Checking Cold Starting Problem

Sidecarjohn · 8. August 2011

Read through numerous threads on problems with starting. Anyone have a systematic check list for working through such trouble with a 16 valve four, 1989 K1 vintage ?

Not starter motor, or battery issues, all fine. However, the one touch instant button start has disappeared. Symptoms point to fuel issues, but have an open mind about possibilities. New tank filter fitted, so no apparent blockages in that area. Also, consumption figures unchanged and acceptable.

Various settings of cold start lever employed initially, but settled on advice provided elsewhere of keeping starter button pressed and slowly manipulate cold start lever until motor struggles into life, throttle remaining untouched. In a few seconds motor chimes in fairly cleanly then all is well. Once up to temperature everything acceptable and no other trouble. What could it be and is there a sensible order to check ?

**eXBR** · 9. August 2011

My first guess indeed is a fuel problem. To be more precise, the temperature-sensor that regulates how much fuel is injected. If it is broken it tells the motronic of "arctic" temperatures. Hence, this regulates the air-fuel-mixture to very fat, leading to bad starting behaviour. By manipulating the cold-start-lever you do nothing else than throttling, opening the "flaps" (I don't know the correct english word). Hence you make the mixture more tolerable, enabling the engine to start. Once it is hot it's more tolerant anyways, and the sensor is not that much wrong anymore.
If you have the possibility, measuring CO² in the exhaust system with cold engine can hint on that. Maybe even the end of the exhaust system turns black from dust, smoke and such.

ReneZ · 12. August 2011

During starting the amount of fuel is determined with the signal of the air temperature sensor in the air mass meter in the older K's. No doubt your bike has an air temperature sensor as well, so have a look there. The Jetronic takes over when the bike revs over 750 rpm (IIRC), I would assume the Motronic has a similar set-up.
It could be due to older spark plugs or some humidity.

Sidecarjohn · 17. August 2011

Advice so far appreciated.
Have replaced spark plugs, but problem persists. About to take a trip, so will persevere with crude starting "remedy" and inspect sensors more thoroughly on return.

Ajays · 18. August 2011

eXBR,
The English call flaps..."Butterflies".
Just for future reference but flaps will do.
Cheers Ajays

**eXBR** · 18. August 2011

Thanks, Ajays!

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Checking Cold Starting Problem

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