KDXRIDER.NET

Hey y'all. I've got a neighbor who's a powersports mechanic from home these days and he rebuilt my KDX from the crank up for me. Runs good but it's got a whine and I'm not sure what it is yet. Haven't tried isolating it with a stethoscope or wood handle or anything just yet but I wanted to post a clip and get some opinions. He said he replaced the water pump because it felt notchy but the whine has persisted. May be something minor. I hope. Bike might need some carb and/or clutch adjustment but is running okay overall.



I've done some reading on different whining noises in KDX's and I've read about different culprits, and some say it's normal but I've heard other examples that don't have this noise. Any advice is appreciated.

Wow, that's pretty loud. I assume the bike ran fine without the whine before the rebuild?
If so, something has been rebuilt incorrectly / some aftermarket part is just a slightly different spec than OEM if OEM parts weren't used if I had to guess. I'd be hesitant to run a bike with a whine that's so loud if it wasn't there before the rebuild.
OEM crank bearings or aftermarket? OEM Crank?
What trans oil are you using?
One more thing, how much time do you have on it since the rebuild?

At the same time, I don't own an H series, so I'm just giving some general guesses, but I'd start seeing what parts are in the bottom end.

Best of luck.

I hope he relieved the side load on the crank bearings, like you say a stethoscope will be your best option to diagnose
My bike has a slight whine even after a full rebuild but I think it's coming from the water pump as that's the only thing I didn't rebuild

I think the bearings are OEM, crank was rebuilt. Water pump was replaced. Not sure on the trans oil but I will probably change it soon so I'm open to recommendations. Only a few minutes of seat time on it but my mechanic buddy said he couldn't find anything else wrong after replacing the water pump. I don't think the noise was present before the rebuild, but before it was mostly power valve or rod noise. Tapped pretty bad. Not sure if fuel was bad but ended up holing the piston early on after getting the bike.

I've read this could be water pump, clutch, or kickstart gear related as well so I'm trying to figure out what to be looking for there if I pull some things to inspect. I'm not really set up to split cases with my little shed so I may go get a second opinion from another local shop.

Well a little concerning and maybe the culprit: very low transmission oil. Not even on the sight glass until the bike was leaned way over. Probably not for a wet clutch either I'll bet. Gonna grab a quart or two and change it. Might help.

assquatch20 wrote: 10:52 pm Nov 29 2025 Well a little concerning and maybe the culprit: very low transmission oil. Not even on the sight glass until the bike was leaned way over. Probably not for a wet clutch either I'll bet. Gonna grab a quart or two and change it. Might help.

I could definitely see that being the culprit. Luckily you said you didn't put much time on it since it's been rebuilt. Hopefully it fixes it and no damage was caused! It'll likely be nothing to worry about though.