ATV engine top end overhaul...

[rusty ol ranger]

01 sportsman 500 h.o

Since i get better help here then on the polaris forums...

I found out why its burning oil like a fleeing iraqi.

Pulled the head off and there is so much slop in the bore that you can literally flop the piston around. I have no idea how it even ran....kudos to fuji heavy industries.

Anyways...

Im gonna replace the bore (jug?) And piston/rings. Trying to decide between a weisco kit (what im leaning toward) or a namura.

The weisco is forged vs namura that is cast. Ive heard horror stories on both, the weisco can cold seize and the namura can shatter, bend, and do all sorts of cool stuff.

Its obviously not a race machine and im not spending what they want for an OEM piston/jug.

All it does is trail ride and pull/push stuff.

Input from a few resident atv gurus?

 

[Blmpkn]

Wiseco always.

 

[Snoranger]

CP Carrillo... or OEM.

Wiseco is the brand name that everyone knows. That’s all about marketing. They don’t make a bad product, but it’s certainly not the best... and not what I use.

 

[sheep herder]

Swap a 2.9 in it.

 

[Snoranger]

@Dirtman style fun fact...
Fuji Heavy Industries = Subaru

 

[rusty ol ranger]

CP Carrillo... or OEM.

Never heard of CP Carrillo. Ill google them.

@Dirtman style fun fact...
Fuji Heavy Industries = Subaru

Yes, i knew this, but Fuji Heavy Industries sounds....i dont know...more bad ass.

 

[Dirtman]

Your buying pistons from this guy?

 

[Snoranger]

Never heard of CP Carrillo. Ill google them.


Yes, i knew this, but Fuji Heavy Industries sounds....i dont know...more bad ass.

I’ve used CP pistons for years now. Never had an issue. I have one waiting to go in my Grizzly 550 to convert it to a 700... I just need the ecm.

 

[rusty ol ranger]

I’ve used CP pistons for years now. Never had an issue. I have one waiting to go in my Grizzly 550 to convert it to a 700... I just need the ecm.

According to their online catalog they dont make a piston for the ol 500's.

 

[sooperxtool]

CP are probably the best. Wiseco are fine though and for that application I would likely go with whichever is the more affordable option.

 

[rusty ol ranger]

CP are probably the best. Wiseco are fine though and for that application I would likely go with whichever is the more affordable option.

Namura is cheaper the weisco. But ive also never heard of namura till i started looking at pistons

 

[sooperxtool]

That name isn't ringing a bell for me either so I can't give any input on them. Are you finding any reports?

 

[91stranger]

I've never had to replace anything like that on my atvs but my friends have used Wiseco and never had problems.... This was 10 years ago so they may have gone down in quality.

 

[rusty ol ranger]

Well i ended up ordering the weisco. Should be here by tuesday.

Hopefully i get a few years out of it. If rather take a chance on seizeing then the namura that has a history of coming apart and destroying the bottom end in the process.

 

[G8orFord]

I haven't bought a Weisco piston in about 25 years, but we used to run them in our 5hp Briggs racing carts. Never had an issue with them and they were the lightest we could find and most used by others. I never dyno'd the engines, but I'm pretty sure we were getting somewhere near 30hp out of those old tiller engines. 70mph was not a problem in the limited and open classes.