GZ 250 Forums - View Single Post - Piston-Head interference Issue

**jonathan180iq** · 12-19-2012, 09:32 AM

A warped head could have caused the low compression, and maybe the intereference..... But I would suspect the weakness and the leak would show up near the outer edges and not something that caused contact right in the middle....

Without knowing the history of the Ebay motor, and since I don't know what the specs and tolerances are for the engine of how to check it at this point, there is really no way of knowing what caused the contact between the piston and head. If you said the lateral play was within spec, then there is no reason to question it. (Maybe check it again, but it sounds like you know what you are doing.)

The condition of the original bottom end must still be good, right? You could mate the original bottom with the new, machined top and see if you have the same issues... If there was too much lateral play in the new connecting rod, then perhaps that's not an issue with the old motor. And since you know you'll have a planed and mated surface on the new head... Well, it's worth a shot. Otherwise you're just back at square one, kind of guessing at what caused the issue to begin with. These things are usually pretty bullet proof, except for a few common issues that aren't what you are running into.

12-19-2012, 09:32 AM	#2
jonathan180iq Super Moderator Join Date: Jan 2007 Location: Dalton, GA Posts: 3,995	Re: Piston-Head interference Issue A warped head could have caused the low compression, and maybe the intereference..... But I would suspect the weakness and the leak would show up near the outer edges and not something that caused contact right in the middle.... Without knowing the history of the Ebay motor, and since I don't know what the specs and tolerances are for the engine of how to check it at this point, there is really no way of knowing what caused the contact between the piston and head. If you said the lateral play was within spec, then there is no reason to question it. (Maybe check it again, but it sounds like you know what you are doing.) The condition of the original bottom end must still be good, right? You could mate the original bottom with the new, machined top and see if you have the same issues... If there was too much lateral play in the new connecting rod, then perhaps that's not an issue with the old motor. And since you know you'll have a planed and mated surface on the new head... Well, it's worth a shot. Otherwise you're just back at square one, kind of guessing at what caused the issue to begin with. These things are usually pretty bullet proof, except for a few common issues that aren't what you are running into.
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