Hi all -
 
I ran into an interesting problem this week.  Had a dealer check and adjust the valves on my 1985 K100RS this Wednesday.  Picked up the bike around 7:30 pm and rode home with no problems.
 
Next morning she would not start – after sitting just 10 hours!  Cranks, can hear the fuel pump spin, and after sitting fuel is dripping from the exhaust header.  This morning I checked spark on each lead and there is a weak spark from each plug wire. 
 
This is the bike I spent most of November and December troubleshooting for a no start issue.  Finally found the throttle switch was bad and disconnected it (and it still is today).  Since then she’s been running great, no starting issues and actually throttle response does seem better.  There were no cold (or hot) start issues before I took her to the dealer for the valve check.
 
Could be coincidence, but seems like there is a connection here somewhere.  I’m going to install a new set of plug wires that I ordered last winter but never installed.  Also going to check the coil connections.  I did replace the coils with a used pair last winter when doing the troubleshooting, so I have a replacement set I’ll probably try as well.
 
I downloaded the troubleshooting guide from the Portal last winter and will dive into that if needed.  I can’t imagine that simply checking and adjusting valve clearance would cause the no start issue.  Could be the dealer’s mech bumped something with the coil wiring, but this seems remote as well.
 
One other thing.  I did re-fuel just before I dropped the bike off.  The gas station is about 1-2 miles from the dealer.  And, my house is about 3 miles from the dealer.  Will also check the gas to see if it might be bad, but I've use the same station in the past.  Could be bad gas?  They don't sell diesel, so I could not have pumped that by mistake.  The fuel filter was replaced last fall at the start of the initial no-start troubleshooting.

 
Thanks,

Tony Marts

Just to be clear, you have checked to see if they haven't readjusted the throttle switch? Otherwise it's bizarre, maybe take the plugs out and let them totally dry off..?

Fuel dripping on the exhaust header is not at all good. Sounds like a leak from a fuel line. But there are also two outlets under the tank for venting tank and for water drain off from that little hole you see on the left when you open the gas tank.

85RS is 8 valve engine and valve clearances are easy enough to do on them. No need to take camshafts out on them to either check or adjust them as far as I know.

If ever dropping a bike off to a dealer don't ever fill it up with juice. Its a pain for dealer getting a full tank of juice in case they have to drain it. Its particularly awkward with Ks because you end up with spillage. Guy I use over here will ask for tank to be near empty and he won't store petrol if one comes in full.

How well do you know the dealer and how well does he know his Ks? Do you know how much he removed to do the job? Worth checking in case something else got disturbed.

Snod Blatter wrote:Just to be clear, you have checked to see if they haven't readjusted the throttle switch? Otherwise it's bizarre, maybe take the plugs out and let them totally dry off..?

The connector is still disconnected (plug was left zip-tied to the frame where I had it).

It is puzzling.  Not looking forward to running through it again.

92KK 84WW Olaf wrote:Fuel dripping on the exhaust header is not at all good. Sounds like a leak from a fuel line. But there are also two outlets under the tank for venting tank and for water drain off from that little hole you see on the left when you open the gas tank.

85RS is 8 valve engine and valve clearances are easy enough to do on them. No need to take camshafts out on them to either check or adjust them as far as I know.

If ever dropping a bike off to a dealer don't ever fill it up with juice. Its a pain for dealer getting a full tank of juice in case they have to drain it. Its particularly awkward with Ks because you end up with spillage. Guy I use over here will ask for tank to be near empty and he won't store petrol if one comes in full.

How well do you know the dealer and how well does he know his Ks? Do you know how much he removed to do the job? Worth checking in case something else got disturbed.

New to this dealer, and I don't think they work on classic K's often.  I went there because it close to home.  Probably my undoing .

Worth checking the temp sensor. It needs to earth to the engine block thru the threaded body. If it's corroded it goes open circuit. The FICU will read infinite resistance and think it's REALLY cold and pump lots of fuel in.... so much that it flows out the exhaust valves and into the headers. We've seen this here at least once before.
To check.... Remove the plug to the FICU (under the seat) and measure the resistance between pin #10 and pin #13 (earth) counting pins and spaces from the lead end. At 20oC you should see around 2.5 kilohms.

My reasoning for asking about the dealer is that not all know the 8 valve doesn't need the camshafts out to adjust the clearances but does need a special tool and may have opened up a lot more which might include going under the tank with the possibility of disturbing some connections.

Finally got time to work on the bike. 

Replaced plug (high tension) wires with new set (leftover from last year, I took them off when I had starting problems last Aug.).

Also checked temp sensor reading at FICU plug.  Reads just under 3000 Ohms at 60-65 deg F.  

I'm going to double check the other readings at the FICU plug (airflow meter, etc.) before I try starting again.

If this doesn't cut it it's back to the troubleshooting guide.