250x Help

[RichM1983]

Hey everyone I need help with my brothers 250X. It has a 86mm big bore kit on it but the problem is that the cylinder needs to be bored over to get the bike running again because the compression is to low. Its currently at 60 psi. The piston I currently have is an 86mm JE piston but they dont make them anymore. Does anyone know where I can get a piston thats bigger than 86mm for a 250x or 300ex cylinder? I have heard of a Turtle Racing Engine in a 250X but I cant find them online. If anyone can help I would appreciate it because I dont want to put the standard bore cylinder back on.

I thought about putting a 400ex piston in the bike but the end of the rod is a bigger size than the 250x. I think the X is like 17mm and the 400ex is like 20mm. I was also thinking about a 350x ATC piston but I dont know. Any help would be appreciated. Thanks everyone.

[GPracer2500]

Stock 250x piston is 74mm. 86mm is HUGE! Didn't know anyone ever made them that big....

If you can't find what you're looking for then you may need to re-sleeve the cylinder so you can run a piston size that's still available.

[RichM1983]

Originally posted by GPracer2500
Stock 250x piston is 74mm. 86mm is HUGE! Didn't know anyone ever made them that big....

If you can't find what you're looking for then you may need to re-sleeve the cylinder so you can run a piston size that's still available.


Yeah I hate to do that. I have a complete spare stock top end that I could use but that would be a crappy way to go considering what I have.

Your right the 86mm is huge. Its funny to compare the 86mm to the standard size.

Anyone else have any ideas? Im desperate. I was so desperate I actually baught rings for an 86mm 400ex piston and tried that and its still not getting compression so Im sure the cylinder needs bored and an 87mm piston. I can get a custom pisont from JE for like $700 but theres no way I can go that route.

[RichM1983]

By the way 86mm is huge but I have heard of bigger, I just cant find them for sale from anyone.

[2muchquad]

i have the same kit in my 300ex.I got mine from scott smith racing engines.(formerly pro fab atv).Hopefully this piston is still available or im gonna have to do some research when its time for a topend change.:(

[RichM1983]

Hey 2muchquad do you have a number to get a hold of them. I tried to call pro fabs number and it wouldnt work and now i cant find that scott smith racing engines number. Thanks.

Oh and if you dont mind me asking how much did you pay for 385 kit from ebay? I found a post that said thats where you got it from. Also how powerful is it? Really nice? Ive never even road mine yet because the cyilnder was messed up from day 1. Thanks again.

[dork]

FST has 86 and 87mm pistons, but he usually runs bigger wrist pins with those kits. but i'd check anyways.

you can always have one custom made by a machine shop


its not to expensive