K100rt 1987 injectors not firing... HELP

[Bigbellytom]

Right I'm not one to just ask away so I have read up and tried a lot of stuff but I'm just about stumped now...

Bike... 1987 k100rt. Was running and riding perfect...

Been stripped to paint the frame and motor as it was looking a bit rough, I've done a fair bit of customisation to the cosmetics of the bike now and built it back up and it again ran fine....

I stripped the bike of all panels, plastics and tank, battery off and then set about cutting and welding the frame at the rear. My friend put the earth from the welder on the handle bars (doh)!! And it melted the earth from the throttle side to the main frame. Quickly noticed and then moved it to the frame. Replaced the earth wire.

Rebuilt the bike now and it won't start.... Firstly had noting... So diagnosed the starter had burnt out.... Replaced and the bike cranks... Now we have chased the issue round and found...

Spark is ok on all plugs.
Fuel pressure is good.
Fuel rail is good.
Injectors are not spraying fuel!!!

I have a spare donor bike so to eliminate parts we swapped all the following onto my bike and the same things happened... Bike cranks, spark is there, no fuel out injectors.

We put the below parts on the donor bike from mine and they all function fine...
Ecu
Ignition ecu (by headstock)
Fuel rail with injectors
Tank with pump

So we are literally stumped now!!! Everything from both bikes works on the donor bike but not mine. The welding and burning an earth could be a wild goose chase ... But has anyone any other ideas what it could be??? Really stumped??!!

[Bigbellytom]

One more big of info...

We have the injectors and rail sat on the block and crank the motor... On the donor bike they pulse and spit fuel out... On mine they don't. They give a tiny spray upon initial crank... Then no spray at all whilst cranking for how ever long u crank for... Then when u let off the ignition button u get a tiny sparky again... Like a tiny mist.

If you pull off te fuel pipes to the rail it fires fuel everywhere ??

[Laitch]

Check all the grounds on the bike—including the one that was replaced. Here's a thread concerning them. Read through the posts. There might be something in there for you.

[Martin]

Try using the fuel injection control unit of your donor bike.
Regards Martin.

[Bigbellytom]

Will go though all earths again and double check...

The fuel injection control unit has been swapped and checked... It's all functional.

[Martin]

Have you tried the fuel injection relay?
Regards Martin.

[Bigbellytom]

That I haven't tried..... Will try that this week and report back

[Inge K.]

As I have understand from earlier in this thread the fuel pump function OK, I asume this is when mounted
in the tank and doing starting attempts.
If so, the FI relay is OK as it also supplies the pump.
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and UK did go offline, good night.

[Nine80seven]

Synchronizing TBs stopped my handlebar click/knock whatever.  85K100RS.  FWIW they were way outta wack.  Also did the lean drop.  Don't know how this posted here as I was on the next thread?  I think.

[kennybobby]

1.  Are all the fuses okay?  Doesn't hurt to check them.

2.  There is a wire from pin 13 of the jetronic fuel control unit that connects to ground.  This wire is in the path that fires the injectors, and if it is fused open then injectors won't work.

[Bigbellytom]

Bit of an update...

Changed the Hall effect sensor... The bike starts...

BUT and its a big but....

It won't Rev over about 800 rpm. Yes 8 hundred. It's sounds lovely, ticks over at low revs but will not Rev at all. Once left running and it gets warm (not hot) it cuts out and won't start again????

Any ideas??

[Bigbellytom]

It won't make any difference as we had it running ages ago without them... But it has no clocks on it.

[Bigbellytom]

I'll update this in the hope it helps someone else in the future...

Read up online and the not revving thing pointed at the air mass flow sensor... Replaced that and the bike fired and runs straight away!!

So the hall sensor was shot and when trying to start it we had a massive backfire from easy start which blew the air box off... This knackered the sensor...

[kennybobby]

Thanks for the update--that will definitely help someone else down the road and you get some karma points...