Bad coil or cdi?

[95formula847]

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.

[Purpletj]

Start here for the starting issues.
http://www.kxriders.com/forums/index.php/topic,2169.0.html

If you have a clymer it will give you the proper specs to test the CDI and coil. Also Im very curious. Have you done a compression test? what about crank seals?

[95formula847]

Start here for the starting issues.
http://www.kxriders.com/forums/index.php/topic,2169.0.html

If you have a clymer it will give you the proper specs to test the CDI and coil. Also Im very curious. Have you done a compression test? what about crank seals?

Ok, ill try and find my Clymer manual. I thought I looked though it with no luck but I may be wrong. Its got a bran new top end. I believe my last compression test was 3 rides ago and it was 140psi+ warm. It def has good compression as its not easy to kick.

The bottom end is still unchanged since the day I bought the bike. I do not lose any gear oil nor does it loose any coolant. Coult crank seals still be bad?

[Goat]

I have had the same kind of issue with previous bikes I have owned. Most of the time it was the coil. If it has a crack in it it will work fine until it gets hot. As I'm sure you know metal expands when it gets hot which causes a gap and the coil doesn't work as it should. Moisture can also get in there and make it short out. I've only had one cdi go bad (No spark at all) but that bike would never start until I replaced the cdi then it was fine.

As far as crank seals go. No coolant would leak as it doesn't go through the cases at all. The gear oil doesn't run through the crankshaft channel either. That is lubed by the fuel/oil mix that the engine runs on. Page 111 in the clymer manual shows the operating principals to help understand a little better. Also page 46 for pressure testing to make sure your seals are still ok or not. Any questions feel free to ask. Hope this helps.

[95formula847]

Great! Thanks a lot. Im looking through the manual right now!

[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]

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.

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?

[95formula847]

Ya I may send the motor to someone like Stewart and have it done for real. Bottom and top. Well see when its apart.

I rebuilt it myself.

[Friar-Tuck]

95,
  Good call On the pressure/vac test.  Not unusual that several things slowly start affecting your performance.
    If you do decide to send off your engine to Stewart-San or one of the other builders here they may also check out your electrical system.  The re-builders have several of just about everything and will be able to troubleshoot what's going on by swapping out verified operating items quickly.   
  Just a thought.
  Tuck\o/
 

[95formula847]

Well I may just replace the base gasket with a better one from Cometic. I had just the standard Cometic gasket on it but I am going to call them and ask about one i read about on here. A metal gasket surrounded by silicon or something like that.

Ill check the base of the jug and case surface for warped or uneven areas also. If it blows after that then ill have it checked for real. Id rather not put a lot of money in it right now if I don't have to.

[95formula847]

I pulled the top end off. Im a dumb dumb. I put the base gasket on upside down and the cutout for the power valve rod was on the wrong side so it pushed up through the gasket and bent/tore it.

How far does the rod go in and out? The gasket only bent in a quarter inch so the rod wasnt moving any further than that. Do you think I was losing any power because of this?

I ordered a new gasket from Cometic. Its a steel coated in some type of rubber. Guy there says it should work great.

[Goat]

It's possible that with the rod hitting the gasket the valves wouldn't open completely or at least create a little drag. You would only lose a little power on top end if it can't open all the way. Glad it's nothing major.

Don't feel bad everyone at some point puts a gasket on upside down. I sometimes forget the ring on the head gasket has a skinny side and a fat side and the fat side goes down. You just get excited and lose track of what you're doing. Just have to slow down and double check what you're doing sometimes.

The rod that opens and closes the valves only moves about half an inch.

If you could get a pic of the gasket when you get it that would be sweet. Also is it factory thickness or is it thicker/thinner? I've always used the fiber gaskets but the metal one has me interested.