96KX60 needs diagnostic help

[bbbom]

First race weekend of the season and my daughter's KX60 is giving me cause for concern.

She did MX school the weekend before last on her KX and it ran fine for the whole 8 hour class until the last 30 minutes. Had trouble getting it to fire up after she ran the first start & waited for the next group to go. Swapped out the plug which looked pretty black but not bad. Still wouldn't start so we push started it and she did the next starting gate drill. Bike died when she got back to the gate, couldn't get it to start again so pushed it to the truck since she was done and tired.

Karl cleaned the carb after we got home, looked like something clogging the pilot jet. Bike ran great around the house and on a short ride Sunday.

Back at the track this past weekend, bike ran good Saturday for 2 practices & 4 motos. Sunday ran good but she complained of it bogging in 2nd & 3rd when she backed off the throttle like entering a corner during practice. It was pretty cold out early in the day but warmed up to the 50's by midday but she still had to choke it each time to start it after is sat for like 5 minutes. She'd choke it, start it, shut off the choke, warm it up then clean it out and a good stream of blue smoke would come out of the pipe. It also sounded like it was missing as she went by when she was on the pipe.

Haven't had time to clean the bike up & start tearing into it but was curious if anyone could make a reasonable guess on where to start - carb? top end? bottom end? We don't do the top end very often as she just got interested in racing late last fall. She only has another month of racing this little bike because she really needs to go to an 85 but she wants to finish the series in the 60 class (not quite ready to race an 85).

 

[Martin Cole]

Hi - It sounds to me like if you've already had dirt clogging the carb jets that you need to flush the whole system. Perhaps there's some filth accumulated in the tank and it keeps getting through. Clean it all out and try again.
Another thing to watch for on the KX60 is under the tank where the coil bolts to the frame. The bracket can snap and cause intermittent or permanent end to sparks. If it is the problem - get it brazed back in place but beware of painting it afterwards. You must make sure the coil will earth out. A lot of people have trouble with this when they repaint the frame and rebuild the bike.
MC

 

[bbbom]

Thanks for the ideas Martin. We are doing a top end on it tonight since it's been quite awhile since we did it last and she's starting to really make the little bike work.

We'll be checking out the carb again to make sure the system is clear but I'm not worried about the bracket for the coil since the spark has seemed fine except for the one episode and that was more likely due to the pilot jet being clogged.

Next round of the series is a week & a half away - we'll get it dialed in before then I hope!

 

[Gazza2005au]

pull the tank off pour out the fuel than sit the tank out in the sun for a day to let the tank fully dry out u probebly have "water" on the bottom of your tank also replace your jets

 

[Jasle]

I'd agree with the cleaning out of the old fuel idea. clean the jets, you should be able to see throught them. Also thouroughly clean the carb body. dirt can suck in the bellmouth and get stuck in the pilot circuit. you need compressed air working backwards through the pilot jet area.
then when the bike is started and warm spray wd-40 or carb cleaner around the base of the cylinder and the seam where the case halves go together. see if the idle goes up or down when spraying. this will check for an air leak which can cause problems.
Also check your air box for crud. most people think dirt gets in the carb through the fuel but the petcock is typically screened. most crud comes in past the air cleaner vai a crack in the air box or simply getting through a too dirty air filter. This is how the pilot circuit can get clogged.

 

[bbbom]

Thanks for the tips!