Author Topic: K75 - chugging at low throttle  (Read 810 times)

Offline Vlad

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K75 - chugging at low throttle
« on: March 13, 2018, 03:08:53 PM »
Hi everyone. Wondering if anyone has some ideas for this issue. I just started the bike up again after being mostly sitting for the winter. (I had started it a few times here and here to test out new additions and what not, and it ended up killing the battery, but thatís fixed now after it was left on a trickle charger for a few days)


I insured the bike yesterday, changed the engine oil, transmission oil, and final drive oil and took it out for a ride. I also checked the spark plugs and they seem to be in good condition.


What I noticed after a few minutes was it it was chugging at low throttle input. As soon as I pulled a little heavier on the throttle, the chugging went away. It rode the bike for an hour, and the chugging seemed to improve over the durations of the ride. When I was on my way home, it was barely doing it.. but there still is something off, it feels like it hesitateds to give more gas when you first start slowly pulling the throttle. Although at the beginning of the ride I was quite worried because the engine chugging was quite pronounced.
I put some new gas in there and it is doing the same thing.


Any idea what might cause this sort of issue?


Thanks!
  • Victoria, BC
  • 1993 K75RT

Offline Chaos

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Re: K75 - chugging at low throttle
« Reply #1 on: March 13, 2018, 04:16:45 PM »
not sure what "chugging" might be, hesitation or slight miss?   I had similar issues years ago, turned out to be water settled at the bottom of the gas tank, a can of HEET gas dryer took care of it.  Or run some Techron fuel injector cleaner through it.  Check the little crankcase ventilation z hose and the throttle body rubbers, could be a vacuum leak. Just guessing but those a some common problems.
  • sw ohio
1987 K75S    VIN 0231
Original owner, Original litter
200,000 miles (plus or minus) and 5 paint jobs
2012 Ural 2WD sidecar (BMW's bastard step child)

Offline beemuker

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Re: K75 - chugging at low throttle
« Reply #2 on: March 13, 2018, 04:17:37 PM »
how many rpm's before the "chugging" goes away. mine kind of rattles a little at low rpm's. I'm on my 3rd K75, and I think they all did that. I could be wrong. BUT, these bikes love to rev.
  • Panama City, FL
  • 94 K75s , Dakar yellow ABS

Offline Vlad

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Re: K75 - chugging at low throttle
« Reply #3 on: March 13, 2018, 06:07:00 PM »
Very low rpm probably under 2000. By chugging i just mean the power cuts out and comes back repeatedly at low throttle
  • Victoria, BC
  • 1993 K75RT

Offline rbm

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Re: K75 - chugging at low throttle
« Reply #4 on: March 13, 2018, 06:07:47 PM »
I've put 2 + 2 together and found the problem is the insurance.  Remove the insurance and the chugging will stop.  :hehehe

Seriously though, I think is might also be injector related.  Did you run fuel stabilizer through the system before you stored it for the winter?
  • Regards, Robert
Toronto, Ontario

1987 K75 - Build Blog @http://k75retro.blogspot.ca/

Offline beemuker

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Re: K75 - chugging at low throttle
« Reply #5 on: March 13, 2018, 06:10:10 PM »
Very low rpm probably under 2000. By chugging i just mean the power cuts out and comes back repeatedly at low throttle
ok, that's not normal
  • Panama City, FL
  • 94 K75s , Dakar yellow ABS

Offline Vlad

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Re: K75 - chugging at low throttle
« Reply #6 on: March 13, 2018, 06:42:47 PM »
Haha.. no I havenít put anything but gas in it. Is there some sort of additive I should be putting in there?
  • Victoria, BC
  • 1993 K75RT

Offline beemuker

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  • Posts: 431
Re: K75 - chugging at low throttle
« Reply #7 on: March 13, 2018, 08:18:34 PM »
Haha.. no I havenít put anything but gas in it. Is there some sort of additive I should be putting in there?
yea, if you are having issues, see chaos post above.
  • Panama City, FL
  • 94 K75s , Dakar yellow ABS

Offline lmiklosy

  • One Less Car
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Re: K75 - chugging at low throttle
« Reply #8 on: March 13, 2018, 11:14:02 PM »
Remember the Bosch fuel controller will cut-out the fuel supply to the injectors when two conditions are met:  the engine speed exceeds 2000 rpm and the throttle valve switch is closed. When the engine speed falls below 2000 the controller activates the injectors again. If the idle speed is set too high or the fast-idle lever is left on you might feel a chug-a-lug as the engine speed passes through 2000 rpm.  There's a discussion about this elsewhere at Motobrick, look-up "back-firing".      Does that help?
  • Laguna Beach, CA
  • 1993 K75S-Mystic, 1981 R100RS-RedBaron, 1991 K75S-Marrakesh

Offline blackie1

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  • christchurch nz
Re: K75 - chugging at low throttle
« Reply #9 on: March 14, 2018, 01:02:25 AM »
i'd be giving it a bloody good thrashing to blow out the cobwebs.
  • new zealand , where else would u want to live, really
  • 1991 K75RT naked 40,000kms

Offline richarddacat

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K75 - chugging at low throttle
« Reply #10 on: March 14, 2018, 02:12:28 AM »
Haha.. no I havenít put anything but gas in it. Is there some sort of additive I should be putting in there?
Fuels today will evaporate if additives are not added.
Personally Iíll fill up with non-ethanol and even add Sea Foam or another additive. I do that with all engines that sit through the winter. I donít have spring starting or running issues as a result.

Sometimes itís best to drain your tank and refill with fresh fuel.

Definitely run non-ethanol in your lawn equipment year around and that will save some headaches as the years pass.

Thatís my two cents.
loud pipes annoy people, well designed helmets save lives.

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