Maintenance & Technical > KX500 Original
Surging
maxfli11:
--- Quote from: Foxx4Beaver on April 03, 2019, 10:19:55 AM ---
--- Quote from: maxfli11 on April 03, 2019, 10:02:43 AM ---Sweet! Thanks!
--- End quote ---
Just so you're aware, the reason I suggest doing a leak test...is because "IF" you do have an air leak, it'll be impossible to jet it....you'll be just going in circles. This is a case of better safe than sorry.
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Well I don't want to get caught in a lean situation and seize either. The previous owner did seize it. It's bored .5mm over and nicsill plated i believe. I don't have a warm and fuzzy about it.
Foxx4Beaver:
Alot of times surging can mean it's getting extremely hot, and ready to seize...not always, but sometimes. I had a CR125 do that to me once years ago...and just a couple years ago my sled did the same thing...the mag side crank seal went whilst I was out riding, and by the time I knew it, it was too late.
Polar-Bus:
--- Quote from: maxfli11 on April 03, 2019, 12:27:09 AM ---Got the beast out yesterday for it's first breakin ride, and after a short fairly fast run it wants to surge two or three times before it comes down off the pipe. Keep in mind this is the first time I've really ridden this bike since i got it, rebuilt it and broke it in. I've read some of the posts on carb tuning, and I haven't checked plugs or anything yet. I did notice this morning that a little fuel had leaked out of the carb from somewhere onto the crank case. I'll find that tomorrow. Just need a good starting point to get her tuned up. She idles like a new one, and mid range seems good. Not sure about top end, I haven't got anywhere i can open it up like that where I'm at. I wouldn't bet I got it out of third gear. Wasn't counting.
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What were the ambient temps when you ran your bike ? Do you know what the current jetting is ? All KX500's do have a small amount of "decell surging". It's just the nature of the engine. If you have a sound fresh top end there is no way you can sieze a fresh engine from just light acceleration as you described. Like Foxx commented it is possible you have an air leak. You can check for a mag side crank seal leak by removing the mag cover, start the engine and spray some carb cleaner behind the flywheel, if you hear an abrupt change in engine rpm you have a bad mag side crank seal. Another tell tale sign of a bad PTO side crank seal is if the engine uses a lot of trans fluid, but you have no external leaks. The crankcase pulses suck trans oil through the seal and burn off your trans fluid.
maxfli11:
--- Quote from: Polar-Bus on April 04, 2019, 12:35:48 PM ---
--- Quote from: maxfli11 on April 03, 2019, 12:27:09 AM ---Got the beast out yesterday for it's first breakin ride, and after a short fairly fast run it wants to surge two or three times before it comes down off the pipe. Keep in mind this is the first time I've really ridden this bike since i got it, rebuilt it and broke it in. I've read some of the posts on carb tuning, and I haven't checked plugs or anything yet. I did notice this morning that a little fuel had leaked out of the carb from somewhere onto the crank case. I'll find that tomorrow. Just need a good starting point to get her tuned up. She idles like a new one, and mid range seems good. Not sure about top end, I haven't got anywhere i can open it up like that where I'm at. I wouldn't bet I got it out of third gear. Wasn't counting.
--- End quote ---
What were the ambient temps when you ran your bike ? Do you know what the current jetting is ? All KX500's do have a small amount of "decell surging". It's just the nature of the engine. If you have a sound fresh top end there is no way you can sieze a fresh engine from just light acceleration as you described. Like Foxx commented it is possible you have an air leak. You can check for a mag side crank seal leak by removing the mag cover, start the engine and spray some carb cleaner behind the flywheel, if you hear an abrupt change in engine rpm you have a bad mag side crank seal. Another tell tale sign of a bad PTO side crank seal is if the engine uses a lot of trans fluid, but you have no external leaks. The crankcase pulses suck trans oil through the seal and burn off your trans fluid.
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So i think i found an air leak source. My fault. The intake clamp was left loose after i installed the subframe last, and it was not over the intake completely. :( found the fuel leak also. The overflow tube had come off and was missing, a well as some fuel coming from the bad connection on the intake boot. All sealed up now. Ready for next shake down ride. Still looking for a slight antifreeze leak. Had some antifreeze on the cylinder on top of the kips valve linkage cover. Noticed possibly some moisture around the head gasket. I checked all torque and they were fine. I did dump it over on that side while i was riding, so it may be from that and the radiator over flow. I hope!
Foxx4Beaver:
Glad ya got it figured out...but it sounds like you should really take some, and go over that thing completely, to be sure you don't have any more unpleasant surprises, that could potentially end your riding season temporarily. :wink:
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