BMW K bikes (Bricks)

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1Back to top Go down    Air screw balancing on Sat May 19, 2018 8:58 am

nobbylon

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A question to those that know please.†
Trying to balance my K100 with carbtune and numbers 1,2 and 4 cylinders are requiring 1.24-1.5 turns out but the closest I can get no.3 is when the screw is 2.5 turns out and turning out beyond this has no further effect. Does this mean that I possibly have an air leak between throttle body and intake stub on no.3?†
Bike new to me so canít say if the body sync screws have been altered. There certainly isnít any paint on them. Bike runs fine, no popping etc, idles at 1000-1100. Should I just leave it as is?
thanks j


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K100RS July 1989
K100 Dec 1983†
R90s June 1975
R75/6 Feb 1976
F650GD May 2001
    

2Back to top Go down    Re: Air screw balancing on Sat May 19, 2018 9:41 am

Dai

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Yup - sounds just like what happened to me and I had an air leak in the inlet rubber (the one on top). I replaced the lot - inlet rubbers and inlet manifolds (the ones on the bottom). IIRC it cost me £60 or thereabouts from Motorworks. After I'd changed mine the idle dropped from1100rpm to 800rpm with no other changes, so I then wound it back up to the recommended 960rpm -ish.


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'83 K100 upgraded to K100RS spec
Others...
'78 Moto Guzzi 850-T3, '79 Moto Guzzi 850-T3 California,'93 Moto Guzzi 1100ie California,
'03 Suzuki Blandit GSF600SK3 (NFS any more because wifey has claimed it)
    

3Back to top Go down    Re: Air screw balancing on Sat May 19, 2018 10:20 am

nobbylon

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Would the top rubbers have any effect? The rubbers between the throttle bodies and block sure. Ridiculously expensive for a piece of rubber. £34 for these and a fiver for the top ones.


__________________________________________________
K100RS July 1989
K100 Dec 1983†
R90s June 1975
R75/6 Feb 1976
F650GD May 2001
    

4Back to top Go down    Re: Air screw balancing on Sat May 19, 2018 10:50 am

duck

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It's probably the bottom ones.† You can confirm by spraying some starter fluid or other flammable substance around them.† If the idle increases then that tells you that there's a leak.† Or you can spray some water mist around them and see if the idle decreases.


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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
http://www.ClassicKBikes.com
    

5Back to top Go down    Synchronization throttle bodies on Sat May 19, 2018 11:24 am

caveman

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Did you check valve clearance first?

    

6Back to top Go down    Re: Air screw balancing on Sat May 19, 2018 12:23 pm

nobbylon

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valve clearances, new timing chain and guides done a couple of weeks back. The bike runs superbly but I like to mess. Iím suspecting the weird buzzy sound or nigh frequency rattle from 2500-3000 rpm is either the alternator drive bearing inside the rear casing or more likely a couple of worn rivets on the output shaft with a worn backlash circlip.
Will keep riding and see what happens.†
Iím busy replacing the fork stanchions on my 75/6 so it will have to wait!


__________________________________________________
K100RS July 1989
K100 Dec 1983†
R90s June 1975
R75/6 Feb 1976
F650GD May 2001
    

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