250R Guru's!! 86 cylinder on 89 motor?

[RUNMYTA]

I am in the process of a complete rebuild and I have a buddy that has a very fast stock bore, ported 86 cylinder that I can pick up cheap. What all is need in the swap to use an 86 cylinder on a stock 89 motor? What are the Pro's and Con's? Will it run as strong as it did on his 86?

Someone said that I can use stock 89 crank and piston???
I think I had to use a spacer plate and a 86 piston. What size spacer? Thanks for the help.

[powerslider]

The cylinder will work fine on your 89 with the 89 piston. No spacer plate needed. The 86 crank has a short rod with the wrist pin location lower on the piston. Your 89 has the long rod with the wrist pin location higher on the piston. You may need his head also if it's been rechambered to correct the compression ratio or you would have to rechamber yours to match it.

[RUNMYTA]

I talked to ESR's tech guy and he said that I would have to run a 86 piston with a spacerplate?? What would be the difference between 86 piston & spacerplate and 89 piston?

What are the benefits of each?

[powerslider]

His info is incorrect, any cylinder will work on any year, the only difference being the rod length which requires the different pistons with different wrist pin locations.

[gncc571]

If you use the 86 cyl.and want to use a 86 piston you will have to use the spacer plate.If you don't the piston will hit the head.To use the 86 cyl. without the spacer plate you will have to use a 87-89 piston.

[RUNMYTA]

So what would be the better setup? Spacerplate with 86 piston or No plate and 89 piston?

Would they be any performance gains with one over the other?

[powerslider]

The better setup??? For what type of riding/ There won't be that much difference. Using the spacer plate may lower the primary compression in the crankcase resulting in a smoother power delivery but I would build it without the plate. Your choice of exhaust will make more of a difference. There are however more overbores using the 86 style piston but if this is a stock bore you've got a lot of ride time before you have to go that route.

[AndrewRRR]

Just run a 88-89 piston, don't fool with spacer plates.
The 86 cyl can be bored .120" over and the 88-89 can go up to .080" over from what I hear.

[RUNMYTA]

I will be using the bike for GNCC/woods type racing. Is there a difference other than wrist pin location between the year pistons?

[tprender]

The cyclinders on the R's can be inter changed at will. The pistons and rods are what different. Like they are saying the wrist pins are in different locations. The shape of the pistons at the base are different because of the ports inside the cyclinder. If you have a 86 lower end you use a 86 piston. If you have a 89 lower end use the 89 piston. The 86 cyclinder will go up to 14 over bores and the 89 will only have 8 overbores. The spacer plate will give a little bit better lower end, which would be good for XC racing. But the FMF Fatboy or the Narly (I think it called) pipe will help out that.
Bottom line, get the cyclinder and use it.