Idle

[MIAirhead]

:dunno Without adjustment of any kink my 84 R100RT idles at about 4000. It just start, and does not seem to go down at all. I have just adjusted the valves but I don't see how that could effect the idle.

[lostboy]

If your exhaust valves had no clearance before you adjusted them, and the carbs were adjusted to make it idle in that condition, correcting the clearances results in a very fast idle. Start by backing the idle speed adjusters off on both sides until you reach an idle speed you can live with, then properly synch them.

[PineGreen]

I had same problem on my 82 RS. A buddy fixed it. While the biike sat there idling at 3000rpm he pulled one of the plug wires off one of the plugs and the bike kept idling fast with a very small drop in rpm. He reinstalled it and removed the other wire and the idle dropped down tremendously. He reinstalled the wire and the bike revved back up, he then adjusted the idle screw on that carb till the bike idled at about 1000 rpm and everyone lived happily everafter

[orbitangel]

:dunno Without adjustment of any kink my 84 R100RT idles at about 4000. It just start, and does not seem to go down at all. I have just adjusted the valves but I don't see how that could effect the idle.

InsertDisk,

It has been my experience that OFTEN, when the idle RPM is too high, especially when it is WAY too high, the ignition timing is wrong - firing much too early, that is.

Pull the timing cover plug, both spark plugs and the front cover.

Plug the spark plugs back into their leads and let them lay on top of the cylinders so they make a good ground connection and can be observed by YOU.

Insert the correct Allen wrench into the end of the crankshaft (alternator rotor bolt) and turn the crankshaft SLOOOWLY, in the proper direction (the direction which will TIGHTEN the alternator rotor bolt, clockwise if you are facing the front of the engine.) The ignition should be ON, of course, after you are all set up.

When the plugs fire, stop and look into the timing window. You should be staring directly at the "S" mark on the flywheel, centered in the timing hole.

You can back-up the crank about 1/4 revolution and try it again. Sneak-up slowly and carefully on that spark. If it happens too soon (possibly several degrees BEFORE reaching the "S" mark) you have just identified one good candidate for causing a high idle.

Adjust the ignition timing until the spark occurs right on the "S" mark and go from there.

If you have a nice, bright timing light you only need to pull the timing plug and fire-up the engine. Initial advance (low idle) at the "S" mark, full advance at the "F" mark.

Good luck!:thumb

[sumran]

The adjustments that have been mentioned should solve your problem. Now that you have your valves adjusted properly, you will be amazed at how well your machine runs. Valves, timing, then carb adjustments (though you will have to get your idle down to check the timing). Carb syncing is simple, but not easy. There are lots of threads on the subject. If you can get an accomplished airhead wrench to help, you will benefit from it.

I would not pull the plug wires while the bike is running on your model year. There is a risk to the electronic igniton. You can ground the spark plug to identify which cylinder is the problem, just don't leave an open circuit.

[MIAirhead]

I will try the fixes, I'll make a sync I found on Airheads. In west MI I have not found any airhead wrenches, but the dealer (Grand Rapids) does me well when I need parts, and such. I found a body shop that will pant the faring. Its run by a couple of old race car guys who just don't want to retire it think. I hope to get the running good enough to go south in the summer, I got it last August. It ran OK, just started hard, that is why I did the valves.

Thanks for advice

[26667]

check to see if one of your throttle cables is hanging up. Look right where the adjusters are near the carb itself. mine did that and scared the shiite out of me one day. One of the metal "ferrules" (?) was sitting slightly ajar on top of the other. It had just satyed open on one of the twists of the hand grip.

[sumran]

I'll make a sync I found on Airheads...

Thanks for advice

It works very well. If the sync is way out when you attach the device it will draw the fluid into the high vacuum carb.

[barryg]

Check Ur choke position. Should be no chock in off position and full choke to both carbs in on position. Chock cables could be out of sync., just something else to check while trouble shooting carbs.

[88bmwJeff]

Don't forget about the mechanical advance unit. Follow link for more information.

http://w6rec.com/duane/bmw/advance/index.htm

[PGlaves]

Check for air leaks.

[MIAirhead]

:dunno I just got back from taking the Rescue Van to Indiana to pick up some dogs from Amish breeders, (they give us dogs that are too old, or have issues, or just getting out of the business). We even had a flat on a busy 4 lane, but some nice gentleman stop and help me change it...

Back to the Idle, I start the bike, idle was where it should be, about 1000( I did not look too tired tonight). Smooth start right up, nice smooth idle. Being as I have dog chores I did nothing more, (we have over 100 dogs).


So I going to ride tomorrow, and see if the idle goes up when warm. I know I have electronic ignition so I don't think it could be the springs as I do not think they have any on an 84 100

[boxermaf]

The springs are in the "bean can" or ignition trigger unit, and are part of the advance mechanism. The weights can sometimes 'stick' if the inside of the can gets corroded or gummed up, but this is generally NOT a warm .vs. cold type of thing - usually it is when coming to a stop at an intersection after running at speed, and the idle speed doesn't go down. If a quick blip of the throttle, or shutting off the engine and restarting it corrects the problem - it might be a sticking advance mechanism as the sudden decel/accel of the mechanism (Driven from the front of the driveshaft) often "unsticks" them, if they are the problem.

I've got 'em in my '82, and you've got em in your '84 (and have them in all airheads).

I'm still leaning more toward an air leak, or misadjusted carb now that you've adjusted the valves. If the carbs aren't adjusted and synched when the engine is good and warm, that can also cause a high idle speed when the engine does get warm. If the valves were way out of wack before and the carbs had been adjusted for that condition, then something like this may be the culprit.

[88bmwJeff]

I replaced the springs in my bean can. BTW, how many miles are on the bike? Mine needed replacing around 90k. If you need the springs, Motobins sells them, and they are a PITA to R&R.

[Guenther]

insertdisk,

all good advice so far. I am curious, how did this all happen? Suddenly? Slowly? Some work done on the RT recently?

/Guenther

[MIAirhead]

The Idle use to once in a while run a little fast. Now after the first start of the day, which has a normal idle. Once you start to ride the idle goes up and stays up for the rest of the day. I did adjust the valves, it was starting hard. I still gets 40+ mpg, just idles fast. I don't drive in traffic very often, I guess I try and sync the carbs. but this would be my first try, so maybe the dealer for this.

[Guenther]

My guess would be the piston (1) in one carburetor is either stuck or, the diaphragm (13) is bad or, the spring (14) in that piston is bad. You can take the snorchel off the intake of the carburetor and check with your finger that you can easily push the piston up and you feel the resistance of the spring pushing it down.

http://www.realoem.com/bmw/showparts.do?model=0449&mospid=47888&btnr=13_0510&hg=13&fg=05

/Guenther

[amiles]

Methinks that you should invest in the carb manual from the Bing Agency. There is a peculiar situation like this that can occur when the idle circuit gets plugged up. Whatever happens the book will be of great value in days to come.

[MIAirhead]

:thumb To fix it the timing unit must be removed and serviced. Do NOT attempt to service it yourself. They are very delicate on the inside and parts are NOT available. If done wrong and damaged, new ones are over 500.00.

So I took of the unit and set to Oak today, when I get it back then I try the timing and carb procedure.

I hope it get back to install before Mini Rally.