In need of some expert engine troubleshooting advice

[kevinmacc]

I'm experienced enough with engine troubleshooting repair to get me into problem, but this one has me stumped, and would very much appreciate any input...

Had our Kitty cat for a couple years, always ran fine. This year, pulled out of storage and she fired right up. Kids drove it for 5-10 minutes and then it died. I have not gotten it to start up since. The engine won't fire at all. Engine turns over fine, but just no combustion (exactly like cranking with the ignition switch OFF).

Fuel - Carb appear to be working well, and just to be sure I've went throught it twice. All jets/orfices clean, float valve seals well and float height good. Gas is getting to cylinder. Have dried out cylinder/plug and started over in case of flooding, but still nothing. After adding a little gas to cylinder, it will fire maybe twice with a very small, wimpy pop but nothing like it or any other 2-stroke should, and them nothing again.
Spark - Used old and new spark plugs, and have checked spark visually and always good consistent spark.
Electrical - Have disconnected the wiring harness to be sure it is not any of the electrical switches, but some result.
Cylinder - Good compression (120psi). Exhaust/muffler is not blocked, intake and exhaust gaskets fine. Pulled head off, cylinder and head good with no cracks, ports clean, rings look good.

Compression good, fuel is there, spark is present, but no combustion in the cylinder. I'm left with something like perhaps the ignition timing system has went south somewhere, firing at the wrong time. Checked the flywheel timing mark, and it is right where it should be according to repair manual. My experience with the electronic ignition is that either they work well or not at all, but it should not fire at the wrong time?

Again, any help would be much appreciated. Thanks

[72]

The plug wire could be dumping to ground, when you test for spark the plug wire is usually in a different position than when attached to an installed plug. Crank it over in the dark and see if you can see any arcing. Have you pulled the flywheel off yet?

[pjba1]

I have a 77 that is doing the same exact thing. I am not an expert mechanic, but I generally hold my own, but this one has me stumped. Kevinmacc, If you get anywhere with this, please post and I will if I get anywhere. My 5 year old grandson is chomping at the bit and doesn't understand why Papa cant fix it. Hate to let him down! Thanks

[kevinmacc]

Thanks 72 for the advice. No luck finding any shorts in the plug wire.

With nothing else to check, looked up specs for the electrical system ('95 model) and checked all resistances. Secondary coil/plug wire was fine. But the external primary coil resistance varied from 2-4M ohms, where spec is only 11K ohms. Even though the whole system was still giving good spark, could the CDI just be delivering spark at the wrong time!?!?

Great to finally find something wrong, but sucks that it has to be one of the most expensive replacement parts. OEM price is $187, and found someone in MI selling new ones for $150. With no other options, guess I need to start replacing suspect electical components even though not sure if it really is the problem.

[99 kittys]

I've only been tinkering with these kittys for a little bit but I used to race quads years ago and I can remember having to replace a stator that was acting up on on off. From what I can remember it had weak spark and ran crappy. It was on a twin cylinder yamaha banshee so I think it ran mostly on one cylinder. Maybe your just getting too weak of a spark? From what I've seen on quads or snowmobiles CDI's work or they don't. Not sure how to check it but I'd look into the stator before buying a CDI.
Good Luck.

[kevinmacc]

Yes, I agree that CDI's usually either work or don't work. Any idea how to check a stator, without simply replacing it? I'm sure some shops have some special equipment to check them, but no idea how or who can do this outside of simple resistance measurements, checking for open circuits. And would one need to have the motor running to check stator? Mines dead.

Thanks for the time.

[kidsperformance]

I just have a few basic ?'s Is it fresh fuel? and if it is are you using 87 pump gas....may be a enthaol(sp) issue...Have you in the past running it with the governor bypassed?? Check the lower rod bearing..* all the yrs of working on these engines the cdi has been bullet proof and have never heard of a problem. I think that ign fires twice per revalotion. Pull the fan cover off and spin the flywheel with the spark plug out and make sure it doesn't roll like a egg(like a eccentric) if that's the case the crank is out of index

[72]

Just another shot in the dark......... if the flywheel does turn true, spin the engine with a drill motor (plug out)around 500 rpms and see how consistent your spark is. If that checks out ok then put a timing light on it and see if its timing is jumping around. The only CDI issues I ever had (that were not a complete unit failure), was related to cracked insulation that opened up with heat. The bike would run great untill it warmed up then break up for a second then shut down. Its frustrating, I know.

[kevinmacc]

For anyone experiencing simialr problems, I ended up purchasing another Kittycat and swapping out parts to find the problem part. Cheaper and quicker then buying parts that may or may not fix the problem. Found primary coil was bad. Don't know why, as resistance checks were good, but engine ran with different primary, but not with original. Always had good strong spark with bad and good coil.

Very strange, but at least some resolution to the problem.