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Author Topic: Top end rebuild questions  (Read 529 times)

Offline Sandslinger

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Top end rebuild questions
« on: June 30, 2018, 04:37:59 am »
Hey guys first post here. My riding buddy has a 91 lt250r that I have been working on for him. I have owned and rode banshees all my life so am familiar with 2 stroke engines especially banshees but am trying to get this right for him.

When he bought the bike it had a bad base gasket leak from a broken stud. We pulled the jug and fixed it but noticed it had a about .060 copper base gasket under it and the piston didn't quite reach 0 deck. We put a standard base gasket on and piston was out of the hole about .030. We put on a cool head and ran it this way since last year. Last week in Silver lake he seized the top ring and lost compression. I have it torn down and the head dome doesn't look too beat up But appears to have been making some contact. Is it normal for piston to stick up a little or what can I do to remedy this. Custom cut domes?

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Offline Q2W

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Re: Top end rebuild questions
« Reply #1 on: July 02, 2018, 11:42:40 am »
They had the thicker base gasket to get the proper squish clearance.  That poor thing was probably detonating like crazy.

most people set the squish between .005 and .006.

It probably had to be decked at one time.


Offline All American

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Re: Top end rebuild questions
« Reply #2 on: July 17, 2018, 12:52:24 am »
Those marks on the dome you see are NOT from the piston hitting it,... but rather a serious detonation issue in it.  These marks often look like an impact but are just premature detonation of fuel and air.
1-1985 SUZUKI LT250R
1-2013 HONDA TRX450ER

 

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