BMW K bikes (Bricks)

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1Back to top Go down   Pops and backfire Empty Pops and backfire on Sun Jan 05, 2020 1:34 pm

BooG

BooG
Platinum member
Platinum member
The K75S has become a little hard to start of late, and also has developed a farting problem on deceleration. I have checked TPS and I can hear a click from it when the throttle is turned. The exhaust joint seems OK also.
What else might be responsible...air intakes possibly?

    

2Back to top Go down   Pops and backfire Empty Re: Pops and backfire on Sun Jan 05, 2020 1:54 pm

Dai

Dai
Life time member
Life time member
Easy bits first: Z-tube from the plenum chamber to the crankcase is split; one or more vacuum intake caps missing from the throttle bodies.


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'83 K100 upgraded to K100RS spec, '87 K100RT
Others...
'78 Moto Guzzi 850-T3, '79 Moto Guzzi 850-T3 California,'93 Moto Guzzi 1100ie California
    

3Back to top Go down   Pops and backfire Empty Re: Pops and backfire on Sun Jan 05, 2020 3:18 pm

Point-Seven-five

Point-Seven-five
Life time member
Life time member
Adjusting the TPS helps with the backfiring, belching, and farting when decelerating, but there are additional things to consider.

Are the throttle bodies balanced and around 1 1/2 turns out from lightly bottomed? 

Has the seal at the header to silencer joint turned into fairy dust? 

Are you fully closing the throttle when engine braking? 

The hard starting and an uneven idle could be caused by a cracked Z-tube between crankcase and airbox.  A wonky engine temperature sensor can cause problems like you are experiencing as well.


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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
    

4Back to top Go down   Pops and backfire Empty Re: Pops and backfire on Sun Jan 05, 2020 4:08 pm

MartinW

MartinW
Life time member
Life time member
As per .75 & Dai plus throttle body leaks and incorrect injector spray patterns.
Regards Martin.


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K75s Hybrid
    

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