So trying to cover the basics on my recent acquisition of a non running 85 K100.  The fuel pump kicks on when I press to start and fuel does splash thru the return line.

An induction timing light shows signal on the plug wires but I am getting wetted plugs.  I'm new to BMW but usually with a working fuel pump, wet plugs, and a spark signal I have a starting engine.  Timing, air, control module, haven't been verified yet so more diagnostics are in order.

Any tech links or ideas appreciated.  I am trying to navigate the site so as not to ask redundant questions.

Thanks 
Tim

Be sure you also pull the clutch lever or have a green neutral light on.

Are the plug leads in the correct order? Sounds like they might be incorrect.

As far as I recall the front coil is for cylinder 1 and 4, the rear is for 2 and 3. The coils are interchangeable and if someone bought a replacement it may have an incorrect sticker on it. Both terminals on a coil fire at the same time as it fires on both compression and exhaust strokes.

Early coils like on your K are notorious for failing so spark of itself may not be sufficient, it could be failing under compression.

Strangely enough, I am now not picking up any spark with the timing light. I saw a single flash and then nothing. You are correct on the cylinder/coil arrangement. I need to trace upstream.

Hello

Vic  bike had very similar signs  to what you have described 

We had spark as, checked by grounding out one plug at a time and crank the engine over 

We thought it may have been the temperature probe located at the bottom of the radiator stub  just in front of the throttle bodies  ( access from the right hand side ) 
We tested this in a jug of hot water and was found to be good   

We Ohm  meters across two pins on the big brain connection plug  ( Sorry cant remember which ones  and cant remember what reading we were meant to be get ) 
Someone will chime in hopefully 

This we found was down on the ohm reading  we ended up tracing the cables back along the loom and found the 4 wire factory joint  which sit on underneath the tank on the rear left hand side. we open this  joint and re did the ohm reading and it passed each way  ( strange ) 

Then we noticed that one off the male pins ( or it may have been a female pin )  had some how been pulled back inside the factory connector by just a few mils 
but just enough to break contact with the other side but look ok 

This was causing the over flooding of the engine in this case 

hope this helps

Much appreciated. I'm chasing no spark now. Definitely no shortage of possible failures. Thanks again!

Our problem was over fuelling wetting the plugs to much  to fire 

Work through CF flow chart on fault finding  K100 Tech section 

This will step you through each test where to measure and what to look for

To test the temp sensor you just need to meter across pins #10 and #13 (earth) on the ECU plug.
Correct reading should be 2.5kΩ @ 20ºc and around 300Ω @ operating temperature.

To count the pins hold the plug with cable out to the left and start counting from top/left counting the empty spaces as well.

The temp sensor earths through the sensor body to the engine. This can get corroded which will give a very high resistance reading to the ECU signalling a very cold engine. It will then grossly over fuel and the engine will flood.

Can you smell fuel from the tailpipe?

If the temp sensor checks out then look to the Ignition Control Unit (ICU) just behind the headstock. Sometimes the plug can come a little loose. It's only held on with a rubber cover. Also because of it's exposure to the weather there the pins can get a little corroded. Use contact cleaner (nothing abrasive) or just pull the plug and reseat it a few times to get it to make contact. If no luck, try the same with the ECU plug.

So after the used ICU came in I saw longer cycles of the starter spinning as well as the injectors clicking away.  Signals present at the coil connectors but I couldn't get a consistent signal on the plug wires.  I found that a set of 6 ohm plug wires from a 2001 beetle fit enough to keep moving forward.  With a plug pulled and grounded I couldn't get a spark but if I inserted a heavy gauge section of wire in place of the plug I could pull huge sparks.  I replaced the plugs.  
The bike immediately fired and ran for the first time in 6 months.  It burned off all of the smoke from being on the side stand.  I've only had it a week now.
It ran, warmed up, the idle started pulsing, it backfired a couple times and then died.  Attempts at warm restarts are spotty.  Cold attempts will usually get it running but once warming up it's tough to keep running.
The previous owner replaced the ECU with a used unit, the Hall sensor, temp sensor, the coils, and I continue to get great fuel pump action and clicking injectors, however on attempting warm restarts I am back short started cycles of a couple seconds.
I'm going to go through all of the usual suspect connectors and grounds with contact cleaner and dielectric grease and see if I can find the remaining gremlin.
Thanks for all of the great suggestions so far.  Progress has been made and the bike runs even if it's not for long.

Did h install the correct temp sensor? The 16v on looks the same but its not and causes all sorts of issues. Also make sure its not mounted on ptfe tape.

I'll try and sort that.  Thanks for the lead

It may be a faulty fuel pressure regulator. Had a similar problem on my K75 at one stage. Cheers Tom

Right on. Thanks!

Tom GR wrote:It may be a faulty fuel pressure regulator. Had a similar problem on my K75 at one stage. Cheers Tom

The vacuum pipe to the FPR if cracked also causes issues, check that first.

Thanks!  Hoping to get back on it tomorrow.