I'm considering using a set of KB920 pistons in a Buddys Evo.
He has a set of J&E +.030 pistons that have been in there for maybe 30k miles. The guy that bored the cylinders for the J&E's didn't use torque plates,
the distortion is clearly seen by the alternating polished and still showing crosshatch streaks down the bore.
I'm not sure if I could get the jugs torque plated and take a thou or 2 off to get them round and use the current J&E's or just bore to .040 and get new pistons.
The KB920 with a 8.5cc dome would put me right where I want to be for compression. The J&E's have been cut down already and still have 200 CCP with an EV-27 cam. I'd like to get the CCP down to about 185.

 

Years back there were some issues with the KB pistons but I wouldn't hesitate to use them at this time, I believe the ones you describe are a 4032 forging which can be setup at a fairly tight piston to wall clearance. The price is certainly attractive.

 

The price is not the main issue, Wiseco's are only about $20 more.
The Wiseco dome is 12.5cc and that puts me back to where the J&E's are.
With 200 ccp, the bike needs 94 fuel and that can't be had everywhere.

 

KB forged pistons are OK.streer clear of the hypertecnics though.junk a while ago.still junk now

 

What's you combustion chamber size?

 

Bone stock, 83cc

 

Thank you for the info.

 

Did a little static comp check and I know you said you wanted to knock down the comp a little. Just wanted to note, With the Wiseco piston 10.0:1 and a 12.9 cc dome you can still get your static down to 9.85 with a .045" head gasket and with the cam at 36* it'll put you right at 190 ccp. Just a thought...

I can understand the probability of detonation with that high of compression (200 ccp) with stock heads. That's a lot of heat build up in the motor. If you opened up the heads a bit and a good tune I bet the detonation would subside... I have no issues with 93 fuel...

 

The 12.9cc domed Wiseco's have a dome wall thickness that allows it to be modified, and still be well in the safe zone of .180".
That said, we have a hyperutectic set from years ago, if anyone is interested.
$75.00 takes them.
Scott

 

I need to make this work with 91 fuel. We can only get 94 in a few towns around here. the stations that used to have 92 have switched to 91.
I also wanted to get the squish down to about .032