84 K100 Starting problem - K-Bikes.com - Excellence in Motion
 
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post #1 of 7 (permalink) Old Feb 15th, 2014, 5:28 pm Thread Starter
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84 K100 Starting problem

My K100 starts, bur runs only on 7-800 rpm for some secs before it stops. Dont take throttle - then it stops at once.
There are fuel and spark. But the spark on #2 is good, seems weeker at #1, #3 and #4(visual check). I've checked the sparks and wires- they are good. Checked them by connect them to #2 on the coil - and the spark was strong on all plugs.
Could the coils be defect?
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post #2 of 7 (permalink) Old Feb 16th, 2014, 3:02 pm
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Hi!

Have you checked the output terminals at the coils, ....and they don't look like the two green ones in the picture?
Also check that you got good (ground) connection at the ground terminal (in centre of coil).

To verify if the coils is the problem, you can test them of the bike (or just disconnected from the bikes wiring)........you just need a 12V power Source.

The terminal furthest away from the bike is the signal (-), the terminal in the center is (-) and the one closest to the bike is (+).
In the same moment you release the signal connector from the terminal, you should have a fat blue spark.
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post #3 of 7 (permalink) Old Feb 18th, 2014, 12:48 pm Thread Starter
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84 K100 Starting problem

Hi

Thanks for the advice.
I've measured the coil - and it seems ok - 9,5ohm on both coils.

But last night I found that the engine is not running properly on cylinder 4.
The exhaust is cold on this cylinder.
But spark is wet of petrol.

Think I need to check compression and if OK then check injector on cylinder 4.
Anything else I should check?

Thanks!
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post #4 of 7 (permalink) Old Feb 18th, 2014, 1:25 pm
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As plug #4 gets wet of fuel it points in the direction missing spark, rather than a injector problem.

Before doing more starting attempts you must dry the spark plug, preferably with a open flame.........or get a new spark plug.

If you got the OEM plug wires you must have adapters in the contact end of plugs and not only the 4mm threads,,,,,,
but some makes have this adapter built in as one piece.
Does the plug cap contacts look clean, if the spark plugs earlier have been used With only the 4mm threads and OEM wires...the contacts could be badly burnt.

The coil resistance is a bit off spec, should be...primary winding 2.6 ohms.....secondary 12,5 Kohms.

Last edited by IngeK; Feb 18th, 2014 at 1:34 pm.
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post #5 of 7 (permalink) Old Feb 18th, 2014, 4:18 pm
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Maybe just the spark plug wire. I had two bad ones measured with the Ohmeter. Those should be in the 5K range. And because they are carbon core wires you should twist/bend them as you measure, the carbon core may give a good reading in some positions but then show "open" as in 0 Ohms when the wire is bent or whatever.The ones on my bike showed good when bent in operating position, then bad when laid flat.

Same wires on the K1200RS and I know that they can cause problems, I also noticed one had been replaced on my bike before 32,000 kms when I bought it and two more I found defective at 60,000. All replaced with much cheaper copper core set.

Benelli 50cc at 14
Yamaha RD 200 at 16
Yamaha RD 350 at 17
Honda CB 750 F at 18
Honda V45 Sabre at 24
BMW K100RS at 27
BMW R100GS at 34
BMW K1200RS at 53
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post #6 of 7 (permalink) Old Feb 19th, 2014, 1:40 pm Thread Starter
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But there are spark at #4.
The engine also runs for 10-20-30 secs, but stops when turning on gas handle.
Dont help with choke.
And exhaust on #4 dont get warm during my start attempts.

I bought the bike on auction - and have not spoke with previous owner or know anything about the bikes history.
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post #7 of 7 (permalink) Old Feb 19th, 2014, 2:55 pm
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Fuel pressure ok? Fuel pressure regulator?? That one is vacuum operated, if the vacuum hose is leaking may bring on them symptoms.You'll have to remove the airbox to see that.

As for the plug wires vs spark....reread what I wrote up there. May be spark when you check with the plug out them maybe not when installed on the bike. Carbon wires...

Benelli 50cc at 14
Yamaha RD 200 at 16
Yamaha RD 350 at 17
Honda CB 750 F at 18
Honda V45 Sabre at 24
BMW K100RS at 27
BMW R100GS at 34
BMW K1200RS at 53
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