Twelve months ago I purchased a '90 K100RS 16V with 175,000km on clock that was screaming out for a restoration.  Although the bike was in poor condition cosmetically, the engine was in great condition, very quiet, smooth and very easy to start hot or cold. The restoration is now finished and the bike looks fantastic but during the restoration the engine wasn't started for about 3 or 4 months and when i tried to start it it was flooding with too much fuel.  I could get the engine to start by giving it lots of throttle while cranking the engine over and when it started it was not running on all cylinders and had lots of light coloured smoke (not blue) coming out of the exhaust and stunk of fuel.

I checked the plug leads.
Changed the spark plugs.
Replaced one coil that appeared to be a bit sus.
Cleaned all connections on bike (including ECU) with contact cleaner.
Dosed the near empty fuel tank with a full bottle of Injector Clean.
Tried starting with the Throttle Position Switch disconnected (no difference).

Managed to get the bike started and held it on 2000rpm until the smoke cleared and started to run smooth which took about 8 mins.  When the revs were dropped it started to flood again.  The next day it started a lot easier so I took it for a ride and it quite well until I restarted the bike after a 15 minute spell. It flooded again although nowhere as bad as previously and cleared very quickly, so it appeared the Injector Clean treatment was working.  I refilled the tank on the way home.  Later that day when the engine cooled down I tried to start the engine and it started perfectly.  I rode the bike to work for the next four days without any problems, then it all started again.

I fitted the injectors out of my K1100RS.
Fitted new Fuel Pressure Regulator (FPR).
Replaced a dodgy vacuum hose going to the FPR.

On first attempt to start engine with no throttle, the engine would start and idle at very low revs (about 400rpm) and any attempt to increase revs resulted in the engine stopping, then it was back to needing lots of throttle when trying to start the engine followed by lots of smoke and smell of fuel again.  I removed the plugs and they were very wet with fuel.

I'm running out of ideas and thinking that the ECU may be faulty.  If anyone has some suggestions I would be extremely grateful.

Did you check the crankcase ventilation hose for integrity, leaks and blockage from its attachment point at the crankcase to its connection inside the airbox?

Laitch wrote:Did you check the crankcase ventilation hose for integrity, leaks and blockage from its attachment point at the crankcase to its connection inside the airbox?

Thanks Laitch, No I haven't checked all the hoses to and from the the air cleaner box.  The one you refer to that goes to the crankcase has cracked up due to age but the previous owner plastered some silicone sealer around the cracked up area.  I intend to replace all these hoses and check out the separator in the air cleaner box.  I didn't think that these would have contributed to my problems as it ran fine for almost a week.  It is however on my list as the next job to do.

A bad or disconnected coolant temp sensor (the one at the top front of the head) can cause overfueling or flooding.

I think klompy had exactly the same issue when trying to leave coffs harbour  one time, on a group meet

removal of the fuses and reinserting them fixed the issue at that time , ran like a dream after . (but that was a k100 8 valve ) but worth a try .

GB777 wrote:

Laitch wrote:Did you check the crankcase ventilation hose for integrity, leaks and blockage from its attachment point at the crankcase to its connection inside the airbox?

Thanks Laitch, No I haven't checked all the hoses to and from the the air cleaner box.  The one you refer to that goes to the crankcase has cracked up due to age but the previous owner plastered some silicone sealer around the cracked up area.  I intend to replace all these hoses and check out the separator in the air cleaner box.  I didn't think that these would have contributed to my problems as it ran fine for almost a week.  It is however on my list as the next job to do.

I have now replaced one hose that was leaking due to age related cracks. No improvement with engine flooding on startup.

charlie99 wrote:I think klompy had exactly the same issue when trying to leave coffs harbour  one time, on a group meet

removal of the fuses and reinserting them fixed the issue at that time , ran like a dream after . (but that was a k100 8 valve ) but worth a try .

Tried removing and re-inserting fuses with no change to flooding.

duck wrote:A bad or disconnected coolant temp sensor (the one at the top front of the head) can cause overfueling or flooding.

Replaced the Temp Sensor, re-applied Heat Sink Compound to Ignition Amplifier with no change to flooding issues. Is there only the two locations for all the earth wires, which is below the coils and another behind the starter motor?  The K100 16V doesn't seem to have the earth connections to the frame under the tank like on the K1100.
What is the purpose of the Motronics relay?

You better look again.  The 16 valve K100 has a ground connection point on the left hand side just under the frame tube about 9" back from the steering head.  It's the same as earlier K bikes.  Make sure everything there is nice and clean and shiny.

I'm not sure how to check it, but your throttle position sensor or it's wiring may be whack and telling the Motronic that the throttle is open.  Having the throttle open when starting, even a little bit, will flood the engine.  No need to get into how I know this.

When the engine floods, unplug the tank connector and crank the engine for 10-15 seconds.  That will blow the excess fuel out and you might get a couple of burps out of the engine to confirm that it is clear.  Then plug it back in and try to start again with no choke or throttle.  The engine should try to start.

GB777,
Check the voltage of the throttle position sensor (lot of info on the net),this sounds like it is out of adjustment or gone bad. I believe that when there is no signal from the TPS the motronic goes into a default fuel map that is very rich but do not know for a fact.
Good luck and keep us posted.