TRX250R bore to 265cc, Different Plug? Rejet? What do I need to change?

[395Rider]

My cylinder head is currently at Phat Head's in Riverside and I am getting it bored out to be at 265cc. I normally race the ITP QuadCross, WORCS, and MX at RaceTown 395. For my type of riding, what difference will this type of work do and what do I need to change?

Do I need to use a different plug?

I didn’t get it ported, what will this cause?

Should I use different front and rear gears?

Can I start running a 50/50 mix of race fuel and gas?

Will my engine be prone to overheating?

What size tire do you recommend for MX? Ive been running the meats it came with.

What Reeds do you recommend?

Please let me know!

Adam The Victor Villain
www.myspace.com/395rider

[400exrider707]

Originally posted by 395Rider
My cylinder head is currently at Phat Head's in Riverside and I am getting it bored out to be at 265cc. I normally race the ITP QuadCross, WORCS, and MX at RaceTown 395. For my type of riding, what difference will this type of work do and what do I need to change?

Do I need to use a different plug?

I didn’t get it ported, what will this cause?

Should I use different front and rear gears?

Can I start running a 50/50 mix of race fuel and gas?

Will my engine be prone to overheating?

What size tire do you recommend for MX? Ive been running the meats it came with.

What Reeds do you recommend?

Please let me know!

Adam The Victor Villain
www.myspace.com/395rider

I'll give this a shot...

Plug Im not positive but I would say no, ask the people doing your motor work, they would know better than anyone

No porting wont do anything, just less power than if you did. Biggest gain on a two stroke in my opinion is porting.

Gears will depend on power increase and mostly where your riding and the conditions. Some people change gearing for every race

50/50 would be a waste of money if you dont need it. Im not sure on your engine specs so ask your builder.

It will probably run a little warmer. The fuel is what is going to take care of this, if your high compression now you will need that race gas. Proper fuel/jetting will prevent overheating so again, I either need more info about the engine specs or you can just ask the builder

What meats came on it? Its preference for a lot of riders, but what are you going for, the best of the best at whatever cost, a tire that lasts a while? A compromise? On those machines I love grooved turf tamers on the rear and holeshot MX fronts, but again its preference and riding terrain also plays a role.

reeds... VForce hands down.

[86 Quad R]

is the cylinder a stock port? what bore is it on now? what pipe, carb, intake and all are you running?

[395Rider]

Originally posted by 86 Quad R
is the cylinder a stock port? what bore is it on now? what pipe, carb, intake and all are you running?


The cylinder was stock and this is the first bore. Never been ported and will be ported in the future. The current pipe I'm running is a Paul Turner Low Mid Range Pipe. The Carb is a Kiehin PJ 36mm and the intake is a HA-4250 K&N Air Filter. The Tires are ITP HoleShot 20x11-9 H-D rears and 22x7-10 XC fronts.

Please let me know your recommendations for MX racing.