Strange Engine Problem

[nd jat]

The coil is basicly a step up transformer, heard of tesla coil? I believe if I'm right there should be a resistance from the wire windings on both legs (shorter being less resistance the longer having more resistance). Longer the wire the more resistance, like a garden hose and water (longer hose more resistance to the water flow).

Ignition primary coil reads at 0.0 ohms, occasionally jumps up to 1, then right back to zero,

would indecate a short. Hope this helps you out.

 

[pricetc3]

if it were me it would be a good starting point to replace them and could be the end of a headache i thought i had a coil prob and so i took my buddies off and put it on mine and it did nothing so if you got a buddy with a blaster bring it to youre place and swap parts to trouble shoot then there wont be any out of pocket for the wrong part

 

[PMitchell08]

Well I found a local blaster aficionado who knows his way around a busted blaster pretty well. Told him about my problem, we did plenty of troubleshooting and are both convinced that there is plenty of spark, thus the electrical system is a non-issue.

Although my compression tester read as being well within spec, we decided to tear into the top end anyway, seeing as it is the only thing I haven't had apart. It doesn't look bad but there is some blowby at the rings, a few small marks on the piston, nothing deep though, and the fuel on the walls of the jug appears to be too thin, possibly not getting enough oil. So we've decided that although it is nothing terrible compared to most blasters, it may be just enough wear to keep it from running, so we've decided to do a top-end rebuild. My conclusion as of right now is only that my cheap off brand compression tester is an absolute POS, and probably read much higher than what the compression was really at. We'll see what happens when I'm finished with the top end at the end of this week.

I apologize for wasting your time with a phantom issue, don't hold it against me, hold it against poor quality tools. If nothing else, I've learned not to cheap out on my diagnostics.

Thanks everybody.

 

[PMitchell08]

Interesting developments in this mystery diagnosis. Did a fresh top end, new rings, piston, bearings, bored .05 over, got it all back together, still doesn't start.

Tore it all down again, took the flywheel off to check the key, crank seals are leaking slightly. Replace seals on both sides, still won't start.

On a hunch decided to swap the stator for a different one, fired up on the first kick.

So my theory is:

Had good compression, had spark, had fuel. Crank seal went bad but it still ran fine. With each stroke of the piston a little dust is brought in through the leaking seal, and a small amount of corrosive exhaust buildup is pushed out of the seal. Ran fine when I put it away, but that thin corrosive material sat on the coil all winter long, through many temperature changes. There was nothing visible to suggest serious damage, but enough to cause a bad connection or a short in the coil, still allowing some spark, but the change in resistance may have altered the timing or weakened the still visible spark.

So although it didn't absolutely need a top end or a carb rebuild, it was going to be due for one soon enough, just good maintenance to get all that out of the way now I suppose. Anyway she runs great now and I'll be on my way out to Perry State Forest (Central Ohio) early tomorrow morning to break her and and seat up those fresh rings. Thanks again everyone. I need to go apologize to my cheap compression tester, it probably wasn't as far off as I had thought.

 

[Luni]

When testing primary and secondary coils on the ignition, you have to change your range of testing. Your DMM will have different ranges to test with.

One of them tests at teh 1-10 range. The other one tests at teh 100 range.

Ignition Ohm Test:

primary x 1 - 10
black and orange
1.44 - 1.75

secondary x 100
Orange and spark plug lead
5.28 - 7.92

Edit - glad you got it. Your issue was my issue. Exact same damn problem. Swapped in a stator and BAM fired up first kick.

 

[stephen12091985]

see if your woodruff key is sheard

 

[PMitchell08]

Thanks Luni, yeah my DMM is auto-ranging so it took care of that for me. For whatever reason the primary ignition coil tested bad but it works fine, someone else on here said their coil tested bad when it was actually fine as well. Regardless its been a hell of a time trying to diagnose this thing, but no worries now, I'm goin' ridin' tomorrow!