Misfire once warm (1150GS 1999)

[kenshabby]

Greetings from Tosser Ken. Got 'that' misfire which has manifested itself overnight and am still unsure wheather to investigate coils and/or Hall sender. I've found these three threads really useful and informative:


http://www.ukgser.com/forums/showthread.php?t=79386&highlight=misfire
http://www.ukgser.com/forums/showthread.php?t=120841&highlight=misfire
http://www.ukgser.com/forums/showthread.php?t=15917&highlight=misfire

...but I would really appreciate a bit more help. Symptoms are, on the face of it, classic coil breaking down but then I read about the Hall sender giving very similar symptoms and I'm now in doubt about what is causing the misfire.

Starts from cold fine and runs fine for about 8 - 9 miles, then misfires badly followed by the rev counter dropping to zero at which point there is no power at all. Occasionally it has a final burst of power once engine speed drops below @ 2000rpm (rev counter back up again at this point) but this is short lived and then the bike stops and refuses to start, or at best coughs and splutters, unless left for ten mins or so. Then after starting and running well for a few more miles its a repeat of the above.

My experience and work has taught me that this is classic coil breaking down, but then there is is this Hall sender business. I'm happy to replace the coils myself, but I fear its a trip to Bahnstormers for sender replacement.

I'm just wondering if there is a way of narrowing the cause down more precisely.

Last ride on the bike before all this was a couple of weekends ago, a round trip of 1000 miles to a rally in Scotland with no problems of course. And we had sun all weekend!

 

[Den]

Misfire accompanied with dodgy rev counter is usually hall sensor.
Coil would not affect rev counter.
I think?

 

[kenshabby]

Misfire accompanied with dodgy rev counter is usually hall sensor.
Coil would not affect rev counter.
I think?

Thanks Den. This is really what I'm unsure about actually. Being an electronic rev counter, I am assuming that it receives its' signals from one of the coils. Many years ago I fitted an aftermarket electronic rev counter to an old Bedford Van I was running, and a signal from the LT side of the coil was how it functioned.

 

[DrFarkoff]

Sounds more like the hall sensor the sensor is what tells the engine the crank position and when to fire the sparky things

If it were a coil pack or lead that shouldn't make the revcounter drop at all except by the amount of revs of the engine going off power certainly not to zero

By the way make sure and give your frame number when ordering I think the change in connection plug came in around there

I would however before you go spending £150 odd quid clean all the electric connectors and coat with ACF50 and check the sparkplug leads and plugs also the fuel tank connection, Check the wires at the ignition in case you have a wire that breaks and kills everything an overtight cable tie can do that too!

(Just to make sure there's nothing worse than having a spare bit that cost a fortune that you don't really need! )

Right Put down the cup of coffee and step back from the puter

Go Get it On

 

[Hong Kong Nick]

From my recent experiences ( ) I would just add that the Stick Coil (coil pack) problem starts as soon as you start the bike up - splutters straight from the push of the starter button, hardly seems to get up to any sensible revs and pulls away like a slow-moving train - plus the immediate backfiring and popping. 2 replaced coils later and all is fine
.

I should also add that my bike never actually stopped dead and I never encountered any sudden drops in power / revs - it just ran crap until the coil (left side was the problem but I replaced both) was replaced.

Good luck

Nick

 

[kenshabby]

Thanks Nick, I think that pretty much rules out coils then, based on your experience.

The bike has 50,000 showing, by the way, which may have some bearing on any expected faults at this mileage, but as it was one of the German Imports brought in by (as was) SPC, it might therefore have done more. In the 14,000 miles of my ownership, its been faultless until now, and a delightful ride. Just like the perfect woman!

 

[DrFarkoff]

From my recent experiences ( ) I would just add that the Stick Coil (coil pack) problem starts as soon as you start the bike up - splutters straight from the push of the starter button, hardly seems to get up to any sensible revs and pulls away like a slow-moving train - plus the immediate backfiring and popping. 2 replaced coils later and all is fine

Nick Stick coils are only on Twin spark engines late 2003 onwards

 

[Hong Kong Nick]

AHhhhhhh. I see. THX.

 

[kenshabby]

Solved.....and cured!

Well, firstly thanks for everyones valuable input all of which was helpful. Incredibly, the misfire was traced to a very terminally worn alternator belt. Replacement cured it ok, but just for good measure I had the bike put on diagnostics too, and everything checked out. A ride out this morning was faultless.

From this, would it be right to conclude that a constant and consistant charge from the alternator is quite critical for these engines? Something that the worn belt would have been incapable of providing.

All fixed, just in time for Winter......ho hum.

 

[davegs]

Misfire

Don't cheer too soon, the battery keeps the votage steady, this fault has just "cured it's self" but will probably return worn alrernator belt would be a mystery cause indeed. Start saving for new hall sensors.
dave ( I hate christmas ) Gs.

 

[kenshabby]

Thank you for decimating my renewed confidence in my machine.

 

[davegs]

Misfire

That is not the attitude to adopt. head in the sand does NOT work, I think you will possibly find that there was /is a fault on the cable from the hall sensors, possibly shorting to the engine case. When you changed the belt
you probably disturbed it and it got moved slightly and "cured" the fault. Most of us on here have considerable experience with these things and try to help, so, when the fault returns look at this cable.
Dave ( I hate christmas) GS. Roll on 2010!.

 

[Colban]

I'm also a bit dubious about the alternator belt as well.
Have you checked any of the wiring to the ignition switch?.
When the bikes running,try jiggling the wiring or turning the bars to the right.
May be a fractured wire causing the intermittent cutting out.