Bad news KA100 is a shocking motor. I seized mine over the weekend which was totally unexpected, the previous race the engine was running great, I’ve just changed chassis and finally had the thing dialed back in to my best lap times, then nothing.
Everything was spot on, jets, tuning, oil mix. So definitely the engines fault.
It only had 30 hrs on it!
I had never changed the ring, piston, or done anything other than clean it and change the carburetor diaphragms and spark plug.
It was a little amusing actually, I was at a club day here in Aus, and all the other competitors were coming up sympathizing about the fact it had seized, but really 30 hrs between rebuilds - I cant be to unhappy. And it has only picked up the ring, I should be able to just give it a clean up and away it will go again.
For sure, if you are wanting to be at the pointy end of the field at any regional or state level event you should change the piston and ring at way less hours than that (around 8-10 I’ve heard). But I’m not, I’m racing for fun and as a goal to loose weight, and if it had lost any power, I couldn’t pick it up from my lap times.
It has been a great investment, all the top guys in my class are all with in a few tenths, which is down to driver and setup not differences in engine parity. AND you don’t have to push start the thing like with the old Yamaha’s!!