What exactly does this kit do? Does it require boring or anything?
I am gettin a 250r, and want to race it, but I dont want to race open class. Can I still race the 250 class with this mod?
How much power does it add?

 

The only long rod kit that I know of is to put the '86 rod in the 88-89 engine. We have done this on one engine and still run the 88-89 cylinder put you must run then the 86 piston. There is a change in the intake and exhaust timing I think. The advance to doing this is that the 86 pistions go to a 14th over and the 88 only go to a 8th over. You can can do the same on the 88-89 engine and noy change rods, but add a spacer plate and then run the 86 pistons. I have done this on a different engine. I do not know which is the better way. Both ways helps on the low end. I do know of some long rod kids for the Yamaha's, but not for the Honda's.

 

Ok, I was told the opposite! I was told you take a '86 and put in a 87-89 rod, then the spacer plate etc!
So which is is?

 

You use the longer 87-89 rod with 86 piston which has a different wrist pin location, longer base dowels, and the spacer plate. Most of the parts are available from NAC'S(1-914-246-3086). I have heard this setup is more likely to blow out base gaskets. This setup is supposed to add about 15cc to a stock bored engine due to the longer stroke(I have heard). It should give more low end torque and advance the port timing a little but it also eats a lot of gas.

ERIC

 

The 'long rod' mod for the 250R is simply using an '87-'89 rod with an '86 style piston and base spacer plate. The '87-'89 rod is 5mm longer than the '86 rod, but there is NO difference in stroke. The stroke is still 72mm with either rod. The only way to change stroke is to have the crankshaft pin moved outboard to increase stroke. There is no danger of blowing base gaskets when assembled properly. It also does not change port timing. The port timing remains the same, but the crankcase volume is increased moderately. The advantage to the '86 style piston is that it is slightly lighter. And gas consumption has nothing to do with rod length.

 

I put the spacer plate and '86 style ceramic coated Wiseco in my 1988 250r and it made a differencein low-end. You'll need to go up 1 tooth on the front sproket. I just need to buy a bigger carb to get more top-end. Any suggestions on a which carb to buy? 38mm pwk a/s?

 

Nothing but good things to say about the 38 PWK A/S's. There should be a thead in the Perf. Forum about this....something about Keihin carbs....

 

Ok, so if this is done, can you still race 250 class in GNC races?

 

Without a doubt you can run the 250 class. The stroke length doesnt change. Rod length NOT stroke gets longer with the '87-'89 style rod. Stroke is still 72mm. As long as you stay in the AMA max allowable overbore, you are 250 legal.