R80 RT Hesitant mid range

[Darryl Flynn]

Hi, i have recently bought a 1990 R80 Rt that has covered 27k. The bike seems to start initially on only one cylinder and then after about 10 seconds the second one chimes in. After that it will start instantly and correctly BUT when riding it it seems hesitant and bogs down in the midrange but will accelerate hard and smoothly when asked to.
As a matter of course i have changed the diaphragms and changed the plugs for the recommended ones but no change.
Any ideas or advice would be appreciated. I can do most things myself but a pointer in the right direction would save a lot of time and effort.

Cheers Darryl

[Duane Ausherman]

Many use the term "bogged" but I never figured out what it meant. Elucidation would be nice.

[Darryl Flynn]

Many use the term "bogged" but I never figured out what it meant. Elucidation would be nice.

I use it to mean that the engine will not pick up cleanly and smoothly, ( A bit like trying to walk through a bog, ie you make progress but it's anything but clean and efficient )

Hope this Elucidation assists in your understanding of this term

[Manfred]

My '87 R80RT did that for a while. I replaced all the soft parts in my carbs, synchronized them, paid a shop to clean them good. My problem didn't go away until I replaced the coil. Starting issues and rough running at certain mid-range RPMs all vanished. YMMV

[SteveD]

My '87 R80RT did that for a while. I replaced all the soft parts in my carbs, synchronized them, paid a shop to clean them good. My problem didn't go away until I replaced the coil. Starting issues and rough running at certain mid-range RPMs all vanished. YMMV

I wonder, was 1990 pre or post the crack-o-matic dual coil? I'm guessing it was post. Still, could be the coil or something related.

[SteveD]

My '87 R80RT did that for a while. I replaced all the soft parts in my carbs, synchronized them, paid a shop to clean them good. My problem didn't go away until I replaced the coil. Starting issues and rough running at certain mid-range RPMs all vanished. YMMV

I wonder, was 1990 pre or post the crack-o-matic dual coil? I'm guessing it was post. Still, could be the coil or something related. Does it even have the original coil?

[SteveD]

My '87 R80RT did that for a while. I replaced all the soft parts in my carbs, synchronized them, paid a shop to clean them good. My problem didn't go away until I replaced the coil. Starting issues and rough running at certain mid-range RPMs all vanished. YMMV

I wonder, was 1990 pre or post the crack-o-matic dual coil? I'm guessing it was post. Still, could be the coil or something related. Does it even have the original coil?

"bogging" from carbs can happen just off idle if the transition holes below the butterfly are blocked, or it can happen at highway speeds if the floats are set too low. Recent threads have discussed such events.

T.t.triple post...d'oh! Sorry 'bout that.

[Duane Ausherman]

Many use the term "bogged" but I never figured out what it meant. Elucidation would be nice.

I use it to mean that the engine will not pick up cleanly and smoothly, ( A bit like trying to walk through a bog, ie you make progress but it's anything but clean and efficient )

Hope this Elucidation assists in your understanding of this term

That tells me more about the symptom you have.

There are many possible reasons for this to happen. I would start with a full service if you do your own work. Be sure to check compression too. Record everything that you find in your log book.

How new is the coil and wiring to the plugs? Have you run it in the dark to see if it has any ignition leaks jumping around?

An experienced BMW mechanic will often find something while doing the service, but certainly not always. Sometimes it is found only during the test ride. While the tester will usually get the clues to the cause, sometimes it is still not clear. Then it can require a bit of parts changing to find it, but that isn't common.

Usually I can ride a bike with some symptom and I first try the choke, or pull one throttle cable to try to isolate if it is only on one side, or both. I sit here trying to figure out how to describe it, but it is sort of a feeling that I would get that usually took me to the place. Not always, a few times a symptom would elude me and it just makes me tenacious.

Sometimes I would just go off the clock in order to investigate and FIX it.

Let us know what it is when you find it.

[Manfred]

My '87 R80RT did that for a while. I replaced all the soft parts in my carbs, synchronized them, paid a shop to clean them good. My problem didn't go away until I replaced the coil. Starting issues and rough running at certain mid-range RPMs all vanished. YMMV

I wonder, was 1990 pre or post the crack-o-matic dual coil? I'm guessing it was post. Still, could be the coil or something related. Does it even have the original coil?

"bogging" from carbs can happen just off idle if the transition holes below the butterfly are blocked, or it can happen at highway speeds if the floats are set too low. Recent threads have discussed such events.

T.t.triple post...d'oh! Sorry 'bout that.

My bike had a stock duel coil, I replaced it with an ACCEL 140403S Universal Super Coil Kit and it was a superb improvement!