Maintenance & Technical > KX500 Original

Surging

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maxfli11:
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.

reklessj:
U don't need it to idle. Alot of the surge will go away at least it did on my new motor but they all surge a bit

Foxx4Beaver:
The fuel leaking on the motor is most likely due to a worn out float needle valve and/or float valve seat. You can try replacing the float needle...what happens is the rubber tip gets worn, and no longer gives a good seal...same with the "seat" it rests in.
I went through this with mine for a few months, replacing float needles, only for it to be a temporary fix, because the seat was also badly played out, being the original carb. So I just opted to buy a brand new carb from Sudco...problem solved.
As for the surging...you want to get that leak fixed/figured out 1st....then get it jetted as precisely as you can(making sure the float height is set correctly first).
There's lots of threads on here concerning surging, most of them are old threads, but still very useful...do a search on surging and you'll find plenty. As rekklesj mentioned, you don't need it to idle...I myself don't have my bikes set to idle...I find it annoys me...but, you'll also find that in some of the surging threads, that some members found that setting the bike to NOT idle, actually helped reduce the surging considerably....whereas some members found no difference at all....so it could go either way for you, but worth a try.

Foxx4Beaver:
You never mentioned if you've done a leak down test to that motor either...that could be crucial to your surging issues "if" it has an air leak....somethin to think about.

maxfli11:
Yeah. I have no idea how to pull off an accurate leak down test, and I'm afraid of what it's going to tell me. I think everything in it is original. I really don't want to tear this thing completely down and go through every seal and bearing. Might be the right thing to do, but it's riding weather! The surge isn't a big deal. Just not used to seeing it. How do you test for leak down?

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