idle problems

[jeremy_283]

ok my 400ex doesnt idle perfectly if its warm and all it will idle for about 45 seconds then the idleing gets rough and it dies and it seems die almost instantly if i am pushin givin it all its got and then let off the throttle. so wat exactly do u think needs adjusting?

[prepracing]

you can adjust the idle screw on the carb. to make it idle a little higher and see if that helps

[YFZ450Ridr]

thats happened before to me and it turned out my carb just needed a little cleaning. take the bowl of the bottom and clean it out real good.

[GPracer2500]

What's your current jetting? Maybe your pilot circuit is lean. A hot engine will make a lean condition even worse.

[jeremy_283]

it started doing this last week....but now i am in the process of rejetting it so right now it has a 42 pilot and 170 main......... the main will prolly go down a size

[Buffalo400]

Originally posted by GPracer2500
What's your current jetting? Maybe your pilot circuit is lean. A hot engine will make a lean condition even worse.


Sure?
To me, I always thinking.....
leaner when cold... (because cold air have more oxygen)
Richer when hot....



Also, 42 is big in a 400ex .... Ok during winter but way rich during hot spring and summer....

What do you think?

[GPracer2500]

Originally posted by Buffalo400
Sure?
To me, I always thinking.....
leaner when cold... (because cold air have more oxygen)
Richer when hot....



Also, 42 is big in a 400ex .... Ok during winter but way rich during hot spring and summer....

What do you think?

You're right...I said that backwards...duh!

[jeremy_283]

even wit a dj 170 main my quad still is runnin lean and i check my plugs the correct way to like whoever was "bitting my butt" earlier on this post..... it seems alost white on the insulator except for some gray specks on one side of it then it is gray specks on the little top electrode thingy that bends off of the main part of the plug

[GPracer2500]

Your main jet has little to do with idle and small throttle opening performance. Was that plug reading after it had been idleing for a bit? Or did you do a WOT run and then immediately shut it down and pull the plug?

To get an accurate plug reading of each fuel metering circuit within the carb you've got to run the quad on that circuit ONLY and then immediately shut it down without allowing it to run on another circuit. For example, if you want to check your main jet: go run WOT for several passes and then shut it down immediately after running it at WOT. Don't let it idle, don't ride it at 1/2 throttle back to the garage, etc. If you do than the other circuits will contaminate the reading of the WOT circuit (main jet circuit).

Regarding your running issues: maybe you have an intake air leak? That can cause irratic idleing and lean jetting. Spray starter fluid or carb spray or something around all the carb/boot/airbox connections and listen for change in idle RPM.

[bwamos]

I think the idle circuit is too rich.

It sounds like he is loading up the engine with excess fuel at idle.

Try leaning up the mixture a little on the idle circuit.

To test, you can turn on the choke a 1/4 of the way.. if it makes it worse.. then it is rich. If it makes it better then it was lean. Odds are it's too rich though.

[jeremy_283]

i dunno wat WOT means but i ran my quad full throttle, mid throttle, and idle all while stayin in the same circuit from start to shutdown and every time the plug was a golden color except for the pilot jet which i adjusted and is fine now.... and it seems to die instantly right after i was givin it all it has at full throttle and it will die if i let it idle for a bit and then blip the trottle