My buddy has a 200M ATC and I just rebuilt and cleaned up the carb for him. Before I rebuilt it, we could only get it to stay running if we kept dumping starter fluid in it, but since I rebuilt it, it stays running at idle only with the choke completely out.

If the choke is pushed in, it will die out. Also, if you press the gas, it seems to bog down, rather than rev up. I messed with the carb adjustments and to no avail. One thing I noticed is that when I turn the petcock on the fuel tank to the complete on position, it slowly trickles out. Is this normal?

Any suggestions, information, or things to check? I'm new to this type of thing. Thanks guys.

 

Nope. Not normal. And the reason it runs on choke is because that minimal air passing by is all that is required for what little gas appears to be entiering the fuel bowl.
Those petcocks can sometimes get clogged up and cause a restriction. But another thing to look at would be to see if the vent line (the upper most fuel line on the carb) is stopped up. That line runs towards the ground like the overflow line and sometimes mud can splash up causing a blockage. If the carb bowl doesnt get this vent, it doesnt draw gas from the fuel valve properly,...sometimes not at all.
To really test this right, you neeed to be able to get the machine running at idle and while doing so, unscrew the overflow screw on the bottom of the bowl to let gas runout. If it dies, it is the vent or fuel petcock causing the problem. If it still runs with fuel draining from the carb, shut off the choke and see if it catches up then.

 

Well when I had the carb apart, I sprayed carb cleaner through that overflow hose to make sure it wasn't clogged. So I don't think that's the problem. I believe the petcock is to blame, but I also sprayed that out to attempt to unclog it, and it still just trickles out. What would you suggest I do to properly clean it? Or should I just replace it completely? Thanks for your help.

 

Well, if it just trickles out with the fuel line unconnected, it is either restricted in the valve portion itself or the filter screen ontop of it going into the tank is clogged....or both...OR the fuel cap isnt ventilating.
Take off the fuel filler cap and see if it runs out correctly.
If not, remove the fuel valve from the tank and disassemble it to clean it.

 

Well the fuel cap is venting I believe, because I opened it when it wouldn't start at all, and that's when it finally started staying running for a few minutes. I'm gonna guess it's something to do with the petcock. Any way of cleaning it that you know of? Take it out and soak it in something? Or just replace it completely? Also, you say there is a filter screen on top of the petcock? I'll have to take the petcock off and look at it when I get a chance. Thanks again for your help...

 

My 1985 250SX has the exact same symptoms. Before I went through the carb, I verified that the tank valve was flowing well, at least on the "reserve" position (it was not flowing well on the standard position, but I only had 3/4 gal in the tank). When I get home I'll double check that it is still flowing well on the reserve setting. Does anyone have any other ideas for the same symptoms?

Thanks,
Michael Pliska

 

Well the petcock on the tank is flowing fine. Everything checks out good. Went through the carb again, and it ran alittle stronger after that, but still won't run normally. Any more suggestions would be appreciated. Thanks.

 

Again, your problem is lack of fuel or excess air. You have confirmed fuel delivery to the carb and you have verified that no cracks in the intake is causing a lean condition, so your problem is most definately in the carb itself. I've seen these things tanked in super sonic cleaners for 2 days straight and not clear the small passages on the idle cicuit side.
If everything is set to spec and assembled correctly, you may simply be looking at a mandatory carburetor replacement if repeated cleanings arent unblocking the restrictions.
These things can wreck havoc on anyone's day, but the entire fuel system on these trikes are the easiest on the planet to diagnose and leave little room for anything to overlook. As far as I can tell, you have covered the basics unless someone else here as another idea.

 

Are there any specific idle bleeds to look for and unclog? Mine is doing the same thing still.

Thanks,
Michael