I'm running the KLX300 cylinder now and want to go to the Kustom-Kraft 331 kit but I worry about the durability of the bottom end of the motor. I'm looking for some insight and some data? How is your 330/331 holding up?

 

Put the Bill Blue 331 on in October last year, I've done 300km, but all on dirt in a dusty Australian summer. Runs great.

 

I have over 2000 miles on my 331 build. I'd hesitate to say that they were easy miles, too. I don't abuse the bike, but I sure don't baby it either. It runs like a scalded dog and so far, no strange noises. The bottom end is the same one Jerry Leighton with Four Stroke Works used for Larry Roeseler's bikes, only Jerry stroked the crank when he bored the jug. He tells me that they hold up fine, even at that level of performance. He ran carbs up to 39mm with the 365 too.

Maintenance and how you ride the bike will have more to do with longevity than the overbore.

Rock and roll and enjoy the ride.

Bill Dragoo
Norman, Oklahoma
KLX 331, Web Cams, Luke's Racing Head, Bill Blue TM 34, FMF Q4 W/Powerbomb header, BB SS brake lines, Clarke fuel tank, and so on...

 

Around 1,300 well abused miles. The upgrade made lots of low end noise the first few hundred miles when cold. But, now I don't have any concerns about reliability. I really runs very well on single track, at the 2000-3000 rpm range.

Torque is awsome.