Ok, now that I have all your undivided attention, here is the deal.
I own an 86 r, and my friend recently bought an 89. Mine is .10over with a paul turner T-6 pipe and fmf silencer. His is .30 over with CT pipe and silencer.
His has an unbelievable amount of low end more than mine! I am getting pissed that he is blowing me away off the holeshot every time, so I rode it, its like a night and day difference. His is almost like a damn 4-storke, the power is just there, while mine you have to wait for the power to hit. Is it the pipe, the extra bore or what?
He also has a 39 tooth rear sprocket.

 

I doubt the bore has anything to do with the extra power in his motor. It his motor "fresher" than yours? Meaning, less wear on his piston and rings compared to yours?
A pipe can make a huge difference on what RPM range in the powerband is affected. Does he have different reeds or is his cylinder ported? Maybe he has more compression than you. Compare head gasket thickness. Maybe his engine/carb is just perfectly dialed in compared to yours. The point is that there are many things that could cause your engines to produce different power. Gearing/sprockets and tires also have a lot to do with power and top speed.
One last question, are you faster on the top end than his?
ERIC

 

Ok, his cylinder isnt ported, mine is supposed to be. The guy who sold it to me said it was.
Also, his carb and engine arent dialed in, he needs to rejet badly!
Mine does need a rebuild, so that could be the problem.
His is also faster top end I think. I dont know for sure, cause once we get there he is so damn far ahead I cant tell. But I think they are very close, with his having a slight edge.

 

I've done a few motors recently that were "ported" according to the old owner. When I got it apart and look at the port job....well....Basically all that was done, was a slight amount of material was removed from the transfer tunnel dividers, or it was knife-edged(not good).

Have you taken into account traction and rider weight???

A loose bore will lose alot of power as well....

 

The Paul Turner type 6 pipe is supposed to be a low/mid pipe. More than the CT National Midrange (if that is what your friend has). Either your cylinder is ported for top end, your cylinder is badly needing a rebuild, or both.

 

The 86 and 89 motors are different as well. In 88 they swithced to a long rod, so that might have something to do with it as well.

 

When I finally fired up my 250R this summer, it did not have any power, especially down low. Then I had the motor done. It was in dire need of a rebuild. The difference was night and day.

If you are in need of a rebuild, then your motor will not have the suction at low rpm's to pull the motor. Mine would hardly idle before the rebuild. REP out of MA did my motor. And a fellow racer was pretty mad after the first race. He rides a 400ex and just could not touch me coming out of the corners.

 

SaMsOn, you're very close. The long rod motor actually started in the 1987 250R. The ATCs and '86 are the short rod motors. As for rhino99's pipe, the Type 6 pipe has THE MOST lowend of any "R" pipe. I will hazard a guess that your porting may be mid-high oriented while your pipe is low-mid OR you're in need of a rebuild. Do you SHORT SHIFT your quad. The Type 6 requires a different riding style than the mid-high pipes. You may not be using your powerband to it's potential. In a drag race on hardpack, I have to start in SECOND gear---in first my "R" will touch the ground with the rear grab bar(13/39 gearing--same as yours) when I dump the clutch. I'm not exaggerating , I've scared myself a few times until I figured out the technique! Try starting in second just to see if it helps.

 

How does your 250 R compare to your Banshee in the power department. I have an 88R that is stock and a Paul Turner piped Banshee. I love the Banshee power. Can I get close to that with my R?

 

I have not yet had a chance to actually drag the two machines in the open. But from a seat of the pants feel on the track, I would say yes.

In a drag from the starting line to the first turn, I would give the results up to the rider. If not a little more to the 250R. I think the power of the motor I had done is awesome. REP did a terrific job. I still think the Banshee has a little more in the mid and top, but the power of the 250R is constant. Much easier to get traction and keep under control.

This was my biggest fear when I started racing the 250R. Was there going to be a noticeable power difference from the Banshee? After having the motor done, this fear no longer exists.

I have a friend that races a stock 400ex. During the last race, he was quite mad. There was no way he could keep up. He said that I would just pull away from him coming out from the turns. Needless to say, he is getting his motor done this winter.