COOKSTER

I just discovered that my "new to me" 98 ZL 500 needs pistons and rings due to a lean running condition, they are damaged at the exhaust port area. I took the top end off and the jugs are okay so I went out and bought new pistons and top end gasket kit. I just bought this sled, I have never used it myself but the guy I bought it from said he just replaced a couple of gaskets that "always go", I think he was pointing to the carb side of the cylinders but I cant be sure. Also, I found an advertisement for replacement pistons for my sled and it refered to the O.E pistons as "Failure prone".
What can you experts tell me about this particular motor? Have I bought a known lemon?

polaris rider

those were good sleds! only known issue with cats in the 90s are the drive shaft bearing failure. ask ninja, hes got a 98 zl with 4k miles and engines all original

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1999 AC zl 500, 3k miles2003 polaris classic 340 1200 miles-2003 polaris indy xc 500 1500 miles-2000 polaris xc 700 6500 miles-2003 arctic cat zl 600 1500 miles



"Dont let fear and common sense stand in your way!"

COOKSTER

Thanks, that sounds reassuring.
Based upon the failure diagnostic sheet that came with the new pistons, burning and scuffing right at the exhaust port area on the piston is caused by running too lean. I plan on checking the plugs frequently after it's fixed and being ridden to make sure it's not still running too lean.
funny how it happened to both pistons, that kind of makes me wonder?
Can leaking exhaust gaskets cause it to run lean?

RJ Gleason

Not really, jetting or leaks at the intake side can do this though.
Check the rubber carb mounting flanges for cracking or gaps against the manifold.

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Old Cat Rider
'93 Wildcat 700EFI
w/ Comet 108 Pro-4 clutch & 01 ZR skid

'90 Wildcat Project in progress.

Trail Boss; Dryden to Summerhill trail.
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Junior Warden; F&AM Dryden Lodge# 472

kccats

Now that the sled is over 10 years old you may need to replace the seals (Crank)! These were very good dependable sleds! But the engine needs to be freshened at about 3500mi! Yeah they'll run longer but then it becomes more expencive to rebuild! And performance drops off!

COOKSTER

Thanks for the sdvice.
Can you eloborate on what you mean by freshened?
As mentioned I am doing the pistons and rings... Would a "Freshen" include crank seals?

brianph09

When you say that the engine needs to be freshened at 3500 miles are you saying piston and rings or just hone the cylinders and new rings

polaris rider

rings and gaskets

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1999 AC zl 500, 3k miles2003 polaris classic 340 1200 miles-2003 polaris indy xc 500 1500 miles-2000 polaris xc 700 6500 miles-2003 arctic cat zl 600 1500 miles



"Dont let fear and common sense stand in your way!"

brianph09

should the cylinders be honed i have a 99 zl 600 with about 4500 miles or more on it and im not sure if it has ever been done but it seems to be all there as far as power goes

kingston_rider

Have a machine shop hone if changing rings to allow for proper seating, nickasil coated cylinders are easily damaged if you aren't careful.

kingston_rider

Inspect the pistons closely for cracks/wear, if in doubt, change, the tab holding the rings in position are known to fail as well causing the rings to spin and contact the exhaust port. I would also change the wrist pins and bearings while I was at it.

kingston_rider

Doing the crank seals is a major undertaking requiring the crankcase halves to be split, (machine shop/engine out of machine, complete teardown)this is only done if required, usually indicated by a lean condition on one cylinder or the other.