Maintenance & Technical > KX500 Original

Bad coil or cdi?

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Friar-Tuck:
 When you start going through all the system checks sometimes the simple things can make a difference also.
    Checking all the connections and cleaning them, corrosion,loose etc. make sure your grounds are clean and verify your plug wire,plug,cap and kill button/switch are good.   If the coil and cdi check out there's only one other electrical componant I can think of, Pull the flywheel cover and have a peek. There are connections on the stater plate that might need some TLC also.
Sorry if you've already tried this stuff. 
  The tough part is checking the coil and cdi when hot.
          I had a chainsaw repair with the same conditions and had to swap out the parts with working ones from someone elses saw.  I had to borrow the saw with the good parts 'cause just like Goat said it checked out to be in spec when cold.  After a few cuts it would die and wouldn't start again 'till it cooled off. 
  Tuck\o/

Polar-Bus:

--- Quote from: 95formula847 on April 06, 2010, 01:08:52 PM ---I just did a top end on my bike and added vfroce reeds, fmf powercore and pc pipe. I just got it back from the shop to get it jetted right and it seems to run fine other than not idling very long.

But, after I ride it for awhile and shut it off, its very hard to get runnin again. It takes me a good 10-15 min kicking it to get it to fire. Once its running it seems fine. But if i get stuck anywhere with mid or anything on my boots and it shuts off... im screwed. I cant kick it like crazy as the kickstart has no grip. But even so it wont start with any good kicks I get in.

So, im wondering if there is a way to test the coil or cdi with a meter and make sure im getting good spark? Does it not starting good when warm sound like anything in particular? I have read that once a KX500 is warm it should start in one good kick. That has never been the case for me.

Also, my starting method when cold is:
-turn on gas
-lean bike and wait for fuel drip
-put in 2nd gear
-rock back and forth a few times
-kick through slowly a few times with throttle open
-throttle a third open
-tdc kick the poo out of it

This usually doesnt work unless I keep kicking for 10 min.

Starting method when warm is just to kick it with the throttle open at tdc.

--- End quote ---

simple compression test cold vs. hot ?

Hillclimb#42:
The 500, especially with a new top end, can be hard to start with an old kicker and jetting being off just a little. I had an old kicker and it was making my boot slip off. As soon as its out of square with the bike its tough to keep your boot on it. That led to tearing up my boots and also getting cracked on the leg a few times. Also, mine has always needed me to open the throttle a little when warm, (all the way open after a wreck) no throttle when cold. Sounds like an air screw or pilot may be off adjustment or partially clogged, or Maybe you are going a little overkill on feeding it fuel during prep. I haven't seen too many people lean it over, rock it and hit the gas with a few easy kicks and then still cracking the throttle with the choke on. Try it without any of the prep.
  Try gas on, choke on, kick a few times easy, cycle to the compression spot, wind up the kicker to the highest spot, then drop the mojo on it. No throttle. It should start with a high idle, then calm down to a normal level, then thats when I turn off the choke.
  After warm, 1/3 to 1/2 throttle, also needs to be at TDC to get a full kick.
Electrical problems suck, I hope you get it figured out, good luck.

95formula847:
Well, I used an aircraft heater pressure tester to test the engine out and guess what?! Got a leak. A pretty big leak too. Its right below the exhaust on the front of the jug where the jug meets the case. So either the base gasket is bad or the case surface is not even there some how.

Do you guys think this could be my starting problem? Its not a small leak at all as it blew all the caked dirt off that apot when I turned the pressure up to 7 psi.

Any ideas?

Im gonna test the coil now.

Goat:
Definitely the problem or at least part of the problem. With it leaking like that it doesn't have sufficient vacuum to pull the fuel through the system.

If it's that bad I'm willing to bet it has sucked in enough dirt to destroy bearings and seals. Probably not what you wanted to hear. But it's a good possibility.

Did you have the shop rebuild it?

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