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View Full Version : What piston upgrade for a 1985 atc 250sx to match my other upgrades?



86trizinger
07-08-2010, 10:40 PM
I went to put on my new exhaust tonight. As I was taking off the old one one of the studs broke off.
Now the head is going to have to come off to get drilled out at the machine shop.I plan on putting new vavles and seals while it is off as well.

This is what I have so far:
350x carb - stock 350x jets for now.
NOS Bassani Exhaust
Head is going to be freshened up with new valves and seals

I was thinking that even though it was running good to just go ahead and bore it and put a new piston in it. Any suggestions on what is a decent piston upgrade. I couldn't find any higher compression ones yet.

TheRealFatShady
07-08-2010, 11:10 PM
Higher compression pistons seem impossible to find, Skiffy found one from a member here, but I haven't seen any for sale.

I'd say just get a TRX300 cylinder, crank and rod (seen some under $50 on eBay), and then get a big bore kit for it. Or just use a stock TRX300 cylinder/piston. Need the crank, or at least the connecting rod from a TRX engine due to the wrist pin location, so pistons wont interchange.

I've seen running engines for around $150-$250 if you look around. You can drop that entire engine in, and then use the 350x carb and Bassani exhaust. But 250sx/ES pistons are hard to find with a higher compression rating it seems, so maybe a TRX top end is a better option.

KASEY
07-08-2010, 11:16 PM
i might have a high compression piston for your trike,, i will look this weekend

86trizinger
07-08-2010, 11:31 PM
Thanks Kasey.
Please PM me and let me know.

Thorpe
07-08-2010, 11:41 PM
I had found 12:1 pistons awhile back....