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Rough Running


Dave58

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I have a 97 R1100RT with 22000 miles on it. Since I bought the bike used last year,(with 15K on it) I have had this problem that I have been trying to chase down.

The bike will run great for 3 or 4 rides of 45 miles, and then the next ride it will act up. On the next ride it will be fine.

When this happens the bike is warm and ridden at 75-80 MPH on the interstate. The engine will start to run rough over 4000 rpm, and causes a vibration. It feels like it's lost power. If I slow down to 65 and keep it under 4000 rpm it smooths out and seems fine. It is really noticable going up hill or into a head wind. If I throttle down it will backfire, and if I come to a stop off the interstate, many times the engine "pops" and dies when I pull the cluth in.

Sometimes If I shut the bike down for more than 5 minutes, and get going again, it will be fine at high speeds. If I don't go above 4000 RPM, this never happens.

I have replaced the fuel filter, spark plugs, adjusted the valves and TPS. The HALL sensor was tested at a dealer and was ok.

Anybody have any ideas?

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Sound like fuel starvation. Things to check;

 

1- Fuel filter.

2- Fuel quality.

3- Vacuum leaks at TBs.

4- Dirty injectors. Add Techron to your fuel.

5- Check ignition coils, plug wires for condition, cracks.

6- Check plugs for deposits, correct heat range, gap adjustment.

 

Report back here with results.

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I vote for a fuel problem... I think a venting problem may be crosed off the list by having another key in the gas cap and when it happens, crack the cap open and see it returns to normal. Or go for a ride with the gas cap down but not secured... I take no responsibility for complications doing this... But I can tell you (first hand) that you can ride for a while without the cap locked down.

 

Give it a try..

 

BK

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While I happen to think that Techron is a magic potion (that actually works for me), I had a similar problem with my tractor a few years back (a Wheel Horse, not a BMW tractor...). It would work fine until I hit a certain engine speed (with no tach, I have no idea what that was). It turns out it was a bad negative lead off the battery. After replacing the entire lead, I've not had the problem since. I would suggest you check your leads, also, note that (I just found this out) the negative cable on the RT has a multitude of smaller negative (ground) leads twisted into it (perhaps one bad lead?).

 

(My $.02, not sure if my tractor problem is even related)

 

Good Luck.

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I have a 97 R1100RT with 22000 miles on it. Since I bought the bike used last year,(with 15K on it) I have had this problem that I have been trying to chase down.

The bike will run great for 3 or 4 rides of 45 miles, and then the next ride it will act up. On the next ride it will be fine.

When this happens the bike is warm and ridden at 75-80 MPH on the interstate. The engine will start to run rough over 4000 rpm, and causes a vibration. It feels like it's lost power. If I slow down to 65 and keep it under 4000 rpm it smooths out and seems fine. It is really noticable going up hill or into a head wind. If I throttle down it will backfire, and if I come to a stop off the interstate, many times the engine "pops" and dies when I pull the cluth in.

Sometimes If I shut the bike down for more than 5 minutes, and get going again, it will be fine at high speeds. If I don't go above 4000 RPM, this never happens.

I have replaced the fuel filter, spark plugs, adjusted the valves and TPS. The HALL sensor was tested at a dealer and was ok.

Anybody have any ideas?

 

Sounds electrical to me. Electrical circuits are essentially "off/on" switches. As they wear, the circuit may close fine cold, but when the bike gets hotter, the switch expands. All of which is to say, your HES may test fine cold, but fail when at different temperatures. Same thing applies to your spark plug wires and coil. Test resistance cold and warm.

 

The RPM this occurs at may be a red herring. If either cylinder has a problem (electrical, mechanical, or fuel), it'll throw the engine out of balance (like misadjusted throttles). I'd check compression, check every electrical component warm (the general concensus is that the motronic almost never fails; wouldn't worry about that yet), then check fuel pressure. You could have a vacume leak at the throttle bodies.

 

It could be a fuel problem, but the "hot versus cold" and inconsistent good/poor performance makes me think something electrical is failing.

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Thanks for the input. The plug wires did ohm out, but I never tried it when the bike was warm. I was wondering about a bad coil too, but I was told by a BMW service manager that he's never seen one go bad. Maybe mine is the first?

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