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XR100 Head Gasket Issue

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I just put one of the 132cc Big Bore kits on my XR100 and after a day or two of riding what seemed to have been a strange noise undetected turned into being a leak on the right side of the engine between the head (stock) and cylinder (new).

We had put a stock head from an XR80 on the bike which ran great by the way, but this head gasket issue roared its ugly head. We fixed the valve issue in the original XR100 head and changed it out thinking there may have been an issue with the XR80 head but there was still the air leak on the right side.

My question is that I would like to try and put the original head gasket back on in place of the new one. Is there any issue with doing this? The piston is oversized and the gasket would not be but since the stock head being used I don't see that it would be a huge issue. I'm just looking for some experienced expertise to say yeah or nay.

thanks for all you help and input.

Steve

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I seriously doubt you can use the stock bore head gasket on the 132 cylinder. The dome of the piston will hit the gasket. I’ve heard of a few blown head gaskets on these 132 kits, and I believe someone cured it by spraying the gasket prior to assembly with Permatex Copper Gasket Sealer.

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It is quite a difference the amount of compression the big bore kit gives the bike. It will kick back if you don't show it some respect when starting. 👍

I had heard that the raised compression might be an issue but I hadn't seen anything in the forums about it so I appreciate your input. I hadn't seen the Permatex Copper gasket spray but I will definately get ahold of some to give it a try. I will let eveyone know how it works out.

FYI: the kit with a 26mm Mikuni carb (unsure of jetting) with stock pipe and UNI foam filter makes the bike run great. I have not had it out to open it up to see top end speed but we have a 3/8 mile track in our back yard with lots of ups and downs and the motor pulls strong off the bottom especially noticable in third gear going up the hills. I was very impressed.

The stock motor would run equally with my friends Pitster Pro 125cc on the flat straights but with the kit installed I can now pull away from him.

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The permatex coper spray sealant is made for metal head gaskets, I recently re-installed my 132 kit with it and have had no issues. Ive tried several engine combinations, and nothing breaks the rear tire loose like the 132 kit. You need to find a real performance cam, the TB cam is no better than stock, Im using a takegawa stage one.

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