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BMW R100GS - A Bit rough ?? Or just Mine. BMW R100GS - A Bit rough ?? Or just Mine.
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  #1  
Old 26 Feb 2008
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BMW R100GS - A Bit rough ?? Or just Mine.
Hello all,

I'm totally new to airheads and getting on my newly acquired 1988 r100gs its very different to my last bike. I'm getting a fair amount of vibration, not excessively, but certainly noticeably, particularly when travelling at a steady speed, it smoothes out when accelerating. Being completely new to old bmw's, and this bike being new to me, I'm unsure if I should be concerned or if this is just part of the ride. Obviously its hard for people to tell without having a test ride but what are other peoples experiences of their airheads? Are they all a bit rough??

Any opinions appreciated.
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Old 26 Feb 2008
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Talking Should be smooth(ish)
Quick stab... carb balance. But you cant do that until everything else is in order... tappets, timing, plugs, clean carbs etc & a warm engine

John
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Old 27 Feb 2008
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Talking Not a jap bike ;-)
The old GS isn't a Japanese bike for sure, but above 3000 revs it should smoothe out. If the vibrations are still more than you appreciate after following John's advice, all that remains is to have the engine balanced. That's what I did. Well, it doesn't run as smooth as a turbine, but noticeably better than before. Besides that I believe that everything should last longer due to reduced vibrations.

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Old 28 Feb 2008
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Diaphragms
If the bike runs rough after normal servicing, you could check that the throttle cables are seated in the adjuster ferrules, and if that is ok, have a look at the carb diaphragms. If one is split or leaking, it will upset things.
cheap and easy to repair.
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Old 28 Feb 2008
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Quote:
Originally Posted by Bin Ridin View Post
If the bike runs rough after normal servicing, you could check that the throttle cables are seated in the adjuster ferrules, and if that is ok, have a look at the carb diaphragms. If one is split or leaking, it will upset things.
cheap and easy to repair.
This is good advice. Personally i would do a major ( annual) service plus install new needles and needle jets. It will cost less than £10 for teh parts and can save a lot of problems. These bikes should not be difficult to adjust the running to be reasonably smooth ( For a TWIN), if it is difficult, something else is wrong (diaphragms suspect no. 1 ).

sychronise the carbs by eye, then road test. Run at the speed and throttle opening you will be spending most time at. Then adjust one of teh carbs cables a small amount. retest. if smoother repeat. If rougher adjust cable other way . and retest. Eventually you will dertermine best place. It may not be as good at other rpms or throttle openings. but that is teh best you can do, live with it.
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Old 29 Feb 2008
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Shaky shaky
Quincy,

Redboots had good advice about making sure everything else is OK before doing too much to the carbs. They may well be the problem but you will never get them adjusted correctly if something else is off. You were on the right track starting with your valve adjustment as I saw in an earlier post from you. Same advice as before from me. Go to Robert Fleischers site index BMW Airhead Motorcycle Repairs and scroll down to article 7A. It's about carb adjustment but he tells you what to fix first. Articles on the other stuff are there as well... like throttle cable adjusting procedures as suggested by others. Crank up your printer and make yourself a binder of useful stuff. Makes for great bathroom reading.
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Old 29 Feb 2008
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Originally Posted by Sam I Am View Post
Quincy,

...
Go to Robert Fleischers site index BMW Airhead Motorcycle Repairs and scroll down to article 7A. It's about carb adjustment but he tells you what to fix first. Articles on the other stuff are there as well... like throttle cable adjusting procedures as suggested by others.
...

That's an interesting site. Good stuff.
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Old 18 Mar 2008
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Rough 88' R100GS
The above advice is all good. Your bike should have a nice smooth spot around 4000rpm. I've heard that there is quite a variance in the smoothness of the (particularly 1000cc) airhead engines due to imperfect balance at time of manufacture.

However, the type of roughness you are talking about is almost certainly due to improper tune, or something else out of whack. As mentioned above I'd check the throttle and choke cables first. Several times I've had these come out of their sleeves at the junction under the tank. It throws the engine out of balance and makes tuning impossible.
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Old 21 Mar 2008
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Doh! i ain't no mechanic, but-I bought a 88 100GS last may (1200 miles on it- long story)...runs great, cept no taillight, speedolight or parklight. All one fused circuit, and I'm workin on it...have you checked the fork tubes for alignment? Hate to bring this up, but its easy to check with a caliper or somesuch- should be equidistant movin up the fork...there's more info at the airhead website (ABC).
again, ain't no mech, but if the carbs are good, I'd also check the forks. Oh, and i ran some SEAFOAM in my gas for a couple of weeks, and it cleaned them carb innards real good.
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