650 Cuts off after mods

Hey guys, I need a few suggestions on where I need to start

I just completed daves carb mods on my 2002 650L. Needle shimed, 55slow, 158main jets, drilled slide, removed air snorkle, the baffle removed from stock muffler, smog stuff removed. I fired up the bike, which ran really smooth for about 20 to 25 seconds then it just cuts off while idleing. Im not sure what could be causing this, but I suspect it may be flooding out. Once it cut off so I loosened the drain plug at the bottom of the carb, and some gas ran out of the drain tube. Does this mean the bike flooded. I did remove the side pannel thinking more air to the air filter would make the bike run better, but it still cut off while idleing after 20 seconds. I did replace the fuel mixture screw with a new fuel mixture screw made by the company "ziptie". I had to do this b/c the guy who owned the bike before me had broken off the mixture screw. Any amount I adjust the fuel mixture screw the bike still cuts out. :confused:

Did you connect the choke cable properly?

I would pull that fuel screw back out and make sure the o ring wasnt somehow damaged during install.

Will it continue to run at higher revs? Sounds like a vent line is not connected properly.:confused:

Whenever you loosen the drain screw, you should get fuel out the drain hose.

You can check the bowl running fuel level if you put some clear tubing on the drain hose nipple, pull the hose up above the carb, then open the drain screw. The fuel level in the hose will be the same as that in the bowl, and it should be just below (or a little below?) the top of the bowl.

But, its pretty rare to have the level too high on these bikes without fuel eventually coming out the drain hose while the drain screw is shut tight (the drain hose is also an overflow hose).

If you used the long 55 pilot jet, the slosh baffle could be covering the jet opening. Never had that stop mine from running, but have had it cause rough running before I trimmed the baffle.

Will it keep running if you keep blipping the throttle?


thanks Dave,

No if I keep the throttle up a bit past idle, the bike still cuts out after 20 seconds? Im not sure what to check next, other than pulling and cleaning the carb again. I read somewhere about a vacuum created in the tank that could be filling the carb with gas but when the fuel there burnt off no gas is going into carb b/c of a vacuum. or maybe I messed up when doing the smog removal.

on the smog removal I have a hose from the front nipple around the carb to the side nipple "diapraham" then a hose that has a "Y" in it is connected to the other side nipple, the other section of the Y has nowhere to connect now b/c of the hose that goes around to the "diaphram", is this correct, could the hoses be hooked up wrong.

Someone else mentioned about hooking up the choke cable incorrectly, I just put it back in the hole and tightened the nut, is there anything else I should have done?


I could be way off on this but it sounds to me like the gas is not getting in fast enough to replenish after an initial amount is burned off.

To check you could take a little gas or spray a small bit of starting fluid in the carb right after it dies and see if it fires back up. I'm thinking it will and run a few seconds untill whatever you put in there runs out.

Things that could do that kind of stuff:

Needle/seat stuck/clogged. Jets Clogged. Filter in tank clogged.

Petcocks. Messed up choke circuit.

Either way, If it was me I'd take the carb off and pull the jets, slide, float, needle/seat and clean everything and check proper operation of the slide and needle/float. Also did you use the short jet? or if long one did you check and modify the little plastic piece that covers it?

Hard to diagnose without looking at it but those are things I would do anyway.

Yes, with the extra info, sounds like a fuel flow problem.

Sounds like the choke is back in place OK, and I don't think getting the hoses wrong would cause this.


Please check cap for vent or maybe a pinched vent tube .

or take the tank cap completely off, you should take the fuel line that comes from the tank to the carb off and put it into a clear water bottle or something and turn the petcock on and see how your fuel is flowing.

I have no idea why this worked, but as someone suggested I removed the gas cap and started the bike, she idled for about 5 minutes to my suprise, so I cut it off, replaced the gas cap, started it back up, and she purrs like a kitten, best I have ever heard the bike run since I got it a few weeks back. Today after work, Im going to put a few miles on it and see how that goes. Thanks to everyone for all the suggestions and help, I certinaly have learned a lot here in the past week by going through all the olds posts. This site is great. JOHN

Your welcome.

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