Jump to content

K75 refusing to start / timing check

fatty Sr

Recommended Posts

Hello out there,

I am new to the forum and struggling with a problem on a 1986 k75


What it is, I have put the K75 engine into a small car. I have wired everything up as should be and have got injectors (new) firing and I have also got spark. I have turned it over and get a few pops and bangs but nothing really to keep her going.


I disconnected the fuel pump and opened the throttle bodies full, turned her over and got fire in them so I am assuming that the timing could be be out OR i got the plug wires / coil wiring wrong.


I have been told and according to the haynes book that #1 cylinder is at the front (where forks should be)


#1 cylinder to first coil - black/blue wire to ICU

#2 cylinder to 2nd coil - black/ red wire to ICU

#3 cylinder to 3rd coil - black/green wire to ICU


any suggestions please let me know as I am fit to pull my hair out :eek:

Link to comment
Dennis Andress

The coils should be numbered. At the very least the wires to the primary side of the coils should be different. Look it up in a Clymer book.

Can you check fuel pressure? Is it the same as the stock fuel pumps?

The intake stubs between the head and throttle bodies have an o'ring to seal them against the head. The o'rings last about three years before the suck air.

Are you using the stock air box?

Open, clean and reassemble every electrical connection. A little bit of corrosion screws with things.

Does the engine run when it's installed on a bike?

Link to comment

Hello dennis,


Thanks for the reply. As I mentioned above i have the coils wired up according to the wiring diagram.


the fuel pump I have used is actually off a BMW car with a maximium pressure of 5 bar. The regulator on the K75 should release at 4.7 bar


I am using the stock airbox, plenum chamber and air filter. All electrical connections have been disconnected and cleaned prior to re-fitting in the car.


I can't put my finger on what could be causing this. could the engine be flooded??? Any ideas how to clear it if it is?

Link to comment
Dennis Andress

I've been told that worn injectors don't close completely. The resulting dribble could flood an engine. Pull them out leaving them attached to the fuel rail and turn on the fuel pump. Any drips?


I'm by no means an expert, but I'd troubleshoot by trying the stock fuel pump. Maybe the one you are using isn't maintaining pressure, maybe it's moving too much fuel and overwhelming the regulator.


I once got water into the ECU of an 85 K100. The cover is easy to remove and contact cleaner does a good job of removing contaminates.


The early K engines wouldn't run if there was a large air leak in the crankcase. Something as simple as leaving the oil filler plug off would mess with it.


Is the TPS adjusted? Throttles closed and adjust until you hear a soft click from the TPS. It should click again when the throttles are gently opened.


Ignition timing was done with a dial micrometer in the #1 hole, and a special tester that would indicate when the Hall effect sensor was in the "closed" place.

Link to comment

Dennis, Are you sat ready to answer my questions ?? :-) Thanks again. it's nice to bounce Ideas off someone else as when you been pulling your hair out, You can't see for the wood for the trees.


Well, I put a set of brand new (not reconditioned) injectors on the motor and have tested them and they shut off completely even with full line pressure.


I will take a look at water ingress into the ECU and see what turns up. Same goes for the air leak into the crankcase. I have just replaced the little breather pipe between the crankcase and the throttle body plenum chamber.


I will check the TPS as well as I can't remember hearing a click.


Link to comment


This topic is now archived and is closed to further replies.

  • Create New...