Hi all, my 1996 carby M900 went onto one cylinder at the weekend , ran fine for approx 20 miles then the vertical cylinder started with a misfire, then started cutting in and out, then backfires then nothing at all, I limped home on 1 cylinder, put it in the garage, dragged the Fireblade out and continued my ride, hopefully I’ll get time in the next week or so to have a look at the monster, I suspect it’s an electrical issue from the way it kept cutting in and out, has anyone else had the above symptoms?, cheers Mark.
It could be a number of things. I had similar symptoms when the r/r packed up on my M1100S, as the battery ran down there wasn’t enough juice to fire both coils & plugs and it limped along until eventually dying. Check the battery level whilst not running and check the volts across the battery terminals when it is running as that’s the r/r output, should be 13.5-14.5v Secindly, if not that start swapping over plugs and coils to see if the problem moves from one cylinder to the other. As it backfired, I agree that sounds like a no spark ie electrical issue rather than a fuel issue. The backfire is unburnt fuel/air in the exhaust from one cylinder being ignited by a hot, burnt fuel/air charge from the other cylinder.
Thanks Paul, I had a spare brand new coil and put that on with the same result, so that’s the coil pretty much ruled out, the charging system appears to be working, I’ve got a voltmeter fitted that reads bang on 14.2 volts when riding, I do think the battery is past its best but would have thought that because it’s charging whilst riding it should be ok? (I’m not positive on that though electrics are my weak point). I suppose I should consider the ignition pick up and Ignitor box for that cylinder as well, I’ll nick an Ignitor from my 900ss and try that, the awkward thing is it runs fine for about 20 miles before failing so it’s not a quick check, hmmm.
Are there separate crank position sensors on that model? I had my M900 so long ago now I can’t remember. Or are you referring to a CDI unit? . I’m gonna have to dig out my old manual for it.
If you have 14.2v on the voltmeter when riding then it’s probably not the r/r & battery. I’d also swap the plugs between the cylinders in case it a plug breaking down.
Yes it’s seperate pick ups and ignitors, 1 system per cylinder really, I recently fitted new plugs but it could be a faulty plug of course, I’ll swap them as you say, also I’ll check the resistance on the pickups, should be approx 95ohms I believe, if none of that points towards the issue I’ll really be scratching my head!
Hi thanks for the replies, I too suspected the coil because the issue happens after the bike has been running for 30 mins or so, luckily I had a brand new coil which I fitted but the problem remains, I’ll check the resistance on the pick up next, if that’s in limits I’ll take an igniter from my 900ss and try that, progress will be slow because I’m busy with work but I’ll report back, thanks for the help so far.
I dug out the wiring diagram and now see what you mean 28/29 are the plugs 26/27 are the coils 23 are the ignition modules 22 are the pick ups I guess it’s a case of swapping components, riding for 30 mins and repeating until you find the component that’s breaking down
Ha, that’s it pretty much Paul, (with the exception of being able to check the pick up & pick up loom with the multimeter), at least I’ve got the parts around me to swap which is a bonus . Trouble is time!, I’m test riding a new bike first thing tomorrow, then out for a ride, then lots of other stuff over the weekend, I doubt I’ll get more than an hour or so to look at the monster, it would be great if whatever is failing would just fail:-( Btw you didn’t say what number 18 is?
Well I still haven’t so much as looked at it, back in the UK tomorrow so hopefully I’ll get some time over the weekend.
