Ok. Heres one for the mechanuks! I have a 4 stroke, 6 1/2 hp in one of my gocarts. Was going like a bat outta hell right up till I made a ' tight right' at high speed off pavement onto gravel. With no warning whatsoever, it shut down.I Closed the choke & Started up no problem. As soon as I open the choke, even a little bit, the engine stalls out! I was able to drive back home, about 1/2 mile with the choke completely closed. Of course at about a 1/4 power at full throttle. Everything looks ok yet still stalls out as soon as I open the choke. I'm looking for any possible solutions. Thanks

   

theory:sounds like it could be a fuel starvation problem, and the choke is makn=ing it possible to suck more gas through to the engine. My guess is you have a jet or needle valve stuck in your carb due to bad gas.

My reccomendation: try starting or running the engine with your hand covering the air intake to force some high flow of gas through your carb. of course this will stall and flood your motor, but it might very well dislodge whatever is giving you greif.

if this works, then I'd follow up with a fresh tank of gas, and add a small bottle of carb cleaner to the gas can instead of the tank.

if it doesn't work, then forget everything that I've said and come at this problem with a fresh approach and an open mind.

   

Fuel starvation. Spend 3 bucks and replace all of the gaskets for the fuel system. One of them is likely coming apart. Clean everything. There's ethanol in fuel now and it kind of eats things not designed for it.

Much less likely...I'd give it about 1%...bad wire or connection on the magneto. You'll never find it, but spend another 3 bucks and replace it.

if all of that fails? Hit it with a hammer for a while, then go get another engine. They're damned near free now.

   

Thanks guys, i'll try these out in the morning. I seriously considered your 'hammer solution' Rev as I do have a new spare in the work shop! Fortunately, my son was with me and was able to convince me that this was not in fact 'the best' solution!

   

Sounds like a carb problem but dont waste time replacing all the gaskets unless you see a fuel leak,more like you have to clean out the 3 jets.There will likely be a speck of dust in one of them and im guessing the low speed circuit.You have 3 jets in your carb,one for low speed(idle),one for mid throttle and one for full throttle.The only way too fix it is rip the carb apart and physically take each jet out and blow out the hole with compressed air.Of course tapping the float bowl with a wrench might also loosen whatever is plugging the jet.Easiest way to tell is get it running and work the throttle,if it works fine at mid range or full throttle then your low speed jet is plugged.Whatever you do dont try clean any of the jets with a stiff wire.

If you need more help then message me and ill ask my 16 year old niece,she's sponsered by Yamaha and her dad was instrumental in fixing yamaha's carb problems with the old yamaha phazers that used to see one side of the engine go through meltdown at alttitude.

   

Thanks Zig. Looks like a good cleaning is the first order of the day. I'll lrt you know how that goes.
I just had another thought. If all the above fails, I could just change the carb for the one on my spare engine. It's a 5 1/2 hp, but the carbs will switch over!

   

try the cleaning first Yogi, the carbs might switch over easy,
but they may be jetted diff..

i know its only one horse, but......

   

So I buggered around all afternoon. Tried all the suggstions, ( except the BFH)!
Tomprrow I'll swap carbs. In the meantime, I backed the govenor off of the cart I let the kids drive, and took that one for a good rip. Let me tell ya, 'gettin stoopid' on a cart with knobbies is a whole different ride when one is used to driving with smooth racing tires. 'Cornering at high speed' IS NOT reccomended. I have a bit of welding to do now!

   

I've had a series of gasoline problems with all of my small motors recently, its almost like the gas I'm buying just doesn't have the shelf life that it used to.So now, I'm adding stabilizer to all jerry cans that aren't for immediate consumption. I had to dick around with a jet that was sticking in my mower this summer, and its cheaper to stabilize the gas, than it is to spend the time to clean crap like this.

   

Hell, Lily. At 'my age', two strokes are all 'I' need. Then it's 'her' problem!

   

I used 'brand new gas' right from the pump today. And I would be inclined to agree with you on that one, but the other carts and lawn equipment are all running fine on the same gas.