Piston, when?

4 replies to this topic
  • mike_dean

Posted July 25, 2002 - 01:18 AM


When would you replace your piston as regular maintenance? '00 426, over 200 hrs, engine has never been apart, runs great. thanks mike

  • John_Lorenz

Posted July 25, 2002 - 04:32 AM


Intresting question

I was just going over the Maint Schedual per the Yami Manual.

If I remember from last night I think it said
every 3rd race or 500 or 1000k to inspect / replace if needed.

So this brings up agood point.

Who follows the recommended Maint schedual / chk as perscribed by the manual.

Opps dang fat finger hit return to quick

I would say if it aint broke dont fix it. If compression is well in the standard and no smoke is seen, then why ?

But then again, I am a tinkerer and plan on an engine tear down this Winter.

Why a engine tear down, Check trannie, clutch, oil pump, crank piston and valves to specification.

Who knows I may just bore it to a 440 :)

[ July 25, 2002: Message edited by: E.G.O.**** ]

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  • Ga426owner

Posted July 25, 2002 - 04:42 AM


I just had my top end done on my 01 with about 150hrs. I noticed a decrease in power & that is why I did it.

  • Shawn_Mc

Posted July 25, 2002 - 09:33 PM


Pistons can get fatigued. If you have been racing it hard, you might want to do a piston. I doubt the bore would need work. Basically what Id call a "top end refresh". Id be more worried about the valve springs. They are much more likley to fail.

Its surprizing how much new valve springs will improve a motors manners. When I was racing super stock flatbottoms, we'd change the springs twice a season. And after the races we'd pull the push rods, so we wouldnt have one or two hangnig open, sacking out the spring. Just food for thought.

  • MikeOK

Posted July 25, 2002 - 01:54 PM


I rebuilt mine the first time at about 150 hours. It didn't need it. If I had it to do over again I would have waited until the compression didn't spec. One thing I found out is that the cylicer at 12.5:1 compression is much more critical than on a 2 stroke. If your new piston isn't just right you will have problems and have to either have it replated to match your piston, or go with the pricey stock piston. A good compromise would be to do a new set of rings if your compression is okay.

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