How far can you bore a 250R cylinder?

A circlip came out this weekend and the wrist pin made two nice DEEP gouges in the cylinder wall.

Thanks for the info!

 

On the Honda post I answered you already, but here it is again. Since you included the year of your quad, the correct answer is 68mm. Did I BECOME A MILLIONAIRE?!?

 

I'm at 68.75mm and have 2 "safe" bores left, beyond that your pushing it. So a 88 cylinder can safely be bored to 69.25mm. Which is a tad over 270cc.

 

LT250R_86, what piston are you running in your overbored 88 250R? I have not seen a piston(Pro-X or Wiseco) listed in catalogs for '87-'89(long rod) that goes over 68mm. Are you running the '86(short rod) piston with a spacer plate? The '86 piston IS LISTED up to 69mm. Help inform me please.

 

mindcrime'
you will have to run a 5mm spacer plate to run the larger "86" style pistons that Pro-X and Weisco makes.68mm is the largest long rod style.

 

Yup, I run a 86 ProX piston with a 5mm spacer plate. Its a MacDizzy 270 Kit. Rick did the motor.

 

YUP, that's what I thought! I first learned of the ole 5mm spacer trick on my old CT310(295!!!)kit with its '86 style piston. Thanks for CLARIFYING for the under-informed! Later.

 

Is a '86 cylinder the same as a '87-'89 cylinder or are they different? What i want to know is can you run a '86 cylinder on a '87-'89 bottom end with a '87-'89 piston. or run a spacer plate on that set up with a '86 piston.

 

The cylinders ARE DIFFERENT on the '86 vs the '87-'89. The main difference being two webs in the intake to help keep the rings from expanding as much AND improvements in the exhaust porting were incorporated into the later years cylinders. You can use the '86 cylinder on a '87-'89 lower. If you use the '86 piston you will have to run the 5mm spacer plate---you don't with the '87-'89 piston. The reason for this if you didn't already know was in the '87 and up motors, the ROD LENGTH was increased 5mm and wrist pin hole was moved up 5mm. This is why the later models are referred to LONG ROD motors. Honda did all these improvements to improve overall reliability. The short rod motors are said to be more PEAKY(read more HP) and many prefer them in most racing applications other than XC racing. The long rod motors had a smoother and longer "PULL" in their powerbands and that is why many prefer them in the woods(read more torque). Hope this was helpful!

 

I had an atc 250r and I`m pretty sure it was borable to .140 over. Wiseco piston.