BMW K bikes (Bricks)

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1Back to top Go down   Knock Knock from the engine Empty Knock Knock from the engine on Thu Jan 30, 2020 11:18 am

JGT

JGT
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Have already carried out a search on the Forum for this problem but this is somewhat different to anything I have read.
K75RT with 59000 miles on the clock. Starts and runs well. First 25 miles at speed engine quite. Stop and restart, light Knock as you blip the throttle.  From then on running at 70 MPH engine is growling, easing back throttle makes no difference until approx 55/60 is reached then goes quiet. The engine is very smooth at all times. Any suggestions guy's?


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1992 K75RT  1979 IZH Planeta3
    

2Back to top Go down   Knock Knock from the engine Empty Re: Knock Knock from the engine on Thu Jan 30, 2020 12:19 pm

92KK 84WW Olaf

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Sometimes injector issues can give a diesel knock.

Metallic knock......alternator bushes aka monkey nuts??


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1992 K100LT 0193214 Bertha Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red 578 bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 689 58,645 now 106,950 miles Deceased.
1983 K100RS 0011171 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 37,190 miles
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles.
    

3Back to top Go down   Knock Knock from the engine Empty Knock when hot on Thu Jan 30, 2020 1:34 pm

daveyson

daveyson
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Piston pin knock? 

Dunno if you can run a 75 on two cylinders.  If you can and it's louder at one cylinder, and unplugging its injector connection makes the sound go away,  that might give a hint. 

For sure it will vibrate like crazy (maybe even more noisy) don't try this unless you get some feedback that you can on a 75.


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11/1985 bmw k100rt (late model)  Vin. 0090567
    

4Back to top Go down   Knock Knock from the engine Empty Re: Knock Knock from the engine on Thu Jan 30, 2020 11:45 pm

Laitch

Laitch
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@JGT wrote:. . . From then on running at 70 MPH engine is growling . . .
You seem to indicate the engine and moto run well at all speeds regardless of knock or growl.

To me, a knock differs significantly in sound from a growl. It would be difficult for me to mistake the sound of a pileated woodpecker's excavating for the sound of a threatening bull mastiff.

Check that all fairing components, fenders and exhaust fittings are fastened securely. Check your oil levels—both transmission and engine. Try to make a video recording of the sound then post it on YouTube, or try to expand your description of the noise.


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1995 K75 81,000 miles
Knock Knock from the engine Usa-lo10
    

5Back to top Go down   Knock Knock from the engine Empty Re: Knock Knock from the engine on Fri Jan 31, 2020 5:13 am

JGT

JGT
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Interesting point about the injection because once warm the the idle is not constant and the revs float slightly.
As for the noise, at 5000 rpm plus the knock is just a constant rough sound only disappearing as the revs drop corresponding to the lower speed. The engine is by far and away the smoothest of the 3 K75's I have owned.


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1992 K75RT  1979 IZH Planeta3
    

6Back to top Go down   Knock Knock from the engine Empty Re: Knock Knock from the engine on Sat Feb 01, 2020 9:59 am

tinyspuds

tinyspuds
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My 100 with similar mileage started to sound like the small end bearings were shot after a 300 mile run. a loud clatter/rattle at tickover.
I had the injectors cleaned plus new pintles and rings, all sorted.


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1985 BMW K100RT + Hedingham HUB and LL’s. VIN 0028106. (Not blind to the irony of an April 1 production date).
1954 Royal Enfield 350 Bullet. Original.
    

7Back to top Go down   Knock Knock from the engine Empty Re: Knock Knock from the engine on Sat Feb 01, 2020 1:13 pm

JGT

JGT
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More miles added today and bike improving considerably. The rough sound at speed seems to be decreasing as does the knock when bliping the throttle. Looking back through the records that came with the bike, in the last 7 years it was only averaging 450 mile/year.  I'm beginning to think the fuel injection system is a little gummed up. The fuel filter has a 2008 date on it. A trip to Motobins in order I think.


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1992 K75RT  1979 IZH Planeta3
    

8Back to top Go down   Knock Knock from the engine Empty Re: Knock Knock from the engine on Sat Feb 01, 2020 2:35 pm

Point-Seven-five

Point-Seven-five
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These bikes really don't like being idle.  One thing I found with my K75RT was that between 1200 and 2000 rpm a bit of roughness causes a clank from the engine.  Turns out the drive for the balance shaft has a bunch of slop machined into it.  Any variation in the firing between cylinders will make it bang around in the slot.Knock Knock from the engine Dscn1710


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Present:
1994 K75RT
1991 K100RS
1988 K100RS SE

Past:
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

9Back to top Go down   Knock Knock from the engine Empty Re: Knock Knock from the engine on Sun Feb 02, 2020 4:31 am

JGT

JGT
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Gold member
Have made a manometer to check throttle body balance and will also check air leaks with the carb cleaner spray trick.


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1992 K75RT  1979 IZH Planeta3
    

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