Sorry to post another thread on this subject, but I did not want to detract from the specific questions other owners have asked.

Yesterday I was riding from Canberra ACT to Bowral NSW (in Australia). I filled up in Canberra, and about 140km into the ride, the engine started to bog down. I had to increase the throttle position to maintain speed. The engine also felt like it was intermittently stopping/starting. I am not sure if this is a vital piece of the puzzle or not, but it was also about this time that it started to drizzle/very light rain. There was the odd couple of drops of water falling behind the fairing (K100RS 1989), but certainly nothing looked like it was getting drenched. I was wearing a summer jacket and kevlar jeans and did not get wet.

I was concerned that the engine would stop when I stopped the bike, however, when I stopped, the engine would idle normally. The engine would start to complain and bog down when the RPM increased. When it was running, it felt slightly rougher than normal, but not real bad. I managed to limp home the last 30km or so.

I was tired when I got home, so did not check straight away, but an hour or so later when I went back to the garage, I pulled off the coil cover and everything looked dry. I did spray a little WD40 around the coil connections and the throttle position sensor plug (but did not take anything apart).

Today (dry and almost sunny) - it rides fine.

From my reading, the issue could be caused by a number of problems:

Leaking air boots etc.

Fuel issues - contaminated filter etc.

Electrical problems.

My gut feeling is it is electrical, but asking for advice. This is a K100RS 1989. It is new to me with 134,000km on the clock. I bought the bike because I had one briefly in the 90's and miss it! However, I am not very familiar with the BMW or K systems. I have just finished a nut and bolt restoration of a 1982 Honda CB900F, so I am reasonably comfortable having a go at things myself.  I suspect it will be wise to completely replace all rubber airboats hoses etc. Is there a link to a comprehensive parts list for this? I am not asking because I am lazy, it is just that if you forget something, freight costs a fortune for things to come to Australia. Next issue is electrics. I have heard that it is good practice to pull apart all connectors, clean and reassemble with dielectric grease. I know this is going to sound dumb, but I have not seen the type of connectors on the BMW before with the wire retainer. How do you undo this? I don't want to break a connector.

Lastly, any clues as to what the likely diagnosis is?

Thanks for your help,

Chris

I am presuming this is a 16v RS and if so they arent as prone to air leaks as the earlier 8v models due to not having the MAF (air flow sensor), they take a reading from the throttle position sensor at the throttle bodies. Only leaks under the throttle bodies will affect the running.
I would be looking for electrical problems. Was the road wet enough to throw up a spray?
Check the coils and while running spray some water from a spray bottle so it mists over the coils and even check in the dark for sparks around the coils.

Thanks for taking the time to respond Rick.

I should have been a little more precise with my bike description. It is a 1989 K100RS 8 valve with the ABS removed.

The road was slick, but no pooling water, so some minor road spray may have occurred, but not sheets of water. I will try your spray bottle tip tonight when it is dark.

Any tips on disassembling the connectors with the wire retaining clip (such as at the throttle position sensor)?

Thanks again,

Chris

To get the clips out use a fine tip screwdriver or a scribe and get under the clip on the short side of the plug and the wire will lift away, then move the end till it is about half way along that side and both sides will be released and the plug can come off. Put the wire back in place then push it back on. Once it is off then you can see how it is fitted then it's easy.

Thanks Rick.

Any progress?

Regarding the wire clips...

I used to remove them as Rick suggested above...

But now I just pull the plugs directly off. I dont think you need to remove the wire clip, it just provides extra grip to hold the plug onto what ever its connected to and stop it coming loose.

Could be wrong of course, but it works for me and I havnt damaged or broken any in the process. 

And I mean, it does seem like an awfully fiddly way to design connectors if you need to poke around with a tiny screw driver to remove a tiny wire clip from connectors that are often in hard to reach places (such as the water temp stub)...

just my 2c...