91 250x piston compression?

[travis12]

I am rebuilding my 250x and the only piston I found was a Wiseco Piston Kit Standard - 1991 Honda TRX 250X FOURTRAX Part# 160301 from RM they say this is a 12:1 compression piston I don't want to run race gas is this the wrong piston? Wiseco says that this is the only piston compression they make for this model. Should I look at another piston or will this one work?


Please help...

[ironman250x]

I have just got done rebuilding the engine of my 1991 250x. I found many different piston kits. Wiseco makes a stock bore, .20 bore, and a .80 bore while Sparks Racing offers a 82mm bore piston kit with big bore sleeve for about $175. This is what I went with and you do not need to use race fuel either. And trust me this adds quite a bit of an overall power gain. I think that you should pay a visit to Rocky Mountain Atv or to Sparks Racing.
www.rockymountainatv.com (http://www.rockymountainatv.com) www.sparksracing.com (http://www.sparksracing.com)

[xlr810]

Wiseco sells the same piston in 11:1-- which should be fine on premium fuel, only they list it for a 300ex instead of 250x. Either piston will work in either quad.

I was scratching my head over this as well. I found out that while not all the parts are identical, all parts will interchange from the base gasket on up between 250x and 300ex.

[travis12]

I bought the 12:1 and it would run on pump gas but smoked like hell. After redoing the valves etc I removed the piston it was 73mm not 74mm that is stamped on the piston. I installed the new rings on the old piston and now it runs good. The piston is going back.

[Jwilsonpwt]

Hey there,
I just rebuilt the top end on my 1987 250x and was thinking the same thing about the race gas. What I ended up doing was getting in tough with Mickey Dunlap at 4 Stroke Tech. He takes a 12:1 Wiseco piston and mills material off the dome until he brings the compression down to 11:1. I purchased this piston from him, replaced my valves (they were badly worn), and I am very happy with it. I run premium fuel with no problems. I had talked to Wiseco about the 300ex piston, but was told that it would not work with the 250x. The reason for this does not have to do with the bore, but the stroke. I just ran mine off again my dad's 88 250x that is completely stock, and it ran all over his. I did quite a bit of research on this before I made my decision and am very happy with the results. I hope this helps you out.

[dork]

right, the 250x and 300ex pistons are the same bore but have different pin locations and don't interchange.