I just found out that i need a new piston for my 86 TRX 250R, and was thinking of buying a higher compression one for more power, since i'm prolly gonna build my motor strong anyway. What are some good companies to buy from, and what compression ratio should i go with? I still want to be able to run pump gas...just maybe a higher octane. Any Help would be appreciated.

 

There a no companies that I am aware that make higher compression pistons for a TRX250R. That's more of a 4 stroke thing. Having pop-up domes to raise the compression ratio.

For your engine there are several ways to get the compression ratio up. The best way is to the head re-cut for an optimized pocket and squish band. Most shops charge around $75 or so to do that. The gains are there, not huge, but resistance to detonation is increased, power increases, as well as fuel mileage(I know not a huge thing, but can help).

You can use a '89 CR250 head gasket which is about 1mm thinner than the OEM TRX head gasket. This in affect is the same as milling or decking 1mm off the head, but a nonpermanent solution. This will raise the compression up. If you plan to run any ignition advance with a CR head gasket I higly reccomend using at least a blend of "race" gas and pump gas to prevent detonation. I have successfully ran engines with a CR head gasket and a single basket gasket without running into detonation problems. I would however, feel safer to recommend using a blend or ggrrrrr, AvGas(no debates please.) You can also run two base gasket and a CR head gasket and run it on pump gas safely...

 

Backcountry is right - there are no high compression pistons available for the R. The cheapest and easiest way to increase your compression is to run the 89 CR headgasket like he said.

I run a CR headgasket in mine with no ill effects so far (about one year). It makes it a little snappier off the bottom but the gains seemed pretty minimal to me. I run race gas so I don't know if it would have detonation problems on pump gas or not.

If you are going to get serious in the future with your motor you should ante up and get a Pro Design Cool head. That way you can swap in different combustion chambers for different compression ratios and also have more cooling capacity.