Taking ‘93 RS for first decent ride. The bike is now idling at 2,000 rpm when warm. It didn’t do that on prior short trips around the section. Also, as I just pulled in and turned it off, it will not light up…all went dead. Checking fuses first. What might cause the idle to suddenly increase? When flipping the throttle to get it to then drop it will set at a higher rpm. Cables are looking okay, starts fine and idles fine initially. Appreciate any input. And for the life of me not sure where you’d connect tubes to balance carbs as there are no visible ports to access. Valves are set correctly, new plugs, new air filter…what the….?
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Help! Double Dip
- Thread starter motodan
- Start date
Check for air leaks downstream of the carb, the rubber inlet tubes to the heads. Spray some brake cleaner around the carb while running to see if there's an RPM change. I'm not totally familiar with the late model Airheads with the electronic ignition, but I believe there are still a set of fly weights in the bean can which regulate the advance. When the RPM is hanging, shift into 1st gear and slowly let out the clutch lever to drag the RPM down. Does the RPM stay down when you shift back to neutral? If so, that could be the advance weights sticking open.
Bike not starting...no sounds at all, no clicking or anything? First be sure the kill switch didn't get pushed. Check to be sure you have solid connections on the battery cables. Could the issue is the starter relay under the tank. The spade terminals can get corroded. You'll need to find the relay...about a 1" x 1" cube on the left side of the frame IIRC. Pull the relay out of the socket and push it back in a few times...could help to break the corrosion.
Bike not starting...no sounds at all, no clicking or anything? First be sure the kill switch didn't get pushed. Check to be sure you have solid connections on the battery cables. Could the issue is the starter relay under the tank. The spade terminals can get corroded. You'll need to find the relay...about a 1" x 1" cube on the left side of the frame IIRC. Pull the relay out of the socket and push it back in a few times...could help to break the corrosion.
Well, manual says there’s 2- 8 Amp fuses, however there are 3 - 15 amp fuses and they’re all good. Bike is dead as a door mail and battery is fully charged. The RT is in the corner laughing at me.
Okay, easy first, clean battery connections first and fired right up. Only 20 minutes since ride. Let warm up a little and now tach showing normal response. I will go back out to see if It will hang up around 2,000 again. However, if a little cool down get it back to correct idle…is there a more specific problem? I bought this for “something to do”, looks like that’s working out. �� Out and back and back to 2,000 rpm idle. Letting clutch out a tad to drag rpm down, has it going right back up when pulled back in. Found no increase in rpm with cleaner spray. Tightened all carb hoses.
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88bmwjeff
SF Bay Area
As far as where to connect the tubes to balance the carbs, the ports should be located at the bottom of the carbs adjacent to the idling mixture screw. It's been a while, but I think BMW had both carbs linked via a tube to balance the pressure between them. If your bike still has this tube, then you would have to remove it first.
stevenrankin
Active member
Check
As Kurt suggested, check for a vacuum leak downstream of the carbs.
On this bike, the one into two throttle cable could be hanging up. Check the cable action to make sure it is adjusted properly and operates as it should.
Also check your choke cables and make sure the choke is off when it should be.
Last thing to do is to perhaps readjust idle speed after a very long warm up ride. My RT hates having the idle speed adjusted after any ride less than 25 miles. I mean it HAS to be warmed up for me to get the idle right. My adjusting idle at anything less than really warm leads to a high rpm idle later on.
As for the bean can, that would be the last thing to check, honestly if you have a huge amount of miles on the bike or it has been sitting a long time, the bean can weights can perhaps hang up. This however is not been a real big issue with the system. Sure, a few people have had issues but more problems are caused by the above carb and cable stuff than hanging advance weights.
Good luck. St.
As Kurt suggested, check for a vacuum leak downstream of the carbs.
On this bike, the one into two throttle cable could be hanging up. Check the cable action to make sure it is adjusted properly and operates as it should.
Also check your choke cables and make sure the choke is off when it should be.
Last thing to do is to perhaps readjust idle speed after a very long warm up ride. My RT hates having the idle speed adjusted after any ride less than 25 miles. I mean it HAS to be warmed up for me to get the idle right. My adjusting idle at anything less than really warm leads to a high rpm idle later on.
As for the bean can, that would be the last thing to check, honestly if you have a huge amount of miles on the bike or it has been sitting a long time, the bean can weights can perhaps hang up. This however is not been a real big issue with the system. Sure, a few people have had issues but more problems are caused by the above carb and cable stuff than hanging advance weights.
Good luck. St.
m_stock10506
Well-known member
All excellent suggestions for you to check. I would add that it is important that when you adjust the carbs, you have to ride the bike first and thoroughly warm it up. If the carbs are set up before the motor is warm, they will idle high once it gets to operating temperature.
pglaves
#13338
My experience with fast idle on Airheads is that there are two basic causes: 1) an air leak downstream from the throttle plate or slide; and 2) ignition advance mechanisms sticking. And generally if you load the engine to pull the rpm down and it stays down it is usually the ignition advance, but if the idle speed goes back up it is generally an air leak. The usual suspect is where the carburetor attaches to the head: either at the rubber sleeve or the flange to head connection. Other suspects are throttle shaft O rings as well as O rings on any of the adjusting screws.
The "motto" of the Airheads Beemer Club is "Simple by Choice". I think that pretty much answers your question!
stevenrankin
Active member
Miles and condition?
Given I don't know the mileage of the bike in question, I can't argue a whole lot about sticking advance weights other than to give my experience with the BMW electronic ignition bean can as well as observations from other bikes coming into my friend's airhead shop. I rode 200K miles on my original ignition system on my 84 RT, same bean can, before I fell prey to the hype of the "improved" performance of the Alpha replacement system and switched over. I still have the perfectly functioning bean can in my tool box as a spare.
The only time I ever see advance weights hanging up on any bike points or electronic is when there is either extreme wear or improper storage during a long period. Hey, I know there are flukes that can happen in all mechanical things, it is possible in this case but more than likely can be ruled out unless the owner tells us he has 100K plus miles on the bike or it has been sitting for 10 years. I won't even rule out an improper installation of the weights by BMW at the factory, things happen.
Very likely, the problem you are having is as stated, a vacuum leak and I am sorry, but unless you have a lot of miles I really don't believe the butterfly shaft is leaking.
I have adjusted a lot of Bing carbs in my time and all of them change Idle speed if they are not adjusted at the temperature they want to be adjusted at. LOL, I know they are not alive but sometimes I think they are possessed. I can ride my RS around a two mile run, adjust the carbs and they stay, the RT is different as I said.
Getting back to mileage, when was the last time the carbs were even rebuilt if ever? Perhaps it is time now? Without the bike in front of me, I expect a certain number of things to make sense based on what I know, and have experienced. If you are near me in Rochester NY, you can swing by or go out to Niagara County to my friend's shop. I don't charge, and he is reasonable with his costs. Oh, maybe a lunch in my case, LOL. St.
Given I don't know the mileage of the bike in question, I can't argue a whole lot about sticking advance weights other than to give my experience with the BMW electronic ignition bean can as well as observations from other bikes coming into my friend's airhead shop. I rode 200K miles on my original ignition system on my 84 RT, same bean can, before I fell prey to the hype of the "improved" performance of the Alpha replacement system and switched over. I still have the perfectly functioning bean can in my tool box as a spare.
The only time I ever see advance weights hanging up on any bike points or electronic is when there is either extreme wear or improper storage during a long period. Hey, I know there are flukes that can happen in all mechanical things, it is possible in this case but more than likely can be ruled out unless the owner tells us he has 100K plus miles on the bike or it has been sitting for 10 years. I won't even rule out an improper installation of the weights by BMW at the factory, things happen.
Very likely, the problem you are having is as stated, a vacuum leak and I am sorry, but unless you have a lot of miles I really don't believe the butterfly shaft is leaking.
I have adjusted a lot of Bing carbs in my time and all of them change Idle speed if they are not adjusted at the temperature they want to be adjusted at. LOL, I know they are not alive but sometimes I think they are possessed. I can ride my RS around a two mile run, adjust the carbs and they stay, the RT is different as I said.
Getting back to mileage, when was the last time the carbs were even rebuilt if ever? Perhaps it is time now? Without the bike in front of me, I expect a certain number of things to make sense based on what I know, and have experienced. If you are near me in Rochester NY, you can swing by or go out to Niagara County to my friend's shop. I don't charge, and he is reasonable with his costs. Oh, maybe a lunch in my case, LOL. St.
Thanks! First time I ever wished I lived closer to Rochester. �� I just purchased this bike, looks very well cared for. It has only 23,000 miles. It’s prior life was at a higher altitude (based in Spokane, WA). It is now in northern Indiana. I’ve had it just over two weeks. The first two around the section rides it showed no strange idle changes. The last two outings (20 and today 40 miles) ended in this elevated rpm mode. The valves are right on. Plugs are new, same for air filter. I’ve wanted to get it to a dealer just for the carbs even before this started. Michigan dealer didn’t seem interested in checking the balance, let alone a “problem”. Going to check with a couple of other dealers tomorrow, each 150+ miles away. And all cables seem to be properly adjusted.
Attachments
akbeemer
SURVIVOR
The "motto" of the Airheads Beemer Club is "Simple by Choice". I think that pretty much answers your question!
Ya, lost my head.
stevenrankin
Active member
Well
Well, I would rule out any kind of wear in the advance system or the butterfly. Vacuum leak or just not warmed up enough. I ended up buying a sync tool because I can no longer hear the change when adjusting carbs. I haven't used it much as really once carbs are set they don't change much. Oh cables wear and stretch but the carbs themselves don't. Good luck. St.
One other thing to check is the danged air injection system for the EPA requirements. I am sorry, I am not aware of what was added to bikes after 84, but a whole lot more was put on the bikes to clean up emissions after then. There is a chance perhaps one of the added hoses may be leaking a vacuum leak.
I wish I could be more help with pointing you in a particular direction to look on the air injections system and other EPA stuff. I don't know just how much information is available online or in any of the repair manuals.
I can tell you I took all of the air injection stuff off of my 84 and plugged the holes. A month or two later, the idle went crazy and the bike ran poorly. It turns out, I didn't use the correct amount of lock tight on the plug bolt into the port on the cylinder head and there was, you guessed it, a vacuum leak. Removal and proper loc fighting the plug solved the problem. St.
Well, I would rule out any kind of wear in the advance system or the butterfly. Vacuum leak or just not warmed up enough. I ended up buying a sync tool because I can no longer hear the change when adjusting carbs. I haven't used it much as really once carbs are set they don't change much. Oh cables wear and stretch but the carbs themselves don't. Good luck. St.
One other thing to check is the danged air injection system for the EPA requirements. I am sorry, I am not aware of what was added to bikes after 84, but a whole lot more was put on the bikes to clean up emissions after then. There is a chance perhaps one of the added hoses may be leaking a vacuum leak.
I wish I could be more help with pointing you in a particular direction to look on the air injections system and other EPA stuff. I don't know just how much information is available online or in any of the repair manuals.
I can tell you I took all of the air injection stuff off of my 84 and plugged the holes. A month or two later, the idle went crazy and the bike ran poorly. It turns out, I didn't use the correct amount of lock tight on the plug bolt into the port on the cylinder head and there was, you guessed it, a vacuum leak. Removal and proper loc fighting the plug solved the problem. St.
Sure, choke is closed.
Check your work as well
In another thread you mention taking the gas tank off. You should check the reinstallation of the tank to make sure you put stress / pressure on any of the throttle cables or reroute them in a way that they might bind up. The cables themselves could be compromised also so check them carefully.
You might also check the carb jetting to make sure its appropriate the altitude in your area, you did mention the bike came from a higher altitude with that it may have had alterations made in the jetting and needle setting to make it run correctly at the higher altitude.
In another thread you mention taking the gas tank off. You should check the reinstallation of the tank to make sure you put stress / pressure on any of the throttle cables or reroute them in a way that they might bind up. The cables themselves could be compromised also so check them carefully.
You might also check the carb jetting to make sure its appropriate the altitude in your area, you did mention the bike came from a higher altitude with that it may have had alterations made in the jetting and needle setting to make it run correctly at the higher altitude.
Appreciate everyone's input. Appears the high idle is solved. Had a MOA PM me, we discussed the issue and eventually found the simplest adjustment was the difference. Yes, I found that embarrassing however, thought closure was my duty. Let me defend myself by stating my first couple of shorter outings, on this new to me '93 RS, did not end in an abnormal high idle. The next two longer rides did. Sorting out the idle screws after a very complete warmup was the simple cure.
