What am I missing here ?!?!

[simple man]

I had an outboard do this and it was the coil. It " looked " like it had plenty of fire too! I put a spark tester ( the kind that looks like a spark plug with no ground electrode, no threads, and an alligator clip on its shell ) on it and found that the spark became very irregular under a load. I clipped the tester to each spark plug in turn and drove the boat with the cover off so I could see the spark. New coil = new engine! The thing ran great after that!
I know it will be difficult for you to drive the cart to test this way, so I'm going to suggest what I would do if it was my cart. I would put a good tow strap to a solid point on the rear of the cart and put the other end around a tree. If you have some damp grass for the cart to run on, I think you could load the engine enough and watch the spark tester and see if this is your issue. Under compression, you need much more voltage to arc across the spark plug gap than you do with it at atmospheric pressure. Good Luck, and I hope this does it for you!

[sockethead]

Do you have another carb you can swap out to test?
I had carbs that I've cleaned over and over again with no change. Once I replaced them, the motors ran great...

[BrewCityMusic]

Thanks for the ideas, guys - I spent my free time redoing my driven clutch tonight, but will try both the coil and the carb swap next ... like I said, almost everything else has been totally gone through and seems OK, I'll keep everyone posted !!!

[rljgaj]

I joined here yesterday and I'm having similar problems with a 2000 TXT 4 cycle I have found that the cylinder next to the clutch isn't firing / dead under load. In nutreal it will open up playing with the throttle but under load it want hardly go, in reverse it go ok but not great. Now I need to see why the one cylinnder isn't firing. Plug fires when removed and grounded.

[StoveBolt]

Originally Posted by BrewCityMusic

But I *still* can't get this thing to run up to RPM's like it should. It starts like a champ, and starts to wind up but then just sputters a bit at maybe 2k and seems to not want to go any higher unless it's not under load ?

Sounds like the governor, will it rev in neutral?

[sassycat]

brew,could it need more gas? lil bigger jet? i been playin with a 420cc clone and could only get 3800 w/no gov..then just recently i opened the idle jet very lil".013 or so total" and it changed,,faster take off,idles perfect and gets to 4500 but havent takein it over that yet..

[ryanjap33]

After about a year of trial an error I finally got my 1988 running again. Turns out it was the pulser coil. It was doing the same thing as yours, it would idle and start to rev then cut out and back fire.

I ended up replacing the pulser coil and it still did the same thing. In the end, I found out that the red and blue wires that go from ignition to pulser had an area where the wire was mashed. When the engine would start to rev and the circuit would short out and cut out my spark thus preventing the engine from reving more and leaving fuel in the chamber causing the backfire once rpm's dropped.

I replaced the red and blue wires and plug and my cart is running now.

Maybe check the continuity through the wires to your pulser.