BMW K bikes (Bricks)


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1Back to top Go down   Throttle problem..... Empty Throttle problem..... Sun May 21, 2017 2:17 pm

eman-nyc

eman-nyc
active member
active member
Hello everyone,
Recently i have done some major work on my K100... the bike has been transformed into a Cafe Racer, had to switch a lot of parts.
managed to start the bike but as soon as the engine warms up the throttle starts to rev up on its own, can someone tell me if they had this issue before and how can it be solved....
Thank you

    

2Back to top Go down   Throttle problem..... Empty Re: Throttle problem..... Mon May 22, 2017 1:05 am

Holister

Holister
Life time member
Life time member
Sounds like an air/fuel mixture issue.
The FICU sets the fuel on the rich side on startup. As she warms the fuel is leaned till it reaches the correct mix at operating temp so the revs will pick up. You would normally use the 'idle throttle' (choke) to start but as she warms revs should settle at around 950rpm with the choke off. If you think its revving too much there are a few things you could check/adjust.

The Idle Throttle may need adjusting.
The throttle cable may need adjusting at the grip.
The throttle bodies (TB) may need balancing. This is the air bypass screw (BBS) on each TB.
TBs may not be closing at idle.
Your throttle position switch may be physically interfering with the TB shaft.
Air bypass screw on the MAF may need adjusting.

I think before you start you need to outline what engine modifications you've done, if any, so that advice is relevant.

Cheers


__________________________________________________

1989 K100RT     VIN  0097367 (naked)  
1996 K1100RS   VIN  0451808
 Throttle problem..... Austra12    Fuel:  95 Octane
Engine Oil: Nulon Full Synthetic 15W50
Gear Box Oil:  Nulon Synthetic 75W90
    

3Back to top Go down   Throttle problem..... Empty Re: Throttle problem..... Mon May 22, 2017 7:01 am

Dai

Dai
Life time member
Life time member
To add to Hollister's list...

If you've had the airbox and air intakes off and used Jubilee clips (worms drives) in place of the OEM clips, chances are that the worm drive on no.3 intake is fouling the throttle linkage bar.


__________________________________________________
1983 K100 naked upgraded to K100LT spec after spending time as an RS and an RT
1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

4Back to top Go down   Throttle problem..... Empty Re: Throttle problem..... Tue May 23, 2017 6:12 am

eman-nyc

eman-nyc
active member
active member
Thank you all, 
I havent done any modifications on engine, just replaced fuel injectors....can also fuel pump be the problem??

    

5Back to top Go down   Throttle problem..... Empty Re: Throttle problem..... Tue May 23, 2017 6:44 am

92KK 84WW Olaf

avatar
Life time member
Life time member
I had a similar problem on my LT.

Dai has mentioned it, my LT had Jubilee [worm drive] clips that were fouling the throttle linkage, throttle couldn't return to proper idle position.


__________________________________________________
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 0011157 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 58,200 miles. 
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 51,800 miles.
1983 K100RS 0004449 Odette R100 colours 58,000 miles. Sprint fairing now 63,390 miles

Past:
1968 Yamaha 80 YG1
1971 Yamaha 125 YAS-1
1968 Honda 125 SS
1970 Honda CD 175
1973 Honda CB500-4
Honda CX 500
    

6Back to top Go down   Throttle problem..... Empty Re: Throttle problem..... Tue May 23, 2017 7:07 am

Dai

Dai
Life time member
Life time member
If you have not done anything at all to the engine (and by that, I mean taken nothing off except the fuel injectors), then check the throttle cable routing. Is there any slack in the cable at the twistgrip? The twistgrip should move backwards and forwards by 2-3mm before it starts pulling the cable.


__________________________________________________
1983 K100 naked upgraded to K100LT spec after spending time as an RS and an RT
1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

7Back to top Go down   Throttle problem..... Empty Re: Throttle problem..... Tue May 23, 2017 8:21 am

duck

duck
Life time member
Life time member
I has this issue once. Cause: I'd inadvertently rotated the TPS so that it was holding the throttle open a bit. (I think it happened when I was putting the plenum back on after I'd replaced the TB boots.)


__________________________________________________
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
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
    

8Back to top Go down   Throttle problem..... Empty Re: Throttle problem..... Tue May 23, 2017 11:39 am

Holister

Holister
Life time member
Life time member
eman-nyc wrote:Thank you all, 
I havent done any modifications on engine, just replaced fuel injectors....can also fuel pump be the problem??
What fuel injectors did you install? There's a number on the side of the plastic part at the top which will look like this 0280150###

I doubt it will be the fuel pump.

What revs is it getting up to with no throttle?

The first thing to determine is if its revving because it's running a little lean OR the throttle is slightly engaged due to poor adjustment or something fouling it.
Take a look at all 4 spark plugs. Keep them in the order they came out and post a pic if you're not sure what you're looking at. If they are whitish/grey your engine is running lean.
What colour is your exhaust?

Take a look at the throttle stop on the TBs at the bottom of the cable. Is it coming to rest on the stop or short of the stop, leaving a gap? Also, as mentioned, the adjustment at the grip should be a tad loose.


__________________________________________________

1989 K100RT     VIN  0097367 (naked)  
1996 K1100RS   VIN  0451808
 Throttle problem..... Austra12    Fuel:  95 Octane
Engine Oil: Nulon Full Synthetic 15W50
Gear Box Oil:  Nulon Synthetic 75W90
    

9Back to top Go down   Throttle problem..... Empty Re: Throttle problem..... Tue May 23, 2017 11:55 am

eman-nyc

eman-nyc
active member
active member
Holister wrote:
eman-nyc wrote:Thank you all, 
I havent done any modifications on engine, just replaced fuel injectors....can also fuel pump be the problem??
What fuel injectors did you install? There's a number on the side of the plastic part at the top which will look like this 0280150###

I doubt it will be the fuel pump.

What revs is it getting up to with no throttle?

The first thing to determine is if its revving because it's running a little lean OR the throttle is slightly engaged due to poor adjustment or something fouling it.
Take a look at all 4 spark plugs. Keep them in the order they came out and post a pic if you're not sure what you're looking at. If they are whitish/grey your engine is running lean.
What colour is your exhaust?

Take a look at the throttle stop on the TBs at the bottom of the cable. Is it coming to rest on the stop or short of the stop, leaving a gap? Also, as mentioned, the adjustment at the grip should be a tad loose.
Spark plugs are brand new.....I am guessing it needs adjustment since the bike was completely disassembled then put back together.. however a friend/mechanic will be looking at it.... as soon as i get something i will keep ypu guys updated
thank you all for the feedback

    

10Back to top Go down   Throttle problem..... Empty Re: Throttle problem..... Fri Jun 02, 2017 3:31 pm

eman-nyc

eman-nyc
active member
active member
I did a vacum test and calibrated the throttle bodies..
 

but.. it seems that the intake manifolds are the problem....once the engine heats up it starts leaking air...... is there anything I can do before deciding to replace them (they are costly)....
maybe use gasket sealant...
or anybody has any other suggestions

Many thanks,
E

    

11Back to top Go down   Throttle problem..... Empty Re: Throttle problem..... Fri Jun 02, 2017 3:47 pm

Point-Seven-five

Point-Seven-five
Life time member
Life time member
I believe there is an o-ring at the base of the inlet manifold that may be hardened. 

Cheaper to replace than the manifold.


__________________________________________________
Present: 1991 K100RS "Moby Brick Too"
 
Past:
1994 K75RT "Ilsa, She Wolf of the SS"
1988 K100RS SE "Special Ed"
1994 K75S "Cheetos"
1992 K100RS "Moby Brick" R.I.P.
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

12Back to top Go down   Throttle problem..... Empty Re: Throttle problem..... Fri Jun 02, 2017 4:21 pm

duck

duck
Life time member
Life time member
You can test for air leaks while idling by:

1 - Spritz some water mist around the manifolds. If the RPMs go down then they're leaking.

2 - Spray some starter fluid or propane around the manifolds. If the RPMs go up then they're leaking.
(Use proper fire precautions if doing it this way.)

(I usually use starter the starter fluid method.)

If they are cracked or leaking then you should replace 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
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
    

13Back to top Go down   Throttle problem..... Empty Re: Throttle problem..... Fri Jun 02, 2017 4:32 pm

duck

duck
Life time member
Life time member
Point-Seven-five wrote:I believe there is an o-ring at the base of the inlet manifold that may be hardened. 

Cheaper to replace than the manifold.

The O-ring on 2V bike is built into the manifold and is not a separate part.

The 4V bikes have a separate O-ring there.


__________________________________________________
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
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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