400ex cutting out at idle

[matt400g12]

My 2005 400ex cuts out at idle. Even once I warm it up it will abruptly cut out and shut off almost like it misses a spark. I had the carb rebuilt and cleaned, and I adjusted my valves to perfection. I can keep it running if I hold on the throttle but it still tries to cut off. I dont think it's the timing because it ran perfectly fine recently but just all of a sudden it started happening. here is a video:
http://www.youtube.com/watch?v=4yOQLc2Wcdg

[CJM]

Personally clean the entire carb, take the bowl off, accelerator pump, clean all the passages, jets, etc. Also clean the slide. just cause you think its clean, it might not be.

id also change the plug.

Remember simple stuff first.

[DragonGunner]

Personally clean the entire carb, take the bowl off, accelerator pump, clean all the passages, jets, etc. Also clean the slide. just cause you think its clean, it might not be.

id also change the plug.

Remember simple stuff first.


Yup....you could also try a bigger pilot jet, and or raise the needle a notch which will allow more gas in as it idles.

[matt400g12]

alright I think I'll go with a 42 pilot. I did clean out the pilot jet and it ended up running good for a bit before cutting off and doing the same thing. But that could be because the gas is somewhat old.

[KKiowaTJ]

Yeah, Fresh winter blend gas wouldn't hurt with the cold blooded 400's, Or add a dixie cup or two of heat to the tank. CJM nailed it, That's where I would start and most likely the problem.

[CJM]

How old is the gas? Once a friend let his 400 sit for approx 3 months, stabil added to the fuel and everything. Damn thing wouldnt run till we threw in fresh 93 octane.

[KKiowaTJ]

How old is the gas? Once a friend let his 400 sit for approx 3 months, stabil added to the fuel and everything. Damn thing wouldnt run till we threw in fresh 93 octane.


That's because stabil is pure **** to use. It takes octane out of the fuel or at least did on my R1. Ran 50/50 during summer and 93 the rest. It had a full fresh tank of 93 and stabil, Lost all the octane and wouldn't start a fire for chit.

If anything, Use sea foam, That will clean out the valves, carb and burn the fuel quicker so you can add fresh gas. Best bet, Drain out whats in it and go get fresh 90+ and start there with no additives so you can pin point it. To each their own though

[Its_a_Honda]

there should be a flat head screw on the bottom of your carb not your fuel to air mixture its a bigger looking nob turn it to the right to lower your idle or to the left to up your idle. make sure you dont mess with your air to fuel.

[matt400g12]

there should be a flat head screw on the bottom of your carb not your fuel to air mixture its a bigger looking nob turn it to the right to lower your idle or to the left to up your idle. make sure you dont mess with your air to fuel.

yeah I had it turned all the way. I've had problems with that before, so I knew that wasn't the problem. I figured out it was the pilot jet clogging. every time I ride it I have to clean it cause it gets clogged. I ordered a 42 to fix it, along with a dynojet kit. I'll post the results once I get it in!

[matt400g12]

I put in the new 42 pilot along with the dynojet kit, it helped a little but its still doing the same thing. Its GOTTA be the gas. I'll swap it for fresh gas when I get home and see what happens