My spec card for the piston says to run 30 thousandths so thats what I had the machine shop do for my 102mm JE piston in my Raptor.

Others are saying that a new batch of pistons has 40 thou spec and some say to run 45.

Do I need to go by what JE recommends for my piston, 30 thou, or have it re done with 40 or what?

Opinions?

I don't want this frigger to break a rod b/c its too tight but then why would JE recommend too tight a bore?

Thanks

 

I had mine set-up a bit loose...I don't mind doing a top-end once a year, but I don't want to go back into the bottom end

 

I feel the same way. I set mine up at 0.045" because of a recomendation by someone WAY more knowledgable than me. If you could see my piston you might lay gold brick, I laid two.[img]i/expressions/face-icon-small-shocked.gif[/img] I have VERY, VERY, VERY few hours on this piston and then my tranny took a dump. When I pulled the top end and looked at my piston I thought I got a crappy bore job. I have verticle scratches on the two sides where the piston is longest. I checked and rechecked my bore and it is 110% round, with the 0.045" clearance I requested. Thats my story, I hope it helps you decided something. If I had a digi camera I would post some pics real quick because its still out of the cylinder.

 

I would like to know more about this too, because I bought a 102mm 11:1 je piston from 14min. off of ebay some time ago and it never came with any instructions or clearance recomendations. I am getting real close to installing it and would really like to know more. Thanks in advance

 

Ward,
Just a theory. Perhaps the piston was actually TOO loose in the bore, causing it to rock back and forth in the bore and slap the side of the walls??? Who knows?

I re-verified with JE yesterday and they still call for 3 thousandths (not 30 as I originally posted) on this piston for this bore on this ATV. I'm just gonna go with what they recommend. The guy who did my bore job is a drag bike racer and set it up how he sets up his bike. His bike uses the same JE casting as the Raptor so I am hoping he knows what the heck he is doing with the set up of this piston.

What a pain in the butt. I'll let everyone know if my rod breaks!

 

I guess I had the same brain fart too. My clearances are 0.0045 NOT 0.045.

I guess you could be right about it being too loose,ahhh , who knows. I sure hope not.

 

14mins you think you could answer this post please

 

The spec card give tolerences in "PER INCH OF BORE". Read the spec card closely.....3 thousandths X 4" bore (Raptor in very close too that) would be 12 thousandths.

 

My JE piston was set up at .0045 in the bore. The paper work clearly states .003 to .0045 thousands of clearance between the piston and the sleeve. If you set it more than .0045 you might be to loose in the bore.
Now on the other hand Wiesco two-stroke piston require .003 thousands between the piston and the sleeve, but the ring gap was set at every inch of bore measured, there should be .004 thousands clearance. Example: 2.55 bore = .010 thousands ring gap.

 

Shoot man!

I guess I'll just trust that the drag racer guy set it up right!

I'll let you know if she blows up.