Pro-X piston fitment

[bainer1290]

Picked up the cylinders from the local machine shop. He said that each cylinder is in great shape and within half a thousandth. The bore in each was 84.07mm.

I think I'm going to go with the Pro-X pistons, I've done some research and it looks like the magic clearance number for them is about 0.005 to 0.006 inches.

On the web for Pro-X it says the STD piston part# 01.2514.000 is 83.91mm, so with my bore being 84.07mm that gives 0.16mm which is 0.0063 inches which I think is pretty close?

Yes or no?

[bainer1290]

Nobody is running pro-x pistons?

[WFO]

ck pm

[Duke]

Sounds like to big of clearence to me. WFO might have a little more detail on that. I ran .0038 on the OEM pistons and just a little over .004 on the Pro-X. Most people use the Pro-X and I belive is the same manufacturer that makes them for Yamaha.

[bainer1290]

Thanks for the input Duke. I had read two different articles for the ProX's. One said to go about .004 like you are saying and the other said to go around .005 - .006

I have been stuck in the middle ever since. The std size is out of stock at the warehouse anyways so it looks like I am going to have to go with a 84.25 anyways...

[Flying Scotsman]

.005" for Pro x .007" for Wiseco sounds about right to me.
Only way is to measure the piston first then bore the cylinders to size.
3 new pistons will not all measure the same size they must be matched to each cylinder.
SD.............

[OsideBill]

if you were running wiseco's before the bore sounds right. why not run them and skip the rebore expense all that is needed is a little warm up before WOT

[bainer1290]

if you were running wiseco's before the bore sounds right. why not run them and skip the rebore expense all that is needed is a little warm up before WOT

Well that does sound like a good plan Bill, maybe I will go that route just to make things easier...

But...

The new Wiseco's are .005 smaller than the required bore, so that's 0.13mm. So for STD wiseco (84mm bore), my clearance would be 0.13mm + (84.07mm bore - 84mm) = 0.20mm which is 0.0079" clearance. So is that too much also?

[bainer1290]

hahaha well here's the latest news...

Pro-X is sold out at the warehouse of pretty much every piston for the GP 1200, so I can't get them. The local dealer can get me WSM's in .25 over, but I don't really want to go with them...

The option still exists for me to go with the Wiseco's again, but I don't really want to go that route. Looks liek I'm screwed until the stock comes in for Pro-X's which isn't going to be until next spring!

[Flying Scotsman]

What size pistons do you want I went through this looking for 84.5mm prox

Got one at boats.net.

I did email Prox and I might be able to help you.

Scott.........