Idling too fast when warm

Hey boys. I need your help. My 2007 DR650 is idling way too fast once it warms up. I don't think it is the choke because I have one of Jesse's hand chokes installed. I did do my 7500 mile service myself (including the valve adjustment) and fixed the potential NSU problem a couple of weeks ago. I don't think the problem is directly related, because I've only noticed the high idle the last couple of days of riding... That being said, it is highly possible.

I'll check for vacuum leaks or anything like that this afternoon... but I wondered if y'all had any ideas?

Thanks a ton.

I should probably add that my DR is completely stock except for the hand choke...

That is the one thing on the bike that you are allowed to tweak. Just set the idle to a lower rpm. I seem to have to increase my idle for cold starts and then decrease it when it gets warmed up.

Thanks man. That's what I figured. I was just paranoid that I did something wrong when I adjusted the valves. You know how we newbs are... ;-)

+1 If you are already at a high idle speed spark advance will cause the idle to increase even more. If it isn't just a simple idle speed adjustment check for vacuum leaks as the primary issue. Anything to do with the vacuum petcock system could be a source. The new hand choke as well. It needs to seal off the port properly... double check the rubber seal at the end and make sure the spring is actually compressing towards the end of the retainer nut travel so you know the rubber seal is being pressed against the port in the carb body. Intake manifold leaks. If your bike is bone stock a lean condition can cause unstable idle. Maybe just a pilot screw adjustment. Another source of a leaning mixture would be the plastic spacer on the stock needle. These are known to wear in the area where they contact the D-shelf in the slide. As they wear your mixture becomes leaner and leaner. Check this on your machine. If it does show signs of wear you can flip the spacer and regain the height of the needle that has been lost.

Thanks mxrob. You're the man.

I've had the hand choke on there for several months now... No problems. This idle problem seemed to pop up suddenly, thus the reason I feel like it may be more than just a pilot screw adjustment...

I'll dig in this afternoon and see what I come up with.

My biggest fear was that I adjusted the valves too tight... A higher idle wouldn't be a result of valves being overly tight would it?

No. If the valves are too tight, it makes the bike hard to start.

Alright... Checked for vacuum leaks and couldn't find any. Also checked the intake manifold, and couldn't find any. The throttle cable is well lubed and not stuck either. When I went to adjust the pilot screw, I discovered that I can tighten it and increase idle speed, but no matter how far the other direction I go, the idle speed doesn't really decrease once it reaches a certain point, which is still high... Any ideas?

My DR has what I consider an odd idle adjustment screw. There is an outer screw that is held in place with a lock nut, and another screw that runs inside of it for fine tuning. My outer screw was adjusted high enough that the throttle stop was hitting it, and I couldn't lower the idle any more using the smaller screw. I lowered the outer screw enough so that the bike would just barely die. Then I used the inner one to knock it up where it needed to be. I also had to re-adjust the idle mixture after that, as the butterfly was less open, so I'm sure the slide was less open than it had been before.

With it the other way, the throttle was open enough that adjusting the idle mixture wouldn't quite kill the bike.

I can't think of any reasons this would happen out of the blue, but it's still something to check.. Clear as mud??

Definitely sounds reasonable. Thanks jqueen! Now you boys feel free to get a good laugh at me with my next two questions... It won't hurt my feelings. I owe y'all that much... But...

1. So if my pilot screw were adjusting properly I should be able to "kill" the bike by running it all the way out. Correct? Since I can't, something is up there... Maybe need to try what jqueen suggested.


2. As far as vacuum lines go... When you take the seat off, there is one vacuum line running from the carb, under the seat, not attached to anything. Sort of "snorkeling"... Correct?

Thanks a million.

1. All the way out or all the way in *should* kill the bike by making the pilot circuit too rich or too lean (respectively), but that's not always the case. Just because it doesn't kill the bike doesn't mean that it isn't working correctly. As long as the "lean peak" falls within 1T open and 2 1/2T open on the fuelscrew, the pilot circuit is working correctly.

If you can't get the idle low enough with the fuelscrew all the way in and a smaller pilot jet than you should be using (i.e. the carb should be un-runnably lean at idle), then the carb slide is too wide open or you have an air leak that's keeping vacuum high enough (due to RPMs) that you're pulling excess fuel from another jet (often the MJ).

2. Can't answer this one without looking at a bike; I don't recall how the factory hoses are routed.

Alright boys, thought I owed you an update. So I'd cleaned the air filter about 500 miles ago so I didn't do it again when I did the valve adjustment, etc at the 7500 mile service. Well, just for giggles, I opened up the airbox to have a look. Some kind of animal, probably a mouse, had built a home in there and filled it with my dog's food. I knew that dog was looking skinny!! ;-) Anyway, I cleared that out, cleaned and reoiled my air filter, and voila, idling like a charm. Just drove it to work which is about a 25 mile ride and even at its hottest it was idling just fine.

Now, this thread is clear evidence that I'm no mechanic, and I have no idea what effect that may have had on my idle speed, but I do know the problem seems to be fixed...

Gotta love living in the country!

Thanks for the help fellas.

Glad it worked out. :smirk:

Hey, at least a mouse didn't chew through the wires...

Two of my neighbors got to enjoy that fiasco this year. :smirk:

+1 on that... Thank goodness... All I know is the cat is definitely getting a little less Fancy Feast from now on. Dadgum thing is going to have to start pulling its weight!

LOL! Classic carb tale. :smirk:

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