Posted for another rider 
Vic the green cafe racer 


My bike is a 1985 K100 RS that I bought from a fellow in Maryborough.
It has done about 50,000 kilometres, started and ran nicely, and was a project bike for my daughter who was moving to her second bike with her open license.
I stripped everything off the bike and was left with the engine sitting on two besser blocks. The air box and throttle bodies were not removed.
All tappet clearances were good except for one exhaust shim clearance which was under spec. The water pump seal was replaced. Injectors cleaned and bench tested the backyard way. I had prob-lems with the first restart because I fitted the fuel lines the wrong way. I thought the pressure line went straight to the fuel pressure regulator. When I switched those around she started up and ran perfectly. I rode the bike around the back streets with no issues except for an intermittent short circuit in the right hand indicator circuit.
After swinging the tank 90 degrees to check wiring and sorting the indicators, I found the bike hard to start.

Symptoms:
Would start but there was no response when the throttle was opened and engine would eventually stop. Sub sequent attempts to start resulted in occasional backfires. Removed plugs and they were wet. I got a few short runs when I disconnected the tank and sprayed some Start U Bastard in the air box. I’m not sure if I have good spark because I might not have used the correct procedure to check the plugs.
I have a spare ECU, injector unit and hall sensor and will fit a new battery to the bike for the work-shop.

Fuelpump running? Check the connector.
Tempsensor under the radiator good? Check connector too, and all earthlines.

Sounds just like my screw-up recently. If the loom is still standard, on the left side of the bike just before the ECU there's a five-pin connector with four wires in it, probably buried under the main loom. If that's partly disconnected you'll get exactly what's described.

Other (and more likely) probablility is as Arlina says; the fuel pump connector on the left side of the tank isn't making contact(s) properly.

My immediate thought was the fuel pump connector A K will run and start when warm with the pump disconnected as the manifold vacuum is enough to draw just enough fuel through to let it run but stall as soon as the throttle is opened.

RicK G wrote:My immediate thought was the fuel pump connector A K will run and start when warm with the pump disconnected as the manifold vacuum is enough to draw just enough fuel through to let it run but stall as soon as the throttle is opened.

+1 

Upon twisting the tank 90 degrees the connectors on the right rear would disconnect themselves?

Thanks for the tips   

Martin , Myself hopefully a few other  ( open invitation )  will go over and see if we can get it to run  for Vic and his daughter

just a reminder  

Vic is holding a workshop this weekend  open   invite  

Jawohl, I will be attending

Regards

Dan

I intend to attend.

Will be interesting to go through the troubleshooting process.

See you there.

Mick

Matt I've got a yes from the slacko navy guy.
Regards Martin.

Thank you to every one who came along 

Its great to be able to say that the bike is now running and starting  with a press of the button 

Thanks charlie for the info on the phone

Had a great day today and a successful outcome. However currently my Brick is being held for ransom, so until I spring for springs I'm stuck using four wheels.  
Regards Martin.

Is that the snap ?

Yup it's supposed to be in one piece, there are two of them, one either side. The neighbor across the road works for Brisbane Garage Door's, so he is getting me a price on replacing both springs. He's a replacement for the mobile Hydraulic guy. Ya can't loose all the time.
Regards Martin.

G'Day,

A few pics from this mornings workshop.

What was it in the end?....Temp Sensor connector?

Sorry for leaving before job was done....but I am more scared of my wife than you lot.

Good to see camaraderie and fellowship and helping someone out and a lot of laughs while doing it.

Thanks for the Breakfast Vic.

Cheers Mick

All the cracks had gathered to the fray..





Surgical precision...

Mick if you hadn't left out of fear you'd now know what the problem was. Only those who stayed have had the benefit of enlightenment. We have now been sworn to secrecy, under the threat of disembowelment with a blunt soup spoon.
With regrets Martin.

Bugger I was about to tell him  as you were writing that

Matt let him ponder the error of his way's (fear of the wrath of wife). With suitable contrition and time all may be revealed.
Regards Martin.

Good pics Mick, hat’s off to the hardcore K’ers, was still drizzling & miserable when we packed up after the “success”, was nice & dry inside the ute  , I have no excuse 

Martin & Matt, you are evil....don’t leave poor Mick hangin’ , he’ll never sleep again 

Matt traced the main issue to a hidden harness plug under the tank related to the temp sensor circuit, the terminal had been pushed out of the back of the plug. That in conjunction with the other electrical gremlins found made for one grumpy K that was never going to run. After starting with no throttle fettling at all each cyl was allowed to kick back in (killing every mozzie in Vic’s street for the next decade) until the fast idle could be gently tweaked and all running on all 4.

Looks like after a few identified issues to sort by Vic in the future it looks like a really good bike, was a nice quiet runner without the usual K rattles etc.

Great effort by all who attended IMO. 

Regards

Dan

Ratz Dan, Mick needs to learn who is the more important his wife or us. 
Regards Martin.

well, there may be truth in that, if there’s a motionless blue K sitting forlornly 100KM out of Roma....

Regards

Dan

StandardK wrote:Matt traced the main issue to a hidden harness plug under the tank related to the temp sensor circuit, the terminal had been pushed out of the back of the plug.

Well bugger me! You mean I was right, but for the wrong reason - ! There's a first.

Dai wrote:Sounds just like my screw-up recently. If the loom is still standard, on the left side of the bike just before the ECU there's a five-pin connector with four wires in it, probably buried under the main loom. If that's partly disconnected you'll get exactly what's described.

Other (and more likely) probablility is as Arlina says; the fuel pump connector on the left side of the tank isn't making contact(s) properly.

Dai  you were spot on it was connector you stated 

The pin had move back just  far enough not to make contact with it mate in the other connector even when the connectors pushed together

Well done. Good troubleshooting. Vic will be stoked.

It was good to see a logical trouble shoot in action. When I left you knew you had no continuity to temp sensor, good work in finding the break.

Learned a  lot and no longer scared of temp sensors....still extremely scared of wife

On the Brick again, I had to attend the workshop on four wheels as my garage door spring snapped as I was about to leave. Luckily my new neighbor does garage door installations, 15 minutes this arvo and I'm back on the road again Yeeeee Haaaa.
Regards Martin.

Hey guys, well done. I better ask where this mysterious faulty connector is. I have some running problems  too. 
I should start a new thread about this, but will first do a search of the forum. I expect the answer I  seek us out there somewhere!

The connector with the faulty pin connection is under the tank on the left hand side. It's a five pin connector it is located on the Haynes wiring diagram 70mm down from the top of the page and 75 mm in from the righthand edge of the page with the following colours and markings starting from the top U purple 15 green red tracer going to purple 86 black yellow tracer T pink green tracer TD yellow.
Regards Martin.

Thank you Martin. Tomorrow I will embark on a search to find my fault!

Michael start a new post and describe the fault.
Regards Martin.