I picked up my sons 05 250F new last september. It's been through 20 races or 40 heats, 20 pre race practices and lots of practice time this year. All races were in the begginner class and the bike got him a first overall in his class. He is pretty happy for his first year racing. He will start C-class next year.
I use kawi brand 10-40 oil non-synthetic. We change the oil after every race and the oil filter every other race. The bike is completely stock besides an aftermarket chain and uni filter. Anybody who owns one will know the stock chain is junk an never stops stretching. The stock handlebars are flimsy, but even after all the wrecks he has had, they have made it the whole season. I plan on getting some aftermarket bars for next year. The stock air filter just wore out quickly from cleaning and I like uni filters. Even switching to the uni the jetting has been spot on. I could have probably tweaked the jetting a little on a couple of our 100+ degree race days, but didn't. We've been cleaning the air filter after every race. I've always been a dunlop man, but the bridgestone tires that came on the kawi have worn like iron. In hindsight I probably should have replaced the rear with 4 or 5 races left, but made it the whole season on the one tire. I will be putting another bridgestone tire on.
We first checked the valves after 10 to 12 hours and had to reshim all four valves. I also lost a shim. We pulled the motor and washed it out with solvent, ran a magnet in and over every nook and cranny and never found it. Another 6 or 8 races later I took it to our local shop to have them check the valve clearance (I was pressed for time or I would have done it myself). When they pulled the valve cover they found my missing shim. Who knows where that damn thing was hiding at. It had been bouncing around on the exhaust cam and the cam was chipped up pretty good so we replaced it. The valve clearance was still spot on.
Another 4 or 5 races later the intake cam seized up during practice. The shop tightened up the cam journals by the manual and hadn't gotten the service bulletin about over tightening the journals. The owner of the shop is a good friend, our sons race together, we ride to the races together and he takes good care of me on parts. By this time we only had 4 races left and I was really hoping to get through these before doing a total rebuild. He plasti-gauged the journals and seized cam and was able to hand lap the journals and cam back to spec.
The bike ran good the first race after the seized cam was fixed. It didn't have much compression the second race and we had to push start it both heats. I checked the valve clearance and the left intake was so tight I couldn't get any feeler gauge in at all. I shimmed it back up hoping for the best for our last 2 races. The bike started up fine and ran good for the last 2 races. After the last race the compression was gone again. Opened her up and the left intake was tight again. The exhaust side is still in spec.
I'm not gonna push my luck any further. I was planning on a total rebuild this winter anyway and I'm pretty happy we managed to get through the whole season and only had to buy an exhaust cam.
I plan on getting a new head and going the kibblewhite route. What have you guys been doing on new pistons? Are you just checking the cylinder and if it is in spec just putting a new piston in? Anybody replating their cylinder or just buying a new one? Anybody had any problems with the bottom end or are you just rebuilding the top?
Overall I've been really happy with this bike and I will buy an 07 when they come out. I think I've taken pretty good care of this bike and I'm looking forward to another season on it. I do think there is a problem with the left intake valve and it will probably be just a matter of time before it pops up for everybody. Keep a close eye on the valves and just plan on replacing them as part of your maintenance and you should be good to go.