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These are the pistons from a 1996 EVO FXD 80. Pretty carboned up if you ask me. The valve relief divots are almost filled in on the rear one. Could this be the source of a tick I have been chasing? What causes this much build up in a motor that idles nice and ran well? Lacking in power, however.
Having the cylinders bored 020 oversize with fresh pistons and some head work at Hammer Perf.
Last edited by randallissimo; Jan 22, 2026 at 09:46 PM.
3 major causes: Running rich, engine vented back into to carb, or burning oil. Two of the three are fairly easy to correct. The third sounds like it will be taken care of soon.
Me too. Using oil was certainly an issue. Leak down caused air sounds in the crankcase. Valves actually seem like they are sealing pretty well still. I'm think out of round cylinders leaking. Boring them round again with over size pistons/rings should go a long way to correcting the loss of power and jet black oil.
Sounds like a good time to refresh the top end. And vent the breather away from the intake.
I prefer Cometic MLS head and base gaskets. I'd bet Hammer will check the cylinder bases for flatness, which is important to get a good seal. If it were mine, I'd check the deck height to calculate the proper base and head gasket thickness for reassembly.
FWIW - In the past, I've had problems with some aftermarket umbrella valves in EVO engines not sealing properly. I used OEM umbrella valves and rocker box seals to solve the problem.
These are the pistons from a 1996 EVO FXD 80. Pretty carboned up if you ask me. The valve relief divots are almost filled in on the rear one. Could this be the source of a tick I have been chasing? What causes this much build up in a motor that idles nice and ran well? Lacking in power, however.
Having the cylinders bored 020 oversize with fresh pistons and some head work at Hammer Perf.
Why are you letting them go .020 over? You do know, that is the end of the cylinder. (?)
If it ever required anything else, you would have to buy new cylinders.
May also want to check your valve stems/guides to make sure they are not oblong or have the machine shop check if you do not have a valve spring compressor. Might as well do it while you have it apart.
Because I trust Hammer Perf knows whats up. I've used them in the past, and they are aces in my book.
"May also want to check your valve stems/guides to make sure they are not oblong or have the machine shop check if you do not have a valve spring compressor. Might as well do it while you have it apart."
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