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Discussion Starter · #1 · (Edited)
so I got a 2001 400ex on trade. Ran good just didn't idle for squat. I'm new to quads to boot but I'm mechanically inclined. Well the quad does weird things when I started it today I had it idling then it just started revving extremely high then it went down and wouldn't idle at all and die. Mind u I only have an aftermarket muffler on at this point the quad is still pretty much stock. I noticed it was leaking gas out the overflow but it still starts and when I drove it it bogged down at full throttle. I'm not sure what to make of this but I will say that the cable underneath the carb is broken. Idk what it is but I know its a cable that runs from an adjustable screw into the carb from the bottom. Is the cable important can it be causing this dilemma?
 

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You have multiple problems (mostly carb) - the high idle might be a vacuum leak, but get the carb fixed first

Not wanting to idle could have something to do with the "broken cable" under the carb. That cable is a flexible shaft that attached to the idle set screw. A new one is about $12

First question - can you hold the engine at idle using the throttle? If you can, you might be able to turn the screw the cable was attached to and set the idle speed. Bogging at full throttle is either too little or too much fuel - to figure it out, ride it and at full throttle put the choke on - if it makes it run better with the choke on, it needs more fuel (bigger main jet or clean the jet it has), if it doesn't help, then it's probably getting too much fuel (needs a smaller main jet or sometimes the jet has just fallen out or even broke and just needs put back in the main jet holder)

Fuel leaking out the overflow has many possible causes - the primary cause is not turning the petcock off when stopping riding - if it leaks out while riding, bad float needle, bad float, damaged or dirty float needle seat, loose or not properly seated drain screw or possibly a defective or damaged stand pipe in the float bowl

Get the carb gone through by an experienced mechanic and most likely all the problems will be gone
 

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Discussion Starter · #3 ·
I can hold the throttle to idle,I have actual had the carb apart and was investigating how things work, it has a new muffler on it, wouldn't it need rejetted for that, I heard it would be too lean. Which I have a jet kit on the way and I did order the set screw and all that last night. Hope it helps. I'll try to upload the video I took yesterday of it running.
 

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In the video, you have the petcock in the off position - it ran about as long as it should have on just the gas in the float bowl.

Just changing the muffler only affects jetting on the top end (wound flat out) - you might jet up from a 148 (stock) to a 160, but that won't affect the idle. The way it was idling in the video, I would say it needs a little more back pressure on the exhaust or the fuel/air screw needs to be adjusted. Do that with 93 octane fuel, the fuel turned on and the engine fully warm. Ride for about 5 minutes before trying to set it and use a fan to blow air across the engine while making the adjustment.
 

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Discussion Starter · #6 ·
I left it off on purpose. It ran a lot longer with it off before I actually took the video. I have jets on the way and a new idle adjustment screw/cable assy. This is all new to me its weird but intriguing. I greatly appreciate all the help and ill post after I get all my parts and try fixing it.
 
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