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  1. #1
    Having Fun jp1300r's Avatar
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    Anyone running RIVA Pistons?

    Anyone running RIVA Racing Pistons may want to borescope their engine and check the pistons. Take a good look at the exhaust side valve reliefs.


  2. #2
    Huh? Dyoung's Avatar
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    uh-oh........what happened?

  3. #3
    DaveC's Avatar
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    What is the problem with them JP ? And is it stock or over size and 8.4:1 or 9.5:1 ?

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    dnielsen's Avatar
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    Spit it out Jim, there are many of us running these! If you are having issues tell us what clues made you start looking.....

  5. #5
    Having Fun jp1300r's Avatar
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    So far 8.4:1 20 over and 9.5:1 stock bore. The exhaust valve reliefs appear to not be machine correctly. The exhaust valves are just hitting the pistons in two different engine. We measured the distance between the exhaust and intake reliefs on a stock piston and RIVA piston and there is about 80 thousandth difference between them.
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  6. #6
    dnielsen's Avatar
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    Quote Originally Posted by jp1300r View Post
    So far 8.4:1 20 over and 9.5:1 stock bore. The exhaust valve reliefs appear to not be machine correctly. The exhaust valves are just hitting the pistons in two different engine. We measured the distance between the exhaust and intake reliefs on a stock piston and RIVA piston and there is about 80 thousandth difference between them.
    Holy shit!!!!!! Does anyone know where to buy a good brand bore scope that will fit through the 12mm plug openings. I need one asap to take a peak, man this is some major shit for Riva!!!

  7. #7
    800AMSOIL4U's Avatar
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    Quote Originally Posted by dnielsen View Post
    Holy shit!!!!!! Does anyone know where to buy a good brand bore scope that will fit through the 12mm plug openings. I need one asap to take a peak, man this is some major shit for Riva!!!
    http://www.greenhulk.net/forums/show...&highlight=9mm

  8. #8
    800AMSOIL4U's Avatar
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    Quote Originally Posted by dnielsen View Post
    Holy shit!!!!!! Does anyone know where to buy a good brand bore scope that will fit through the 12mm plug openings. I need one asap to take a peak, man this is some major shit for Riva!!!
    http://www.greenhulk.net/forums/show...&highlight=9mm

  9. #9
    Got Boost? psycho rxp's Avatar
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    JP, I noticed the same on my .20 over 8:4-1 Riva pistons last time I had the head off. I thought it was due to worn out valve guides, and my setup. So, I clearanced them, installed new guides, seals, and replaced all 6 BENT exhaust valves, with new ones. Also installed the Rotax cam chain tensioner, incase there was slop in my chain, from having the head surfaced/valve job too many times.

    Sounds like this isn't an isolated case now....

    Check your valves,& guides. How many times has it been surfaced?
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  10. #10
    Having Fun jp1300r's Avatar
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    One engine has had the head and block decked and the other one may have had its head cut alittle. The last one the cylinders were just honed out and pistons installed. They both appear to be hitting in the same place on both engines. There does seem to be plenty of clearance its just not in the right place.

    Jason so you clearanced your pistons? Did your piston look like the pictures I put up?

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