Magneto damage
 

Picked up a used Manco 6150 Helix kart, GY6 150cc. The previous owner ran 2 screws into the cooling fan right into the magneto. Replaced it, got the kart running but I don't think the electric choke is working. Wondering if when the magneto got hit with the screws would anything have happened to the resistor for the electric choke. I read somewhere the resistor limits voltage to the choke in the event of a voltage surge. Don't want to buy a choke assembly without knowing if the resistor is good.

Thanks in advance

What is the symptom that leads you to suspect the choke isn't working?

There are numerous YouTube videos showing how to test the enricher to verify the needle is extending.

I replaced the spark plug, adjusted the valves, new air filter, oil change, coil, CDI module and checked the intake manifold for cracks. None found, but kart would stall coming to a stop. Mixture screw made no difference. I disassembled the carb, soaked it in a dip tank overnight, rinsed it out and blew it out with compressed air. Reassembled but still no change with the mixture screw. Thinking the plunger isn't extending into the enrichment port in the carb allowing excess fuel to dump into the carb. Exhaust smells rich too.

I've watched the YouTube videos regarding the plunger operation but I also read if the resistor took a hit it could fry the new choke assembly. That's my worry.

Thanks

Deficient petcock diaphragm . . allowing fuel to bypass carb via vacuum line?

https://www.youtube.com/watch?v=FnhSfgS0x4Y

Replaced the petcock also, noticed it was leaking when I did the carb work. Didn't help.

Thanks

Any chance the crankshaft-flywheel woodruff key was sheared . . which would throw off the pickup-coil ignition timing a bit?

Insert a probe into sparkplug hole to determine when the piston is at top-dead-center . . then observe if the flywheel T-mark is aligned with the case indicator.

The key for the magneto wasn't sheared but the key for the starter clutch was. The nut came loose somehow and the clutch just spun on the crankshaft when trying to start the kart. Used a puller to remove the clutch and replaced the key. High speed circuit is fine in the carb, it's the idle circuit that is troublesome.

Thanks

When you soaked the carb overnight, did you unscrew the slow jet or leave it in place?

Yes, every jet was removed. Ran a bread tie wire through each jet hole, made sure I could see light through every jet. I think I'll pick up a voltmeter and test the resistor. I need one anyway. More than likely the by-starter or choke is dumping fuel into the enrichment port when warm. If the resistor tests good it would almost certainly indicate a failed electric choke. Appreciate the help and suggestions from everyone. I'll update once the issue is resolved.

Thanks

Upon further review, I don't think my kart has a bystarter resistor. Went through the factory manuals, didn't see one for mine. The bystarter is powered by a "run/hot" circuit from the stator. Gonna pick one up & try it. Thanks again for all of the suggestions. If you have any more thoughts please submit them!

Thank you

Update on the bystarter or electric choke. Set up the choke with a 12V power supply and watched to see if the pintle would extend. After about 3 minutes the pintle extended as it should have. Looks like there is still a blockage in the old carb. Sometimes the only option with these carbs is to replace them. The kart sat a good while before I bought it. Issues like this are to be expected.

Thanks

Too many cobwebs in my head, so I'm struggling to remember how the enrichment circuit works. I thought the enrichment circuit was deactivated once the device warms up and extends, thereby sealing the needle to the seat; is that your understanding?

Yes, that's exactly how it works. There is a wax pack in the connector above the pintle. As the wax is heated it pushes the pintle into the enrichment port closing off the excess fuel needed for cold starts. It also brings the fast idle down with the decrease in fuel. My initial thought was the bystarter wasn't heating, keeping the pintle retracted and allowing excess fuel into the carb causing a rough idle and stall. The pintle is working though so the rough idle and stalling leads me back to a blockage in the carb or something causing the poor performance.

Have you adjusted the valves? Maybe the problem is at least partly there.

Yes, I adjusted the valves. Look at my posting from February 6th.

Thanks

Yes, I missed that.
I'm now wondering if the seat that the enricher mates with is eroded. If you had a torn diaphragm it would give you other issues (and you would have spotted it when you dismantled the carb), so I doubt that's it.
I'm following this closely as my wife's 150cc quad is having the same issue, but I haven't spent any time on it yet.

I took the hose off the vacuum port on the intake and cut a 1/4" off or so to make it fit on the nipple tighter. It seemed better but I ended up buying a Taiwan carburetor from GoPowerSports and installed it. I got the one with the bigger jets. It still doesn't start right up cold, takes a few attempts but it straightens out quickly. I can't expect too much since the kart sat for a good while. I took a gamble on it since everything from the factory was still there. I ended up taking the motor apart again to replace the crank seal on that side. Should have changed it when it was apart the first time. Oh well.

Thanks

I don't think that carb had a diaphragm. Has the typical needle & seat, float and jets but the petcock is actually the fuel pump I guess you could call it. There is a huge spring under the top of the carb with a rubber disc that rises as the throttle is opened plus a vacuum device on the side that has something to do with the throttle. Not a whole lot to them.

http://49ccscoot.proboards.com/threa...ctions-diagram

The diaphragm is in the fifth picture of the link you shared. It's a CV style carb, so the needle isn't directly acted upon by the throttle cable. You're opening the butterfly and vacuum is lifting the needle off of the seat.
Glad to hear that the new carb got it running.

Thanks for the explanation. I wasn't 100% sure how they worked, that helps. Looking at a friend's Echo weed whacker now. Carb on it is trash. Installed a factory rebuild kit but it only runs if I shoot starting fluid in it. Fuel filter isn't plugged, no hose restrictions, fresh fuel. Found a Taiwan carb for it for $16.00. Those carbs are apparently troublesome. One capped adjustment screw and it's the high speed jet. Pretty much throw away. Can't soak it in anything strong since there's plastic in it. Stale Ethanol fuel wasn't any help either.

The Echo doesn't have high and low speed adjustment screws?

No mixture screws, just one capped hi-speed screw. Soaked it in denatured alcohol to see if it will help, worked for my Manco carb.

http://www.zamacarb.com/carburetors/1156

I think we're good with the Echo trimmer. Installed the Taiwan carburetor but still had trouble. In the meantime I took the plug out of the mixture screw of the original carb and ground down an old pocket screwdriver to access the screw. I think I had the fuel hoses backward when I first rebuilt the original carb or the soaking did something. Switched hoses on the Taiwan carb and it fired up. It had no emission plug in the mixture screw but it wouldn't run right. Threw the original carb back on with the rebuild kit in it, adjustable mixture screw and fresh fuel. Seems fine. One hose was shorter, it's the return hose. I must have had it on the suction side or fuel inlet nipple. No wonder it wasn't getting any fuel. Another learning experience.