I have a little Kawi Z125 Pro. Works like a champ as a pit bike and on the street but sometimes I take it on the go kart track. On the track, it works perfect for about 4-5 laps or so but when it gets really warmed up it starts to pop out of gear, usually out of second gear. It happens most after I downshift from 3rd to 2nd. It goes into 2nd, I can feel the engine braking, then suddenly it drops out of gear into neutral. As it gets even more warmed up it gets more frequent and then it will also occasionally even drop from 3rd to 2nd on the straightaway while accelerating. By the end of a 15-20 minute ride session it will fall out of 2nd about half the time, after a downshift; blipping to match revs makes it worse, and being in lower rpm range makes it worse; it does better if I downshift higher in the rpm range with no blip so there is more backpressure on it. After it cools down between sessions, it shifts reliably again for the first 4-5 laps of the next session. On the 3rd to 2nd downshifts it never goes straight from 3rd to neutral, it clicks into 2nd , stays there briefly, then drops out and goes to neutral. I pull in the clutch and upshift one gear, sometimes I get 2nd and sometimes I get 3rd. Other riders on this bike have the same issue, but again ONLY later in a ride session when the bike is ridden hard and well warmed up. I don't have this issue with any other motorcycles, I don't think it is sloppy shifting technique. I put different rearsets on with better components than stock (stronger shift lever) but it didn't help. I've been researching this and I guess these bikes often have shifting issues, there are suggestions to tighten the motor mounts, change the oil, and upgrade or adjust the shift lever (did that one already). So here is my question: if I change the oil in it to try to improve this situation, what oil should I use? Does the fact that it happens more when hot indicate a certain type of oil that would be better? Any other suggestions for fixing it? (I don't want to get into undercutting gears or anything really involved just for this little bike, it is not my race bike.)
what oil are you using now? what's the weight? maybe, based on your symptoms a thicker viscosity oil would help with the gear box slipping.
No, I have seen links to that brace but it seems to be out of stock everywhere. I changed the rearsets to the Woodcraft GP shift kit. The mechanism is great and the shift lever has a good solid feel, I thought it would help but it didn't seem to make any difference, it still shifts great when cold but falls out of gear when hot, no difference in shift performance from the stock rearsets.
