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Old 06-24-2008, 09:32 AM   #1
Bigbird OP
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Question Airhead Noobie: cold idle adjustment?

Just got my first airhead - a 1982 R100RS, w/ 30K on it. The bike runs great but after having a K75 and an 1100GS that would idle fine when first started - using the choke- I find the R100 to be very "cold blooded". Even w/ full choke it won't idle steadily - without some help from the throttle - until I've ridden it for a good 10 minutes. So.... is this "just the way airheads are" or do I need to fine tune the idle? Increase the choke? Up the idle when cold?
Whattaya think fellow Airheads?
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Old 06-24-2008, 09:49 AM   #2
Bigger Al
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Start by adjusting the valves. Trying to do an idle set with valves that are out of spec is a waste of time, and will frustrate the hell out of you. Once you're sure that the valves are correct, then set the idle with the engine at operating temperature, per your manual. That should do the trick.

Nice bike, BTW, but some pics would be even nicer.
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Old 06-24-2008, 10:13 AM   #3
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Like Bigger Al said, start with the valves and then set the idle plus synch the carbs after thoroughly warming the bike with at least a 15 minute ride. Idling won't warm it up enough.

When synching the carbs, make sure to do the whole drill - balance the idle mixture, then synch, recheck idle mix, kind of an iterative process back and forth.

I also like to run the idle on my ST right around 1000-1050 rpm. I do that for slightly better oiling at idle, but I prefer all my bikes with a high idle for a couple of other reasons. But it also helps make for a smooth strong idle.

Also check choke cables closely. I had to dink around with mine a few times to make sure they opened and closed completely. Eventually I found the upper cable with broken strands in the cable splitter under the tank. Fixing that helped a couple of choke related issues during cold idling too.
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Old 06-24-2008, 10:44 AM   #4
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What these guys said!!! The biggest mistake folks make when syncing the carbs and that's where and when your idle gets set, is not having the bike warm enough to do the job. Riding hard for 20 minutes or more is required. Your carbs may be do for a rebuild also, make sure the choke cables are adjusted right and the enricher screws are tight also.

There's a carb sync rundown here http://wisconsin.airheads.org/content/view/33/51/
it applies using a twin max, vaccuum gauges or plug shorting method. Same sequence etc.
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Old 06-24-2008, 05:35 PM   #5
bpeckm
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Thumb /2 vs /5 idle

I own a 1966 r50/2, and when all is well with the world, it idles OK once warm. I ride a friend's r75/5 quite a bit, and it starts and idles like a ticking clock from the git-go. I am jealous of the later carbs!

You should idle smooth and fine once started, so something is amiss... synch and swim per posts above!
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Old 06-24-2008, 05:36 PM   #6
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Cold idle...

I played around w/ the carbs this afternoon - mainly just turning out the choke cale adjusters a bit and then the same with the throttle cables at the carb. Result seems a bit better - tho I'll have to wait til tomorrow to check the "cold start" and cold idle. But the bike runs great when warm, and settled down to a nice 1050rpms idle. I may have to reset the choke cable settings but we'll see.
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Old 06-25-2008, 04:11 PM   #7
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Quote:
Originally Posted by Bigbird
I played around w/ the carbs this afternoon - mainly just turning out the choke cale adjusters a bit and then the same with the throttle cables at the carb. Result seems a bit better - tho I'll have to wait til tomorrow to check the "cold start" and cold idle. But the bike runs great when warm, and settled down to a nice 1050rpms idle. I may have to reset the choke cable settings but we'll see.
HUH? To be frank ,there is a procedure etc. to properly adjusting the idle and syncing the carbs. "Played around" won't really do it. Do yourself a big favor, learn how to do it right. If by accident you stumble into a close to right setting you won't have a clue on how to do it again. The procedure is here http://wisconsin.airheads.org/content/view/33/51/
and a bunch of other places on the web. You can make or buy plug shorting adapters, or make the $4.00 manometer on the airheads site so no excuse to not do it right. Airheads need occasional tinkering so taking a few minutes to learn now will be a major help in the future. If you are still in the dark I'll wager there are some airhead types in your neck of the woods that will help you.
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Old 06-25-2008, 05:51 PM   #8
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Quote:
Originally Posted by bpeckm
I own a 1966 r50/2, and when all is well with the world, it idles OK once warm.

Maybe you're still using the stock # 35 idle jets? I use # 40s on my R50. Idles fine when cold and is immediately rideable after starting.

Sames goes for my 100PD, as I upped the idle jets to the next number. Never need to choke it to start.
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Old 06-25-2008, 07:38 PM   #9
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Airhead Noob also

Another Noob (1988 R100GS) with idle problems...After 5 mins of idle with choke and about 3 miles of riding with half choke, the bike still won't idle without choke...just lugs down and quits if you don't hold a small amount of throttle. With the choke half on (in the detent) there is some grey smoke. I just got this thing tonight, so haven't had a chance to do the 20min of riding warmup recommended earlier...on the agenda for tomorrow. Any other suggestions from you more experienced Airhead riders out there? Thanks!
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Old 06-26-2008, 05:36 AM   #10
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Talking

Hi
Quote:
Originally Posted by Bigbird
Just got my first airhead - a 1982 R100RS, w/ 30K on it. The bike runs great but after having a K75 and an 1100GS that would idle fine when first started - using the choke- I find the R100 to be very "cold blooded". Even w/ full choke it won't idle steadily - without some help from the throttle - until I've ridden it for a good 10 minutes. So.... is this "just the way airheads are"
To answer the question: Yes, this is normal.

The K75 and 1100GS have fuel injection and adjust the mixture electronically "on the fly" ... but on the airheads, you have to do this manually. Generally I start the engine and try to ride off ASAP, removing the choke completely after a short distance. It idles well after a few km in warm weather.
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Old 06-26-2008, 07:32 AM   #11
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Joerg, I have been trying out what you and Lornce have said about getting out on the road fairly soon after getting running and getting off choke asap, and maybe just because of the warm weather we've been having here, but its been working pretty well, I must say.
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Old 06-26-2008, 05:32 PM   #12
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That's the advise of car manufacturers as well. More wear can result by operating a cold engine longer. So driving-off gently once started is the best.

In my case, a richer idle jet helps a lot (from 45 to 50). Removes the cold-engine stumbling without the soot. And I never use the choke
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Old 06-27-2008, 03:34 AM   #13
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RS idle :update

Just to update all who've responded to my original query, the bike is running very nicely now. If I move out right after start up, I can move the choke to the midway point in about 3-5 minutes and to the "off" position in about 10 minutes - this in mild air temperatures of @ 70-75F. Once up to operating temp, the engine settles down to a nice, stready idle of @ 1050rpm .
I think I'm gonna love this bike!
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Old 06-27-2008, 06:07 AM   #14
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I"ve also gotten into the habit of taking right off. Someone told us up here in the north along time ago that it was better to get a vehicle moving as it would warm up quicker and be easier on the moving parts. May have been click and clack. Both my airheads though can have the choke shut completely off in just a minute or two of running. Not sure why one would take 10 minutes.
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Old 06-27-2008, 06:19 AM   #15
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Hi,
Quote:
Originally Posted by Bigbird
If I move out right after start up, I can move the choke to the midway point in about 3-5 minutes and to the "off" position in about 10 minutes - this in mild air temperatures of @ 70-75F.
Not normal. You should be able to run w/o choke after 1 mile at latest (idle may not be stable at that point, but the engine will at least run stable!)

I suggest to ride her for at least 30 min, then perform a complete idle adjustment (takes 2..5 min).

If that does not help, disassemble & clean & reassemble & adjust carbs fully. I start to have doubts about the cold starting system ...
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