BMW R1200R R1150R/T F800 K1200R R1100R/T R1250R RnineT Message Board

Help! Lately I've been experiencing some sort of surging from my bike at about 5000 rpms. The tach bounces up and down and the bike bucks until I either shift or accelerate above 5500 rpms or decelerate below 4900 rpms. It happens in all gears and is quite annoying. I've heard or surging, but all the other stories I've heard of the surging take place at about 3000 rpms. Is this the same surging or do I have some other new problem? My bike has 18000 miles on it and was just tuned up a few months ago. It's never done this before. I did just have my rear bearing replaced, but I can't imagine the two events are related. I am getting sick of taking my bike into the shop all the time though. Any help would be appreciated!

Don't know that I can help much here, but the tach bouncing around could indicate a Hall Effect (timing) Sensor problem, but not sure why it would happen only at that rpm... Maybe somebody else has had this happen and got it figured out. Good Luck!

it could be the HALL sensor or a bad coil. Ensure that the coil packs are not cracked; a spark plug wire may have came loose. You could also have a vacuum leak around the TB.

You'll get better guesses if you tell us more about your ride.

ProductUser

sorry, I have a 2004 r1150r , with 18000 miles. It had its annual tuneup about three months ago. After the tuneup I did have a problem with the bike occasionally dying at intersections, but the dealer checked it out and said the idle was just set to low so they dialed it up. It's a daily commuter and I don't ride crazy or anything. I just got the bike back from the dealer after being there for two weeks (!) for a rear bearing replacement. Before the rear bearing replacement there was no problem with surging. I don't know if any of this helps, but if if anyone has any ideas I'd appreciate it! It's going to be embarrassing explaining to my girlfriend how my "reliable and tough" BMW is headed back into the shop for the fourth time this year.

Since it's a 2004, I would rule out the Hall sensor. I would make sure the spark plug wires are very secure. You may still have a bad coil, but check the easy stuff first.

PU

I jiggled the plugs and they seem firm. If the plugs are loose, would that cause the engine to only surge at certain RPMs? It seems like loose plugs would affect the engine at all RPMs.

Air leaks?

Sounds like an ignition problem to me. In olden times when cars had points if over reved the points would "flote" that is not fallow the distributor cam, that would make the tach bounce alover the place.

Good Luck

I don't know if was on this board or on another BMW forum, but one person discovered that one of the coil packs was bad, despite the low mileage. The symptoms were similar to yours. He was able to isolate which side was bad, however, which enabled him to discovered the bad coil pack.

Don't jiggle the wires; pull them out and reseat them (use the little plastic tool in your tool kit to removed the plug wires). Also, check for any chafed plug wires that may cause the spark to jump during high RPM's. Ensure the coil packs are not cracked, either.

If you fill out your profile, there may be someone on the board that may be able to come out and help. Otherwise, you may just have to take it to he dealer.

PU

thanks for the helpful responses. I took out the spark plugs, they look fine and were seated pretty well. I think I cracked one of the rubber gaskets on the coil while taking out the plug, but I don't see how that might affect things. When you say the "coil pack" do you mean the coil that slides right over the plugs, or is there another coil?

seisouso --

What you described as your issue appears to point to some sort of electrical issue during high RPM's. During high RPM's, the coil packs are charged and discharged at very high rates. If they are cracked or bad, they will cause a missfire during high RPM's. This is why you are not seeing any issues at lower RPM's.

Again, it's hard to diagnose problems through the net. At this point, it may be advantageous to take your bike to the dealer or a capable BMW mechanic. Sorry.

PU

I'll be taking her in on Thursday. Damn, I was hoping for a simpler (and cheaper) solution. No chance it's just the charcoal canister? Oh well, thanks a bunch guys.

The tach bounces up and down . . .

seisouso, THAT statement is a HUGE clue as to what is wrong. I agree with all of ProductUser's answers about it being electrical and the ignition the most likely. The sources to check are:

-- Cracked, poorly grounded or defective coil
-- Faulty Hall sensor, shorted lead wire or connection to the Motronic
-- Fuse partially melted or it's female terminals weak or corroded
-- Loose battery Pos or Neg connection point - - - at both ends
-- Burned or corroded ignition keyswitch contacts.
-- Burned relay contacts or heat damaged internal return spring
-- Oh NO! Damaged Motronic computer

Quck/Easy fixes are:
-- swap the 4 small black identical relays with each other.
-- check the connections mentioned above
-- reset the Motronic by #5 fuse removal procedure.

I took the bike in to Honda Hollywood which is the closest BMW dealership to me, and the morons at the service department kept the bike for a week and then told me there was nothing wrong with it. They said they test rode it and couldn't find any problems and that they hooked it up to their diagnostic computer and nothing came up. So I thought that maybe the problem went away and rode it home. Of course, the problem is still there and I'm baffled as to how they didn't notice it when they test rode it, as it was very apparent. The only thing I can think of is that they may have just been redlining it on the test ride, and if you just power right through the 5k rpm zone the engine problems may not be as easy to detect. In any case, they mechanics there are either very sloppy or are way too rushed as they also deal with all of LAPD's bikes too. Whatever the case, I won't be going back there again and for anyone who lives in Los Angeles I recommend the same.

Sorry for this naive question, but :
Where on the bike are those coil packs that I should check ?

Below is a link to a post that resulted in the coil packs being bad. His description of the problem differs, but this is just an example of how something can look good, yet actually be bad.

Coil Pack Issue

ProductUser

stratus17 wrote:Sorry for this naive question, but :
Where on the bike are those coil packs that I should check ?

When you remove the primary spark plug wire with the special tool, you're actually removing the coil pack. Yes, the coil pack sits on top of the primary plug.

The coil pack for the secondary plug (you may not have one) is located externally; it is NOT attached to the plug like the primary coil.

ProductUser

you checked your throttle cables?...

just a thought.

ProductUser wrote: When you remove the primary spark plug wire with the special tool, you're actually removing the coil pack. Yes, the coil pack sits on top of the primary plug.

The coil pack for the secondary plug (you may not have one) is located externally; it is NOT attached to the plug like the primary coil.

ProductUser

Thanks, ProductUser.