Turns over weird, runs for 100yds then dies

[BrewCityMusic]

Allright - after redoing all the electrical on my cart (an 88 Marathon 2PG) I have a whole NEW problem ... The cart ran fine for a couple of days, but now when I press the pedal, it sometimes acts like it can't quite decide which direction to start in (the flywheel turns back and forth about 10 degrees, then if I let off the pedal and press it again it'll turn in one direction and start normally).

Also, once it IS running, it will take off good, power is maybe just a hair off of where it was, but after about 100yds it will just die, period - until it completely stops. Then, if you press the pedal, it will fire right up again and run for about 15 seconds, backfire sometimes, sometimes not, then die again (frustrating as hell).

Is there a possibility that pulling and repairing (then pulling again and replacing) the pulsar with a new one has thrown the timing off or ? - I didn't adjust or move anything (like the ring that the pulsar mounts to), just unscrewed the old one and replaced it. If it IS a timing issue, could someone give me a pointer or two where to start getting this cart back to normal? Thanks!



ADDED 343PM: Just for grins, I pulled the carb and cleaned the jets, etc, also swapped out the solenoid (again) to no avail, even went from the HEI conversion I added back to the factory igniter, no help, same **** thing - gonna try and swap out the coil I guess, if that doesn't do it then I'm almost going to HAVE to assume it's a timing thing, aaaaargh

ADDED 430PM: Well, I swapped the coil, no change, plug wire too ... The new Pulsar ohms out at 178, but it's generating a little over a volt of AC so that's good.

[BrewCityMusic]

Well, I pulled the plug and it looked burned, actually pretty severely, so I replaced it and the cart ran, but chugged pretty good and didn't have a ton of power so I swapped back to the HEI and now it seems to be running OK (just "OK" though, it's not quitting or qanything but seems to have maybe 10-15% less power than it did before it started screwing up on me) - just gave it a 10 minute shakedown and it didn't stall ... I'm wondering if these crappy Autolite 725's are just a really bad match for the cart?

Now I just hope I didn't mess up the crank seals with all the backfiring that was going on, I'm scared about the slight loss of power *gulp*

[Dave Box]

Good Lord BCM that handsome little cart is surely giving you a bad time, I'm sorry to be reading your litany of woe. Not that it's any consolation to you but I am just putting my engine in for the second time. I got 4.5 hours out of it before a catastrophic failure.

I am using the EZGO recommended plug which is NGK B6S and that seems to be holding up fine. With regard to the timing I am ashamed to say in public that I never worked out how to adjust the timing on the fly. Clearly you can move the pulsar in its ring so I just set it in the middle and hoped. On the positive side I know that a 2 stroke is remarkably tolerant with regard to timing.
If you were / are getting a true backfire (as opposed to spitting back through the carb then you have unburnt fuel detonating in the exhaust pipe and that will have no effect on your crankshaft seals so I would not worry about that too much.
Good luck with it BCM keep us posted on your progress.
Dave

[BrewCityMusic]

Yeah, Dave - I've definitely had some undue "Fun" with the project, but the first couple of rounds I can't fault the cart on as they were due to inaccurate diagnostic decisions on MY part (probably something to do with this being my first "non-Harley" foray into engine work in like 20 years) ... Live and learn, I guess :)

I took several rides last night (between 5 and 15 minutes in duration) and so far so good, I'm having a really hard time figuring out in my head why the engine was turning over weird but the best I can figure is that I'm probably running at the fringe of too advanced, so occasionally it's popping before TDC, which is causing the engine to fire backwards against the starter - does that sound reasonable? Also, remember a week ago when I was having the "run-on" problem, well you were more than likely correct that there was a burr or ? that was glowing in the motor, probably on the plug (which was pretty burned, enough in fact to crack the resistor) ...

For now I'm going to cross my fingers and be happy that it's running good again, if there continues to be a gremlin with the timing then I'll mess with it just a tiny bit at a time until it runs right, on the upside that flywheel sure comes off nice and easy now !!!!

[BrewCityMusic]

OOOH - a new symptom, maybe this will help someone help me troubleshoot!

OK, so here's the deal, most of the time when I start driving the cart, it fires right up like it should and runs great right up to 4850rpm, plenty of power, etc. HOWEVER, sometimes it'll do that little "giddyup" I mentioned above before it starts, and when that happens the tach appears to be reading double the actual RPM's (meaning I can feel the cart running at about 2600-3000 max, but it's reading 5400-6000 on the tach) and when it does that, the cart won't go above about 3k, even at wide open throttle, has a lot less power, coughs and sputters, etc...

PLEASE tell me that this helps explain something, and if it does, could someone please explain it to ME ?!?!

Thanks again!