Low speed surging, idle fluctuation

[jonr651]

My 2004 RSMV has developed a fluctuating idle, which seems to get worse the warmer the engine gets. It surges 800-1200 on the tach, and up to about 1500 rpm, then smooths out.

 

I'm due for a valve adjustment and am planning to do that soon, but this happened suddenly, in the middle of a ride. I didn't start gradually and get worse.

 

I pulled the carbs and removed the bowls and sprayed everything I could get to with carb cleaner, checked the float levels (all were good) and changed the fuel filter. I didn't split the carbs or completely tear them down yet.

 

Air filters are fine, and I'll probably do plugs just to rule them out.

 

I'm currently running some B12 thru it, and it seems a little better, but it's still there.

 

Hoping this rings a bell for someone. I'm going to do a complete tear down on the carbs when I do the valves, and re sync if no one has any other ideas.

 

Thanks for the help.

 

Jon

[etcswjoe]

Jon,

 

I was thinking fuel filter but maybe a vacum leak,take some starter fluid and spary it on your vacum lines and see if the engines revs, also does it get worse when its wet?

[V7Goose]

Check your choke - make sure it is all the way in and none of the plungers are hung up. Really plugged air filters can also cause those symptoms, but that will generally cause the engine to dog real bad at higher RPMs.

 

Also make sure none of the low speed mixture screws are working their way out.

Goose

Edited August 17, 2012 by V7Goose

[Cougar]

Goose, could maybe a bad coil be causing this , maybe on it's last legs?

Kind of kicking in and out and gets wrose when warmed up?

Jeff

[jonr651]

Which is the low speed screw? I can't identify it by the diagrams in the manual.

(they must use a different term).

It seems to be only below 2000 rpm. It runs smooth above that with no miss, although it seems the power is down a little.

I also seem to be smelling gas, especially when sitting and idling, but nothing is leaking and there is nothing coming out the vents or drains.

I'm going to check the plugs in the morning and see if it's one carb or an overall problem.

Air filters are ok.

 

Thanks for all the input!

 

Jon

[V7Goose]

Goose, could maybe a bad coil be causing this , maybe on it's last legs?

Kind of kicking in and out and gets wrose when warmed up?

Jeff

Theoretically that might be possible, but in reality l think not.

 

Which is the low speed screw? I can't identify it by the diagrams in the manual.

(they must use a different term).

It seems to be only below 2000 rpm. It runs smooth above that with no miss, although it seems the power is down a little.

I also seem to be smelling gas, especially when sitting and idling, but nothing is leaking and there is nothing coming out the vents or drains.

I'm going to check the plugs in the morning and see if it's one carb or an overall problem.

Air filters are ok.

 

Thanks for all the input!

 

Jon

Those are the air mixture screws located under each Carb near the drain screw. It is highly unlikely that they have moved on their own, but I have seen it happen if they have been set improperly. If the anti-tamper caps are still on them, I wouldn't worry about them at all. If the caps are off, then screw each in until it gently bottoms, then out three turns.

 

From your description, I'd still bet good money that it is a hung-up choke. Fully pull the knob in and out

a couple of times to make sure it is moving smoothly, then look at each plunger to be sure it has fully seated.

 

Goose

Edited August 18, 2012 by V7Goose

[jonr651]

The plungers are all working and appear to be seated evenly.

 

It starts and runs good on the choke, and even after I push it in, it still runs pretty good until it really warms up, then the idle gets hunting gets really bad.

 

I changed the plugs and they all seemed pretty even. Dk Grey to black on the threaded body, porcelain is white, and a med grey on the electrode tip.

 

Still have to get some starting fluid and check for a vacuum leak.

 

Thanks

 

Jon

[jonr651]

Well, after changing the plugs, the problem has disappeared.

Took her for a 100 mile ride this afternoon and smooth as silk!

 

Doubt it was the plugs, probably the B12 stewing in the carbs for a few days.

 

Anyway, thanks for all the input!

 

Jon