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new 9mm stroker crank knocking

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85 xr 100 with powroll stroker knocking on bottom end under a load when getting on the gas. has anybody else had this problem or is that how they sound? bottom end almost sounds like the rod is loose. thanks for reading.

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Might be that it's detonating the crank does increase compression. Are you using race gas? you might need an extra base gasket or something.

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i have a weisco 120 kit in it, had to shave piston skirt,bbr exhust, aftermarket cam, valves ,springs, not running race gas. noise is coming from bottom for sure.

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Like minifig-phil was wondering detonation.....? Any idea what you have for compression with this combination? Can we assume you very carefully made ALL the checks as per Powroll's stroker installation instructions? And checks for the cam and valve springs also? Piston cylinder clearance is correct? Lots of things to keep a eye on with these mods.:applause: Any of the Powroll stroker motors I've been around didn't have a inherent bottom end knock. Could be any number of things causing this.

Old School Al

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weisco piston chart shows i am at 12-1 compression, dont know if that changes with the 9mm stroker. i have not tryied race gas yet, cant really see how that will stop knocking, but worth a try. i will hook up my chasis ear tommoro and find out exactly were knocking is coming from.

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You bet stroking changes it, it also increases swept volume. Now with the larger bore will increase it even more. Think of it this way, you have more volume with larger bore, and now also longer stroke, and are compressing it into the orignal size combustion chamber. More volume compressed down to original size combustion chamber means higher compression. Guess you may have 13.1 or better.....? High compression needs VERY stable burning fuel (race gas) to prevent detonation. Trick ign with knock sensor is nice also to adj timing, but not a option here. Heavy detonation is REALLY bad on a engine .......... breaks pistons etc, etc, etc !!!:applause: Too much compression can make one.............:applause: and :lol: !

Old School Al

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Here are a few options for you to lower the compression. Get a copper head gasket from engines only. I don't know the exact measurment but it's way thicker than stock or Wiseco. Plus, it lasts a lifetime. Just heat it up until changes into about 10 colors and dump it in water and your good to go again. Another thing is run two base gaskets. You will have to calculate everything out to get the exact compression ratio you desire, but we always used copper head gaskets and I've never have an issue with two base gaskets.

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also you can request whatever base gasket thickness you want from comedic if you'd rather not double them up.

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What Dave Miller used to do was cut the cylinder to provide what the correct compression we wanted. Since the copper head gasket is thinker, he would cut the cylinder a distance between that and a stock gasket. He had all the measurements written down or in his head, but you can measure everything. I calculated your compression ratio and I came up with 14.2:1. So if you're no running race gas . . . yikes. I based my calculation upon using Wiseco gaskets and ending up with 12:1.

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I Ran 106 Or 104 Race Gas Today. Still Knocking When Cold Or Hot. I Hooked Up The Chassis Ear, Noise Coming From Cylinder. Probably Just Going To Rip It Apart And Recheck The Play In The Rod. Thanks For All The Ideas And Your Time.

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