BMW K bikes (Bricks)

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1Back to top Go down   Rough when warm Empty Rough when warm Sun Aug 06, 2017 9:57 am

timo27

timo27
Silver member
Silver member
Hi all. i've just about got the k100 (1984) running nice, however after about four miles or when warmed up she starts to run like a bag of poo any ideas, new (second hand injectors and coils) new plugs new leads new fuel filter and pump new crank case breather new air filter new vac and fuel pipes.

    

2Back to top Go down   Rough when warm Empty Re: Rough when warm Sun Aug 06, 2017 10:39 am

duck

duck
Life time member
Life time member
My guess:Air leaks (cracks) in the boots between the TBs and cylinder head.


__________________________________________________
Current stable:
86 Custom K100 (standard fairing, K75 Belly pan, Ceramic chromed engine covers, paralever)
K75 Frankenbrick (Paralever, K11 front end, hybrid ABS, K1100RS fairing, radial tires)
86 K75C Turbo w/ paralever
94 K1100RS
93 K1100LT (x2)
91 K1
93 K75S (K11 front end)
91 K75S (K1 front end)
14 Yamaha WR250R
98 Taxi Cab K1200RS
14 K1600GT
http://www.ClassicKBikes.com
    

3Back to top Go down   Rough when warm Empty Re: Rough when warm Sun Aug 06, 2017 10:39 am

RicK G

RicK G
admin
admin
Have you been through all the intake tract. These bikes are getting old and leaks will happen and when warm will run badly.
Check and make sure all the clamps are tight and the manifold stubs are sealed. Anywhere that air can leak into the inlet from head to air filter. Because the air is measured just after the filter anything that gets in after there will make a big difference to the mixture ratio. Also check the Z shaped rubber tube from the rear of the plenum chamber to the engine. It will leak a heap of air if perished.
If you have already done all of this you may need to check out the temp sensor for correct readings.


__________________________________________________
"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama


Bikes 2004 K1200GT 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki
    

4Back to top Go down   Rough when warm Empty Re: Rough when warm Sun Aug 06, 2017 9:11 pm

Dai

Dai
Life time member
Life time member
What Rick says. Spray WD40 or similar around the injector body rubbers when the engine's running. Any rise in revs indicates a leak. For the price or new ones (top and bottom), I wouldn't even consider buying secondhand because you have no idea how old they are, how they've been looked after and if they have unseen cracks in them. Help the lower rubbers to seal to the cylinder head properly with a bit of Threebond (expensive but when you've used it once you'll never go back to ordinary gasket cement again). I treated LFB to a new set of rubbers after I got just a bit p!ssed off when she dropped to 2.5 cylinders in the Welsh mountains on the first day of a four day run. Unbelievable difference...


__________________________________________________
1983 K100 upgraded to K100RS spec, 1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

5Back to top Go down   Rough when warm Empty Re: Rough when warm Sun Aug 06, 2017 9:59 pm

RicK G

RicK G
admin
admin
One place to check is just above and below the clamps, the rubbers tend to split there and it's not till you remove the throttle bodies that it becomes evident. Also check the O-rings on the injectors they can leak air when old


__________________________________________________
"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama


Bikes 2004 K1200GT 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki
    

6Back to top Go down   Rough when warm Empty Re: Rough when warm Sun Aug 06, 2017 10:43 pm

duck

duck
Life time member
Life time member
@Dai wrote:What Rick says. Spray WD40 or similar around the injector body rubbers when the engine's running. Any rise in revs indicates a leak. For the price or new ones (top and bottom), I wouldn't even consider buying secondhand because you have no idea how old they are, how they've been looked after and if they have unseen cracks in them. Help the lower rubbers to seal to the cylinder head properly with a bit of Threebond (expensive but when you've used it once you'll never go back to ordinary gasket cement again). I treated LFB to a new set of rubbers after I got just a bit p!ssed off when she dropped to 2.5 cylinders in the Welsh mountains on the first day of a four day run. Unbelievable difference...

Despite what the can says, WD40 is no longer flammable like it used to be. (Thank the safety Nazis for that one.)

I use starter fluid although I've heard of others using propane or other flammable gasses.

You can also spray some water mist and if the RPMs go down then that indicates you've got an air leak.


__________________________________________________
Current stable:
86 Custom K100 (standard fairing, K75 Belly pan, Ceramic chromed engine covers, paralever)
K75 Frankenbrick (Paralever, K11 front end, hybrid ABS, K1100RS fairing, radial tires)
86 K75C Turbo w/ paralever
94 K1100RS
93 K1100LT (x2)
91 K1
93 K75S (K11 front end)
91 K75S (K1 front end)
14 Yamaha WR250R
98 Taxi Cab K1200RS
14 K1600GT
http://www.ClassicKBikes.com
    

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