I bought a '92 KX125 a little over a year ago and have never been happy with it's low rpm performance. It doesn't sputter, bog, or surge. It just doesn't have the "pull" that every other bike I've ridden has. I guess the best description I can give is that it can't pop a wheelie from a dead start in first gear. Maybe not the best description, but I can get on my son's KX65 and pop one. I can get on a friend's KTM 200 EXC and pop one. Any other bike, any other size, they all have more low end torque than my bike.
Just so I don't start a new thread on the much covered jetting saga, let's just assume my jetting is correct (not saying it is, but let's just remove that variable from this discussion). I've rejetted, repacked, replugged more times than I care to recall with minimal benefit to my low end.
I bought the bike with a FMF Fatty Gold series pipe and Powercore silencer. The pipe had a heafty dent in it, so I traded it out for a used Pro Circuit Works pipe that I got for dirt cheap. End result was again, very little improvement to the low end.
Installed Boyesen dual stage reeds and rejetted - very little improvement.
Fixed dragging brakes - lots of improvement, but still way short of other bikes.
Dropped the front sprocket from 12 tooth stock to 11 tooth - more improvement, but still not there.
I haven't ridden another '92 KX125, so I don't know if this is as good as it gets, but I'm hoping not.
The bike's manual states that one of the possible reasons for poor acceleration could be ignition timing incorrect or a fault ignition component. I'm not sure if I have poor acceleration, though. The bike climbs up the rpm range smoothly, just lacks power in the lower band.
Not sure where to look next, but I'm wondering if I need to start working on the top end now. Could a worn piston ring be the cause? I also read somewhere that a worn crank bearing could cause low rpm problems. Possibly the KIPS?
Any ideas would be great. Money is always an issue, so I haven't done a compression test yet or bought any tools to split the case, but if I get enough feedback that that's where I need to go next, I'm willing to.
Thanks.
Just so I don't start a new thread on the much covered jetting saga, let's just assume my jetting is correct (not saying it is, but let's just remove that variable from this discussion). I've rejetted, repacked, replugged more times than I care to recall with minimal benefit to my low end.
I bought the bike with a FMF Fatty Gold series pipe and Powercore silencer. The pipe had a heafty dent in it, so I traded it out for a used Pro Circuit Works pipe that I got for dirt cheap. End result was again, very little improvement to the low end.
Installed Boyesen dual stage reeds and rejetted - very little improvement.
Fixed dragging brakes - lots of improvement, but still way short of other bikes.
Dropped the front sprocket from 12 tooth stock to 11 tooth - more improvement, but still not there.
I haven't ridden another '92 KX125, so I don't know if this is as good as it gets, but I'm hoping not.
The bike's manual states that one of the possible reasons for poor acceleration could be ignition timing incorrect or a fault ignition component. I'm not sure if I have poor acceleration, though. The bike climbs up the rpm range smoothly, just lacks power in the lower band.
Not sure where to look next, but I'm wondering if I need to start working on the top end now. Could a worn piston ring be the cause? I also read somewhere that a worn crank bearing could cause low rpm problems. Possibly the KIPS?
Any ideas would be great. Money is always an issue, so I haven't done a compression test yet or bought any tools to split the case, but if I get enough feedback that that's where I need to go next, I'm willing to.
Thanks.