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1Back to top Go down    Throttle problem..... on Sun May 21, 2017 10:47 pm

eman-nyc

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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    Re: Throttle problem..... on Mon May 22, 2017 9:35 am

Holister

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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


__________________________________________________
1988 K100RT VIN No. 0094680
1989 K100RT VIN No. 0097367 (naked)
1996 K1100RS VIN No. 0451808
Fuel: 95 Octane
Engine Oil:Nulon Full Synthetic 15W50
Gear Box Oil: Nulon Synthetic 75W90
    

3Back to top Go down    Re: Throttle problem..... on Mon May 22, 2017 3:31 pm

Dai

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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.


__________________________________________________
'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)
    

4Back to top Go down    Re: Throttle problem..... on Tue May 23, 2017 2:42 pm

eman-nyc

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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    Re: Throttle problem..... on Tue May 23, 2017 3:14 pm

92KK 84WW Olaf


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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 101,000 miles
1984 K100RT 0022575 Baja Red bought 36,000 now 83,150miles
    

6Back to top Go down    Re: Throttle problem..... on Tue May 23, 2017 3:37 pm

Dai

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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.


__________________________________________________
'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)
    

7Back to top Go down    Re: Throttle problem..... on Tue May 23, 2017 4:51 pm

duck

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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 (K75C fairing, K75 Belly pan, Ceramic chromed engine covers, 32/10 final drive)
K75 Frankenbrick (Paralever, K11 front end, hybrid ABS, K1100RS fairing, radial tires)
86 K75C Turbo w/ paralever
93 K1100RS
94 K1100RS
93 K1100LT
91 K1
93 K75S
http://www.ClassicKBikes.com
    

8Back to top Go down    Re: Throttle problem..... on Tue May 23, 2017 8:09 pm

Holister

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@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.


__________________________________________________
1988 K100RT VIN No. 0094680
1989 K100RT VIN No. 0097367 (naked)
1996 K1100RS VIN No. 0451808
Fuel: 95 Octane
Engine Oil:Nulon Full Synthetic 15W50
Gear Box Oil: Nulon Synthetic 75W90
    

9Back to top Go down    Re: Throttle problem..... on Tue May 23, 2017 8:25 pm

eman-nyc

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@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    Re: Throttle problem..... on Sat Jun 03, 2017 12:01 am

eman-nyc

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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    Re: Throttle problem..... on Sat Jun 03, 2017 12:17 am

Point-Seven-five

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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:
1994 K75RT
1994 K75S
1992 K100RS

Past:
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

12Back to top Go down    Re: Throttle problem..... on Sat Jun 03, 2017 12:51 am

duck

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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 (K75C fairing, K75 Belly pan, Ceramic chromed engine covers, 32/10 final drive)
K75 Frankenbrick (Paralever, K11 front end, hybrid ABS, K1100RS fairing, radial tires)
86 K75C Turbo w/ paralever
93 K1100RS
94 K1100RS
93 K1100LT
91 K1
93 K75S
http://www.ClassicKBikes.com
    

13Back to top Go down    Re: Throttle problem..... on Sat Jun 03, 2017 1:02 am

duck

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@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 (K75C fairing, K75 Belly pan, Ceramic chromed engine covers, 32/10 final drive)
K75 Frankenbrick (Paralever, K11 front end, hybrid ABS, K1100RS fairing, radial tires)
86 K75C Turbo w/ paralever
93 K1100RS
94 K1100RS
93 K1100LT
91 K1
93 K75S
http://www.ClassicKBikes.com
    

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