BMW K bikes (Bricks)

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1Back to top Go down   Fuel pump breather tube Empty Fuel pump breather tube Sat Apr 19, 2014 12:35 pm


Gold member
Gold member
Have replaced the fuel pump on my K100 with one from a Peugeot 205/309 Gti as the original had been ' got at' by a previous owner. The new pump has an integral aluminium pre filter with no vent pipe connection. Surfing the Forum the indications are that it was fitted to eliminate pump cavitation caused, I assume, by air. What creates these air bubbles, is it under tank temperature, low fuel levels, vibration? Am I going to see this problem in normal day to day running. 
The pump change is my starting point at trying to eliminate poor cold starting and erratic tickover, it hasn't! so will look elsewhere. John


2Back to top Go down   Fuel pump breather tube Empty Re: Fuel pump breather tube Sat Apr 19, 2014 1:02 pm


Life time member
Life time member
For poor starting and erratic idle, cracks in the boots between the TBs and cylinder head would be my first suspect.

You can test for this by spaying some starter fluid around them at idle.  If the idle goes up then you have leaks and should replace all of them.

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

3Back to top Go down   Fuel pump breather tube Empty Re: Fuel pump breather tube Sat May 03, 2014 7:58 pm


Silver member
Silver member
after replacing my boots the bike starts instantly and has a very smoooth idle.
it was terrible  before with hard starting in cold weather and nothing i did would cure the poor idle.
well worth the effort.

85 k100rt current
04 vulcan 1500 classic sold
07 bonneville black sold
05 fjr1300 sold
04 r1150rt sold
91 k100lt sold
r80rt sold
85 K100 sold

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