Erratic/high idle when warm, hunting idle when cold

Firstly hi all, not posted before but have been around for a while.

Just bought a DR350, fitted with a Mikuni pumper carb with standard jets (TM28) having been for a ride I found it won't idle properly when it's cold the idle speed hunts up and down a little. But when it's warm/hot the idle hunts more severly and if i rev the engine it sticks at 4000rpm increasing slowly to 5000rpm by itself, sometimes it will suddenly drop off and almost stall other times it just stays at 5000 until i let out the clutch or rev the engine again. Oh and it's very very hard to start without damp-start.

I've tried a few different things to no avail...

Adjusted the pilot screw - No effect whatsoever other than slight popping/banging when on leanest position.

Checked the slide wasn't sticking.

Dropped the needle a few notches (appeared to improve situation slightly)

Checked for air leak on carb rubbers.

Checked all jets for dirt-all were clean.

Checked float needle seal and seal O-ring.

Removed air filter (filthy) - Appears to have improved cold idle.

What should I be looking at next?

Can anyone point me in the right direction.

-Flank

Hmmmmm looks like I was searching under the wrong terms "Hanging idle" seems to have brought up a few similar threads, all suggesting the problem is a lean idle.

Will have a go with a bigger jet tommorow.

I would start looking for air leaks in the intake tract post-carb

I would start looking for air leaks in the intake tract post-carb

Aye checked that to start with but no joy :busted:

Forgot to mention the idle goes sky-high if I pull the choke out.

Hmmmmm, not having any luck here at all, I've checked EVERYTHING that there is to check on the carb and it's all fine, I've fixed all fuel leaks, cheaked the rubbers thoroughly for air leaks and even cleaned the air filter.

Yesterday I even tried a multitude of different jet sizes which all effect the general running as you would expect (small ones making it pop and bang big ones making it bog down)

BUT NOTHING I have done has had any effect on the hanging idle which randomly sticks at around 4000 rpm when revved regardless of whether it's running lean or rich or anything else. Sometimes it drops right back down and bogs out sometimes not.

So is there ANYTHING BESIDES the carb that could cause a random hanging idle? valves/timing/de-compression lever etc etc?

Does have a hot start or a tps?Not to familiar with these bikes, but ill try to help.

EDIT: I did some searchin around, and it seems that alot of dr owners experience the exact same symptoms as you because of a "sticking choke". I would clean all choke components(plunger,linkage,cable,etc), and then see what happens. Happy trails:thumbsup:

Does have a hot start or a tps?Not to familiar with these bikes, but ill try to help.

EDIT: I did some searchin around, and it seems that alot of dr owners experience the exact same symptoms as you because of a "sticking choke". I would clean all choke components(plunger,linkage,cable,etc), and then see what happens. Happy trails:thumbsup:

Interesting I'll have a wee-look tommorow, thanks for the input.

On another note I found that the Pilot Air jet was completely missing. SO I fitted one from another old carb I had laying about to see the results and it had quite a dramatic effect.

No longer does it hang at 4,000 rpm

It now hangs at 6,500rpm

Bugger

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now