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  1. #1
    Blackhardt's Avatar
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    Help with a backfire

    A friend of mine is working on a 95 GTX with the 657 engine. The engine hasn't run right since he got it. It had a bad high end bog. We tooks the carbs off and rebuilt them. After that the PTO cylinder wasn't firing. Pulled the carbs back off and found a peice of paint that had flacked off the body of one of the carbs. Got that cleaned out put the carbs back on and running but now we have a backfire through the carbs. Now I havn't seen this backfire so I am assuming that it is just vapor and not actually fire coming through the carbs. Someone had told him that the rotary valve is the problem. Since we didn't have the backfire before building the carbs I don't understand how the rotary valve could have gotten buggered up. Anyone have any experience with a rotary valve engine having this problem? I'm hoping to learn something here. Thanks, Karl


  2. #2
    96XPSS's Avatar
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    Did you guys pull the RV cover off when you pulled the carbs?

    Did you check the compression in both cylinders?

    Are both spark plugs getting wet now?

  3. #3
    Blackhardt's Avatar
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    No we didn't pull the RV cover off. I don't know if he checked compression or not. I havn't been down there during the whole process and as far as both plugs being wet yes.

  4. #4
    96XPSS's Avatar
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    Check compression to make sure you haven't seized a piston. If one cylider only has compression it will backfire just like the RV timing is off.

  5. #5
    Blackhardt's Avatar
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    Yeah that was sort of my thinking as well. Thanks for the info.

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