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Anyone ever see detonation do this?


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Pulling my motor apart to do the crank bearings. All was well until I pulled the head off of the jug. The bike has a 68.19 mm piston and I think it was sent to Eric Gorr for a 275. When I bought the bike it had bad detonation under load. I finally cleared that up with jetting and 100 octane fuel. The piston looks good, but the head looks like some one took a claw hammer to it. The dents are pourus at the bottom so they were not made by something hitting them, they were made from the detonation. The cylinder looks like it has some pitting as well. I think I can let the cylinder go, but I definatly need a new head. Anybody have a spare?

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I've seen it before, but there was a time when I was convinced that it was because of foreign material getting into the jug. Either a broken off piece of spark plug etc.

However, after looking at tons of pics and reading peoples stories, I'm pretty sure that detonation can gouge a cylinder head to make it look like something foreign entered the combustion area.

Detonation really screws things up!

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There is even some pitting at the top of the Jug right next to the inner oring. There is no way foriegn material could make contact there. Very wierd. I bought a head off of ebay for $50. Now I just have to figure out what piston this is. I think it is for some sort of honda that measures 68MM. I am going to try to get the case split after the kids go to bed. That is about the only time I have to work on my bike.

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