08-17-2013, 06:45 PM #1
- Join Date
- May 2010
- Brownstown Michigan
Anyone else ever have a Riva Gas Operated Power Valve grab a piston?
Hello GPR JEDI's. Any help would be greatly appreciated by me and my bank account! My ski was running so well after the last rebuild, I am so bummed out! I was told to leave Thirty Thousands clearance between the piston and the valve when it is all the way down. Did the piston and or valve expand while hot and cause this collision or should I have left more clearance during assembly? I have had problems with this motor for 13 years either breaking off RIVA billet powervalves or grabbing cylinders (4 different cylinders in 13 years) so last year I bought the Gas Operated ones from RIVA and now 2 months of use, later, (way under 15 hours of use), another powervalve grabbing a piston again!? I thought this was almost impossible if you went with the RIVA made Gas Operated Valves, that is why I paid $800 for them. Do I need to send out the 2 dinged up heads with the Jug to get redone by Millinium or does just taking off the "high spots" from the dings in the heads (the other head looks much worst from last years rebuild when the "regular replacement RIVA valve" broke in half last summer after catching the piston. Any chance this is something else coming loose from inside the crankcase (reed screw?, etc.? ) and coming into the cylinder banging around and then going out the exhaust port and just "scratching or nicking" the powervalve on the way out? There is barely a scratch on the powervalve, just seems like it would have done more damage to the powervalve (like in the past) than this little nick on the valve? Any chance I am using the wrong piston ring end gap that might have caused this? Thanks for the help from anyone who knows how to help me keep an engine together for more than one summer, Steven Jones.
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