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1Back to top Go down   Bad throttle pick-up from idle. Empty Bad throttle pick-up from idle. Sun Apr 26, 2015 12:04 pm


active member
active member
Hi All,
1985 K100RS
Bike starts ok hot or cold but idle very lumpy when cold.
Opening throttle from cold, engine stutters and usually stops about 1200 rpm, coaxing temp up, can drive bike when warm. Acceleration is good but VERY slight misfire can be felt occasionally on steady cruise condition.
Have done the following.
Replaced Hall Effect Triggers         Replaced injector relay
Replaced fuel pump                     Replaced fuel pressure regulator (twice)
Replaced fuel filter                      Replaced crankcase vent hose
Replaced water temp sensor         Replaced filters & pintle caps on injectors
Checked injectors on 9 volt           Checked fuel pressure - approx  35psi at rail - pump blows off about 70psi
Connected HT strobe & LED on injectors & run engine to try and see if either misses some pulses - all look ok.
One final "pointer"
If when throttling up expecting engine to cut, I momentarily pinch the fuel hose leading to fuel regulator the engine picks up perfectly??? 
I believe ignition is ok
Could it be EFI sending wrong pulse duration to injectors??
I am at wits end - any suggestions gratefully accepted.


2Back to top Go down   Bad throttle pick-up from idle. Empty Re: Bad throttle pick-up from idle. Sun Apr 26, 2015 11:23 pm


Silver member
Silver member
What about spark plugs and wires?  I had similar symptoms and it turned out to be a plug wire not fully cliced on to a plug.  Missed a bit off idle but once the plug was hot it ran fine.


Dave Evans
'Kafe Racer'

1990 K75RT
1985 K100 Kafe Racer

3Back to top Go down   Bad throttle pick-up from idle. Empty Re: Bad throttle pick-up from idle. Mon Apr 27, 2015 4:06 am

92KK 84WW Olaf

Life time member
Life time member
I had a similar problem with the LT some time back. Wasn't long after a service. One of the new plugs was the problem. Which also makes me wonder
what plugs and leads are you running? If the leads are originals then non resistor plugs. Just making sure yours is 8 valve engine.

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 48,061 miles.
1983 K100RS 0004449 Odette R100 colours 58,000 miles. Sprint fairing now 61,190 miles

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

4Back to top Go down   Bad throttle pick-up from idle. Empty Taking advice: Tue Apr 28, 2015 6:42 pm


active member
active member
K.R. /Olaf

Two good points -  Plugs are nd always have been NGK 7AE, ie non resistors.

If the weather is o.k. tomorrow, ( bike lives outdoors and I'm an arthritic wimp ),  I'll put the old ones back in as I know they were good anyway - only changed them as a matter of habit, and ensure caps are properly located. 
Will advise outcome. 

Plugs, caps & coils o.k.
Checked air flow meter & temp sensor per Crazy Frog's check list - o.k.
Fitted a different (used) EFI unit. Slightly better.
Tweeked CO adjustment 1/2 turn ACW  - no means of measuring but idle sweeter. Went for a 20 mile run & everything seemed perfect. Reduced idle speed on return. Have not had opportunity to try a cold start again.
If everything fine will try the old EFI again - just for curiosity.

Last edited by WINGLESS on Sun May 03, 2015 5:51 pm; edited 2 times in total (Reason for editing : Additional information)


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