gt550 dropping on to two

[boyoink]

Hi All,
My name is Wayne and I live in Lincoln. I have been a member and viewed this forum for about 10 years,mainly just viewing but I have made the odd comment.
Now the painful bit, my gt550 j model with kokosan ignition decided to fail on the left cylinder, I replaced a condenser and all was ok. Three hundred miles later
same thing happened again failed condenser l/h side. At this point I thought I would try the electronic ignition that I had previously purchased from T and GT parts
All then seemed fine for about 3-4 hundred miles then on to two cylinders the left one failing again. Replacement but not new coil on l/h side and away we go again
until yesterday about 3 hundred miles in summer an we are back to two cylinders l/h not working.
I have visually checked wiring and all looks good, I have stripped the carb and rebuilt it at least twice and I am sure it is good, the bikes charging system seems fine.
Any help gladly received. Thanks for viewing

[barney01]

Hi Wayne. Need a few questions answered first. What make is your elec ignition? Ie Boyer or Newtronic. Have you put a multimeter across the battery to see if its charging properly? Is the battery in good condition and fully charged.? Check to see you are getting as near to 12v at the coils ignition on as voltage can drop when the power goes around an old loom.
If you look under the tank follow the coil wires to where they plug into the loom. Give that connector plug a good clean with contact spray.
With regard to the carbs i know you say you are sure that they are clean but it is impossible to see into the internal passages and a good run through an ultrasonic cleaner is recommended. What is the inside of the petrol tank like? If there is any corrosion at all it will end up in the carb jets unless you fit an in-line filter.

[boyoink]

HI Barney,
Took on board what you said and went through all i could think of at the w/end and believe it or
not a plug cap seems to be the problem. Not had time to go too far but all now seems ok.
BUT watch this space, thanks so much for taking the time to reply.
Wayne

[Alan H]

Better sparks with non resistor plug caps, and if one of the old ones is dicky, the others might be two. (See what I did there?)

[barney01]

Great news Wayne. time to put some miles on!

[yeadon_m]

Hi Wayne,
I was reading about your intermittent fault and was thinking “Perhaps there’s a separate fault not in the bits you’ve fettled, wonder if it’s the HT lead or plug cap, or even the plug itself?”
I’ve had several NGK caps go bad, but to Alan’s point, they’ve been 5k ohm resistor caps. Also, more than once, with old coils still relying on their original HT leads, I’ve had poorly sparks. Sometimes trimming 5mm off the end of an old HT lead can fix poorly conduction.
I even had a spark plug go bad. Up to that point, I thought it was a myth & so-called failed NGK plugs were down to a dirty plug. But no, no matter how well I cleaned it, no spark!
I don’t know about others, but I’ve never had a truly bad coil, it’s always low or high tension connection.
Glad you appear to have found the fault.
Cheers!
Mike
Ps: risking slight controversy here, I’ve not noticed a systematic problem with resistor caps. One time I fitted resistor HT leads, resistor caps and resistor plugs to my GT380B, yet it was my easiest GT to start, ran well and idled beautifully. But then again, me & electrickery have never been beyond a nodding acquaintance.

[Alan H]

Good electrical connections between battery and coils can make a helluva difference when the 'lectric gets to the plugs Mike.
If you lose say, a volt at the low tension side of the coil due to resistance in the plugs and wiring, that would be nearly a 10% (rounded numbers) drop.
As the secondary (high tension) voltage could be as high as 50000 volts normally, a 10% drop would steal about 5000 volts from the plug.
That would mean a 10% less effective spark, and if the wiring connections are even worse, then the spark is even less effective.

[barney01]

Of course the best answer is to fit a relay and bypass the current loss around an old wiring loom. Simple. Cheap and very effective

[Alan H]

Ah, but that costs more than a bit o time & elbow grease!!

[boyoink]

Hi All.
Went out yesterday and all was fine for a while then back on two for a while then three. It seems to spend two thirds of the time
now on three but then drops back to two for a while. Left hand pot again. I have moved the wires over so now that coil h/t set up
etc are on the right side pot,I am hoping to get out on it at the w/end and will post what happens.
Thanks for all the input so far.