never changed.


Kinda thought that. Ive abadoned that idea. Im building a 300ex bottom end. Will the whole 250x top end with a 12:1 piston work on a 300ex bottom end? Thanks.

[2muchquad]

Yes it will work.It'll have a bit higher compression but you'll still be fine with pump gas.With the "actual compression" of your set up,93 octane will be fine;) .Topends between the 2 motors will interchange,not cranks etc.

[dork]

regarding your clearances, the crank should fit tight (press fit) in the left main bearing and the right should slide over with little resistance. your counterbalancer and trans. shafts should slide freely on both sides like you mentioned, so they're ok.

[bwamos]

A 12:1 250x piston on a stroked (300ex) crank will bump up compression a bit. 12:1+ compression will not run on pump gas in a 300ex.

11:1 is pushing it on a 300ex w/ port work and an agressive cam.

It should work fine, but you are going to have to run race fuel, or a 50/50 mix. (no, octane booster will not cut it).

[2muchquad]

A 12:1 250x piston on a stroked (300ex) crank will bump up compression a bit. 12:1+ compression will not run on pump gas in a 300ex.

Race gas ISNT a necessity when running a 12 to 1 250x piston in a 300ex.Actual compression wont be 12 to 1 plus once "cam overlap" is figured into the equation.;) 93 oct is fine,been running it for years

[RichM1983]

Thanks for the replys guys. I really appreciate it. I finished putting together the 300ex bottom end and everything is going well. The top end should be done by now but no calls from the shop doing the work. I guess Ill have to give em a call and ask. I should have the motor done and hopefully runnig this weekend. Thanks again for all the help. Im sure Ill be back with more Q's because I'm new to the 300ex and when I look at that wiring harness its pretty scary looking, lol.