I have had no problems with my 23 hp L/C Kawasaki in my Lazer Z until 2500 hrs. I just found out that the muffler started to breakup inside and fed metal into the valves. If you own one that has the muffler slightly elevated above the exhaust ports watch out for this around 2000 hrs. My muffler started blowing red puffs of rust when I went to full throttle. Anyway I'm replacing the valves, pushrods springs etc all because of the muffler. A piece of metal was stuck in one of the valves.