bogging down

[quadman22]

This is a 2001 400ex. K&n filter and full white bros exhaust. No other mods. I believe it was jetted accordingly because It was running perfect all last year and no changes were made at all. Let it sit for 3 or 4 months this winter and now it isnt running right. We changed the gas out for brand new stuff and we cleaned the air filter.

Started up fine after the winter and would idle but when you got around 1/2 throttle it would start popping and if you held it WTO it would die. Anything under 1/2 throttle and it runs fine. Idles fine too. It runs slightly better with the outwear taken off the ait filter.

Now it wont start very well but will eventually start and just have the same problem after 1/2 throttle. Carb got cleaned but im thinking about doing it again to be sure. What should i be looking for? I'm assuming i shouldnt change jets because this thing ran perfect for over a year now in all conditions. What would have changed to make me need a different jet?

Please help. Thanks for any responses.

[JOHNDOE83]

Take the air filter off and see if it run's any better, or disconnect the airbox from the carb and see if it improve's?

Did you buy any chance stick something in your main jet to clean it?

[CJM]

The jets are probably clogged, take them out run a small piece of wire thru them then clean with carb cleaner and see if it makes a difference. id also take apart the accelerator pump and check to makes sure its clean as well.

[quadman22]

i have all the jets out right now. On what i beleive is the main jet, the one where the needle sits in it, there is a check nut. Do you know where the nut is supposed to be situated? Is it supposed to be tight against the hex head that you actually put a wrench on to take the whole thing out? Or is it supposed ot be backed down?

Havent rebuilt a carb is way too many years:huh

[CJM]

Thats the main jet holder, the jet itself screws into it.

That part should be tight against the carb body.

[quadman22]

also, where is the accelerator pump? inside the carb?

[on the rocks]

sounds a lot like you secondary jet, i was a good was from home and mine gummed up and had to ride it home snapping the throttle feeding it more fuel through the accelerator pump, to say the least my thumb was tired! lol

[CJM]

Its on the outside, its round kinda shaped and has 3 small screws.

[quadman22]

Okay I'm looking forward ot working on this tonight after hearing all this. Thansk for the info.

Still unclear as to what to do about that check nut on the jet. I realize its supposed to go against the carb body, but that will happen if it is in any positions. How far away from the hex head on the jet is it supposed to be? Should it be tight against that head? Is that nut there to act as some sort of adjustment?

[TheAwesomehonda]

Originally posted by quadman22
Okay I'm looking forward ot working on this tonight after hearing all this. Thansk for the info.

Still unclear as to what to do about that check nut on the jet. I realize its supposed to go against the carb body, but that will happen if it is in any positions. How far away from the hex head on the jet is it supposed to be? Should it be tight against that head? Is that nut there to act as some sort of adjustment? I'm thinking you need to screw in the jet holder the whole way and then tighten that nut agenst the carb body. iirc

[CJM]

Originally posted by TheAwesomehonda
I'm thinking you need to screw in the jet holder the whole way and then tighten that nut agenst the carb body. iirc

bingo.

[quadman22]

Haha i just finally figured that out and then went and read those posts. You guys are exactly right. The jet only screws down so far (thats what i didnt realize) and then the lock nut tightens against the body.

[quadman22]

Completely cleaned the carb. Several times. No doubt that there is absolutely no dirt in there. Still doing the same thing. Cleaned out the accelerator pump and everything.

Runs slightly better now, barely any better though. Wont start unless pop started. Once it runs, it idles fine. It actually idles pretty high. No matter how much you turn the a/f screw in either direction, it doesnt change anything. Doesnt change the idle or how it runs.

What now??

[CJM]

Theres a filter inside of the gas tank that could be clogged, its in the petcock.

How are the valves?

[JOHNDOE83]

Have you tried what I suggested?

[quadman22]

Fuel filter was clean, havent checked valves, tried running without air filter. Nothing. Same ****.

Should i be able to infinitely turn the a/f screw? I can turn it 100 times and it doesnt look like its doing anything at all. Shouldnt it stop in one direction at some point?

[CJM]

Yes it should bottom out when you fully tighten it.

[quadman22]

Is there any chance I would need to adjust the clip on the needle? If so, which direction should i go with it?

[CJM]

Its possible, go down towards the point if anything. I like mine on the 3rd notch.