Idle won't fall

[Erich Z]

I was riding around a bit today and noticed that the idle would not fall below 3k rpms eventually - just kinda hovered there. I got it to fall by revving the engine quickly, then it settled to about 1500, which seems to be about normal on this bike. Any ideas what could cause this? The bike is new to me, has about 6k miles so it hasn't been ridden much in a while.

Also, when checking the oil on these bikes, what is proper procedure? Do I set it on the sidestand and check while hot? Center stand? Like I said, I'm new to all this.

[tconroy]

Your hanging idle is probably due to an air leak between the carbs and the cylinder.If your bike has intake boots check for cracks and also replace the o rings in the intake boots.These get brittle and crack.Spray some wd 40 around the intake boots to see if your idle drops any.If it does that means you have a leak.It is not always detectable this way but it's a start.Your oil should be checked after the bike has sat for a while on a flat surface and with your center stand down.Your idle should be between 900 and 1100 rpm's.

[Erich Z]

Hmm, rode it again tonight and the same thing happened. It only happens once the bike gets really warm, then the idle doesn't like to fall, or if it does, it falls quite slowly. I tried the WD40 test but didn't notice an idle drop.

Also, once it does settle down it tends to be about 1200 rpm when cold, but more like 1500-2000 when warm, and that seems high to me. I looked for the idle adjust screw but couldn't find it. Any hints? I have a Clymer's but the illustration shows a screw I just don't see. I'll take some photos to see if that clarifies anything.

[robertbarr]

Pardon the apparent plug, but I get tired of typing all of this:

http://www.cycleorings.com/intake.html

[tconroy]

Hmm, rode it again tonight and the same thing happened. It only happens once the bike gets really warm, then the idle doesn't like to fall, or if it does, it falls quite slowly. I tried the WD40 test but didn't notice an idle drop.

Also, once it does settle down it tends to be about 1200 rpm when cold, but more like 1500-2000 when warm, and that seems high to me. I looked for the idle adjust screw but couldn't find it. Any hints? I have a Clymer's but the illustration shows a screw I just don't see. I'll take some photos to see if that clarifies anything.

It is in between the carb bowls.You probably have an air leak.THere is an o-ring in the intake boot and they are probably hard and cracked.These need replaced.Go to www.bikebandit.com and look up your bike .You will find a shcematic that will show you what Im talking about.Also order those o-rings from Robert who's post is right above this one.

[Dave8338]

That haunting idle is almost certainly the orings that Tim (tconroy) mentioned. Try some carb cleaner spray or starting fluid on the carb boots up where they meet the head...the idle should pick up...even if it does not, those o-rings need to be replaced to get things to run there best. Robart is THE source!!

[tconroy]

I replaced my o-rings and boots to fix my high idle problem,11000 miles later it still runs and idles nicely.It will also make your bike run cooler.sucking more air into the cylinder will cause it to run hotter and that's not good.Use some seafoam in the gas tank and that will help also.Let us know how it goes.

[Erich Z]

This is the schematic of my bike's carbs, what O-rings am I replacing, and where is the idle adjust screw? Thanks for being patient with a noob.

[tconroy]

This is the schematic of my bike's carbs, what O-rings am I replacing, and where is the idle adjust screw? Thanks for being patient with a noob.

Item # 73 is the adjuster.It is between the 4 carbs.Look behing your carbs from the bottom.It is a nurled screw that sticks out right in the middle. Look in your clymers manual under carburetors it has a better diagram and tells what each part is.
Be careful when adjusting this.You need the bike warmed up and it gets hot right there.Where a glove or wrap a shop towel around your hand.Counter clockwise will turn your idle down.The o-rings are not on that diagram .They will be under the cylinder head diagram.i will see if i can find it for you.

[Nessism]

Photo stolen from Robert Barr's site, http://cycleorings.com/

[benwitt11]

Thank you for posting this question. My bike has recently started doing the same thing, I just hadn't gotten around to searching for answers yet. O Rings are ordered, (thanks for making it so easy!) We'll hope that after close to 30 years, the bike just needs $3.00 worth of parts!

[tconroy]

Good pic too! That o-ring is toast!Mine were'nt cracked but they were flat as a pancake.These alone will cause major idle hangups when the bike warms up.Replace these and then adjust your idle.Add some seafoam to the first couple of tanks and then see what happens. this may be all you need to fix the problem if the bike runs well already.