I am having my 1998 Polaris Xpress 300 bored out. I am replacing the old manufacture piston with a Namura .020 Piston Kit.

DOES anyone know what the proper clearance should be????

I will probably have to call Namura tomarrow and find out, didn't see it on the box. Has anyone had experience with replacing their piston/s with a Namura piston in ATVs.

Thank YOU!
Kelly

 

Each manufacturer has their own tolerances,BUT I wouldnt go over .002 final clearance on piston skirt to cylinder skirt,PLUS check ring end gap after boring and honing. Normally about .008 minimum gap between ring ends installed in cylinder

 

Thanks for the reply OPT

 

the clymer manual says
piston clearance .0012"-.0026"
ring end gap .012"-.022"

 

the clymer manual says
piston clearance .0012"-.0026"
ring end gap .012"-.022"

 

IF you go anything under .002 you have to break it in right for it to last a long time.

 

I am asking the same question about my 2001 Polaris 250 trail blazer. I am having it bored and new piston. What is the piston to cylinder clearance and ring gap? Also how much can I remove from the head to clean it up?

 

By the book on the EC25PFE 250 engine. Piston to cylinder clearance: .0011 - .0021. Ring end gap: .009 -.018 Wear limit on piston .006 max! First tank of fuel needs to be premixed at a 50-1 ratio of gas and oil. I always tried to hit around .0015 on bore jobs as I usually ended up breaking these engines in myself. You don't have to baby them,just vary your throttle and NO full throttle for around an hour or so. I always let them run a little at first for several minutes and let them cool down,then ride em around for break in. Max I'd go on shaving the head down is .010. If .005 will clean up the head if it's been peppered with piston fragments,good enough.

 

Thanks old polaris tech,another question about assembly of the jug. What oil should be put on the pistonand cylinder?

 

Just plain old 2 stroke oil is fine.Make sure you pour a small amount in the holes of the case to lube the crank bearings and a little around the lower rod bearing area on the crank. Just enough oil so you don't have a dry start up.