An interesting intermittent loss of spark problem

[Fairtax4me]

Had a fun one earlier today.
The health center staff called to say one of their carts quit running and they could get it to start but it wouldn't go. They were spot on, it would start and as soon as the clutch started to grab it would sputter and stumble and die. It wouldn't make any power to go up the hill from the health center. I eventually managed to baby it up the hill after running it in service mode until it warmed up some.

Back at the shop I checked it for spark, it was there but not real strong.
Changed the spark plug even though it was changed in about 2 months ago, tested the rev limiter. This one is a 96 so I checked to see if it has a separate igniter, and it does not.

Ran it in the shop and the sputtering and rough running continues.
Before I gave it to them last week I had done an oil change, fuel filters, and a valve adjustment. So I re-checked the valve adjustment just in case, and it was fine. Also checked the filters really close for water. I just power washed it a few days ago, maybe a bit of water got in the tank. I don't see anything obvious in the filters.

Decided to pull the carb and give it a check. I had cleaned this one out last season so I figured it would be fine, but it only takes me 15 minutes to R+R on these. No dirt, sediment, varnish or buildup of any kind, it was all perfectly clean inside except for a couple tiny tiny drops of water in the bottom of the bowl. Put some Heet in the fuel tank, carb back on, ran it a few minutes in the shop then went for a test drive. Seemed better but still not quite right like it wanted to stumble every 15-20 seconds kind of at random, but maybe when it hits a bump...

Kept driving figuring if this was a coil failing it should heat up pretty soon and I would lose spark altogether. 45 minutes later, I'm still riding, and it's still running, yet better than it was. Decided to take it back to the health center and give it back, maybe the Heet in the gas made the difference? Pull down the hill and try to drive into the parking spot for the carts which is kind of an off angle right turn, cart dies. Got a couple stumbles out of it but that's it. I push it backwards about a foot so I can try to get it out of the way of the other cart, roll it down to the end of the path then suddenly it runs!

Try to turn it around, it dies again, roll it back down off the off angle "ramp" it runs again! OK... get it to run enough to make it back up the hill, back on level ground now its running perfectly fine. Back to the shop...

Paying attention to what it was doing by the health center I drive it up to a spot in the shop parking lot where I can drive the front end up on a similar "ramp". Still runs. I back down turn and drive the Left front wheel up, still runs. Hmmm, back down again drive the Right front up, It dies!
I pop the seat up, pull the ignition kill wire off. Now it runs again.

The frame is flexing just a bit when the right side goes up an incline and something is grounding out the kill wire. Intuition tells me it might have something to do with the ghetto rigged key switch which hasn't ever caused an issue before, but maybe this is the time to check it out. Sure enough the ground contact for the kill wire on the keyswitch is about a half a millimeter from the dash frame, and the cart frame flex is just enough to make it touch and kill the spark. Probably was close enough that some of the energy from the coil primary circuit may have been creeping across that gap and causing the weak spark I was seeing earlier.

Fix that (bent the tab back, and taped around the back of the switch)
put the dash back together and reconnect the kill wire on the engine. Re-check spark, now it's Strong and Bright purple blue jumping the plug gap. Take it for a ride and now it's running great again!

Might have had two issues here, possibly some water in the fuel causing an issue, but the major thing was the kill circuit wires were being shorted to the frame when the cart was turned just the right way (literally) or when it hit just the right bump in the road. Hopefully this short story will help someone else if they run across a strange issue like this!

[CP241]

Great find! I wouldnt have guessed that one!

I guess my question would be if theres a crack in the frame or some other damage causing it to flex that much, or if that's normal flex?

[Fairtax4me]

Last I checked this one didn’t have any cracks. Majority of my carts are old and have been bouncing around on rough roads here for many years, so they can be a bit wobbly. I don’t think this one is any worse off than the others as far as frame flex is concerned. It’s not what I would consider a “bad” amount, but it’s enough that you can kind of notice it if you pay attention.

[BBBHC]

Nice write up, and good trouble shooting!

I enjoy reading your write ups you post. Thank you for taking the time to do so!

[Springbok]

Nice work!