Triumphrat

mistermellow001

My Bonnie started hitting on only one cylinder this morning. What's the first thing you do when one cylinder is firing and the other isn't? Check for spark. Guy's method: With engine running (poorly), pull one plug wire at a time. Left side killed the bike. Re-started. Right side made no difference. Progress! I plugged the wire back in and, with engine still running, ran my hand up toward the coil (under the tank) to check the connection.

ZAP!!!

Step next: Turn engine off.

The plug wire had come loose from the coil. I think I'll do a visual first next time.

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Guy

bonnevillebilly

Man! I hate learning the hard way.

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2001 Bonnie
1976 Bonnie

SHRuuM

Bet you don't do that again. Next time get a friend to touch it You had better luck than me a few years back, I dropped a lung on a long trip turned around came home and after faithfully getting me home on 200mi turnaround it turned out to be a lunched push rod. BUT SHE GOT ME HOME!

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Mods:Predators/fork stabilizer/AI removed/Keihin CR-S carbs/RaceTech fork springs/Nology wires&coil/Iridium plugs/Traxxion emulators/LSL sliders & damper/Napolean mirrors/Monza fuel cap/19t front sprkt/flyscreen/Pazzo Levers/Ohlins 36PL shocks

RedBird

Just for future info: On these 360 degree twins with one coil feeding both cylinders, it is better to connect a spare spark plug grounded to the engine, of course, to check for firing in a cylinder. If you just remove one spark plug wire and run the engine, there is a possibility of damaging the coil...of course in your case, you were already running the engine that way because of the loose spark plug wire at the coil.

Sounds like you checked out these electronic ignitions pretty good by feel...they do have a pretty good spark.

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Larry
2003 T-100 (790cc), NARK, NH Togas, 8100 rpm rev limiter, 158 main jets, 42 pilot jets (less than 1 turn out on pilot screws), stock needles--no shims. 13 A/F ratio from 1100 rpm to 4000 rpm; 12 A/F ratio from 4000 rpm to 6000 rpm; 13 A/F from 6000 rpm to 8100 rpm.:D
2007 Tiger 1050--White:D--SW-Motech crashbars, Skidmarx rear hugger/chain guard, Calsci +7 windscreen.

mistermellow001

The embarrassing thing is that in a past career I was a mechanic and should have known better. At least it was a quick way to get to an answer on the side of the road, with no diagnostic tools - like my spark tester for one.

On a serious note, I was disappointed to see how shallow the boot was at the coil-end of the plug wire - especially since the connection is downward-facing. Should a plug wire come loose, gravity is always at the ready to finish the job. I believe older Triumphs (and most bikes) have at least a horizontal secondary terminal. I wonder if rotating the coil 180 degrees (and therefore pointing the terminal upwards), with longer plug wires, would be better. I can't imagine this being a common problem, though.

Sheepdog

Now this was long ago, before there was as active an aftermarket as today, but I had a Suzuki T500 that I wanted to give a fatter spark to so I mounted a set of Delco coils with a new set of homemade plug wires. This enabled me to open up the spark plug gap a good bit and the bike started better and picked up a great deal of snap down low. However, on the inaugural ride one plug wires came loose. These big automotive coils had to be mounted on the downtubes so I could see the problem right away. Easy...all I have to do it reach down and....zap-WOW-fzzzt....and at 50 mph, no less. How I stayed upright is a mystery to me to this very day.

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2003 Bonneville T100 and 2007 Moto Guzzi California Vintage

BILLYSIM

Wow, you guys are really a hands-on bunch...

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Shoot safe, straight and often...

cdk80gs

On my old BSA A10 over 20 years ago I had it go down on one cylinder, what happened was the threads in the alloy head let go and the compression blew the spark plug out of the head, I wished the lead from the mag had come loose then but it didn't, the plug flew as far as it could until the HT lead reigned it in, it then pirouted around in a nice arc that brought the plug to rest in my lap and I ended up with several thousand volts through my bollocks, the bike had no kill switch and I was in too much pain and supprise to think too clearly, I just coasted to a halt and just about managed to get my feet down before collapsing, even the memory of it brings a tear to my eye.
Chris

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'04 Bonnie Black, Mototwin exhausts, Dynojet needles, 120 mains, K&N filter, AI & snorkle removed,18T

Baltobonneville

Cdk80gs, that's a good story!

Mrmellow, the good part of the story is that you diagnosed it quickly and easily, if a bit harshly!

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Marty
2005 Bonneville Blue 790cc, AI removed, Staintunes, Unifilter, no snorkel, 120/40/Thrux needle/1 shim/3 turns, fly screen, tacho, D9 gauge panel, center stand, Ikon 7610s, Hagon fork springs, gaiters, Pirelli Sport Demons, 3 seats.

BriGuy375

After having some wierd occurances going on, i tried quickly to pull a plug wire with the engine running to see if the engine was running only on 1 cylinder. I was having cold exhaust gas out of one side. The result was no matter which plug wire i pulled, the engine quit. I have read that this isnt the greatest thing to do, so i only did it once, but i read on here about people being able to pull aplug wire and have the engine stay running, but mine wont do that with either plug. Any ideas??

07 Bonneville, 865 cc AI removed bafflectomy-