Cylinder gouged twice after BBK install

[liftit]

I had a wrist pin clip come loose on my stock bore, so I went ahead and ordered a bbk to replace it with.

On the first install I ran a magnet around the crankcase to make sure no pieces of metal were hanging out in there. Nothing to be found. Installed the kit, started right up, made it about 20 feet and it went bang. Pulled it apart and there was a gouge down the side of the piston and a matching one down the side of the cylinder. Looked like it down when a wrist pin comes loose, but they hadn't and I couldn't find pieces of metal anywhere that could have done it.

Honed the cylinder, got a new piston and went to work again. Chamfered and smoothed out the ports more completely in case they had caught a ring or something. Even turned the engine on its face and spun the crank to see if anything fell out. Installed everything with great care. Spun the crank to make sure everything moved smoothly. It looked and felt perfect. Started it right up again, went to turn around and go on a test run and it went bang again. Another gouge about a half inch away from the first. :banghead:

Anyone have any ideas? I can't find a burr or loose bit of metal anywhere that might cause this and no clips are missing.

[90GTVert]

That sucks. Have you tried rattling the pipe around to see if anything comes out of it? Maybe try flushing the engine case out with kerosene or something?

[jmkjr72]

are you still running the stamped steel reeds

if yes i would take a look at them to make sure you didnt cunk a reed they dont like the higher rpms

[jmkjr72]

another thing i thought of you did replace the wrist pin bearing right

[liftit]

brand new bearing.

[190mech]

You may have a piece of clip wandering around in the crank area and is getting up into the cylinder thru the transfers..Anytime I have a failure like that the engine gets turned cylinder down and washed out with a garden sprayer filled with mineral spirits,the crap then falls out with the solvent..Also as Brent said,check the pipe closely too..

[liftit]

I turned it cylinder down, but I didn't spray it with anything. I may have to do that. Thanks guys.
Sucks riding a bike back and forth to work while this thing keeps giving me headaches