Cil #3 dont burn mixture

[Eliseo Monteverde]

Hello;

Cil #3 has a nice blue and flat spark, but when I tight the spark plug on his place,only fires when the cap is separeted about 3/8 (10mm) from the spark plug.
What could be the problem?

Thanks in advance.

Eliseo.

[Anonymous]

try a new sparkplug or if you dont want to do that, trade over two of your plugs and see if the problem follows the plug or stays put on #3.

[Eliseo Monteverde]

I?ve tried that ,with new and old plugs, and always is in the same cilinder. :?

[Anonymous]

O.K., now trade over the two coils complete with their plug wires and see what happens. I wonder if the cap is "tracking". If possible trade #2 and #3 wires before changing coils. 2 and 3 both spark at the same time believe it or not.

[Eliseo Monteverde]

Well, cap #3 is in place of cap #2, and viceversa..but the problem continues.
I forgot to tell , that when I replace the plug #3 runs fine for some kilometers, it dosn?t mind if the plug is old or new, but sooner or later it needs to be replaced again.
#3 spark plug is comanded by #1 coil, isn?t it?
If it were a #1 coil, the #1 spark plug also would have problems, but at this case not.
It could be a wire problem?

Thanks for your time.

[KEITH KRAUSE]

After the plug stops firing, what does it look like?
Is it dark or black colored? Is there fuel on it?

[Anonymous]

Well, cap #3 is in place of cap #2, and viceversa..but the problem continues.
I forgot to tell , that when I replace the plug #3 runs fine for some kilometers, it dosn?t mind if the plug is old or new, but sooner or later it needs to be replaced again.
#3 spark plug is comanded by #1 coil, isn?t it?
If it were a #1 coil, the #1 spark plug also would have problems, but at this case not.
It could be a wire problem?

Thanks for your time.

1 and 4 fire together along with 2 and 3.

[Eliseo Monteverde]

After the plug stops firing, what does it look like?
Is it dark or black colored? Is there fuel on it?

It is dark with fuel on it.

...and if I try this plug after stops firing in other cilinder , this plug fires with a little orange spark, so it seems that it has been killed by cylinder #3.

[wayne cooper]

bad spark

first of all do you have a service manual? If you do-check resistance values for your igition with a multi meter set to resistence(ohms).Pulling the cap away in order to help a plug fire better is an old trick so i am assuming you have been around engines for some time.this is a shot in the dark but check both primary and secondary coil windings as well as the caps themselves,a compression check might be a good idea while you are at it.If this checks out ok I would look into your fuel delivery system-check for stuck floats or air leaks The latter can be checked with a spray lubricant such as WD-40 or any other brand of penetrating oil by spraying the manifold rubbers as the oil will temporarilly seal small air leaks.

[KEITH KRAUSE]

OK. You've tried putting #2 plug cap on #3 and there was no difference.
You also have a good blue spark, but after a short ride the plug fouls and you see a weak orange spark. If you then replace the fouled plug with a new one, the good blue spark returns and the cylinder runs good for a short time. There's fuel on the plug. The other cylinders run good. Correct???
It must be mixture related, either too much fuel or too little air in the mixture. Of course, it could also be poor compression.
This is #3 carb, as you sit on the bike, correct? I just want to be sure that it's not the carb that supplies vacuum to the petcock.
If the compression is good, it's the carb.
Possible causes: dirty or plugged carb passages...loose jet...float level too rich...float sticking...float valve worn or not seating (any fuel leaking at the carb or airbox drain?)... worn or missing float valve seat gasket/o-ring...choke plunger not sealing...poor carb vacuum synch (too much vacuum as compared to the others)...mixture screw set too rich.
Any other symptoms? Leaking fuel anywhere, smell unburned fuel, dark/black exhaust?

[Eliseo Monteverde]

Re: bad spark

first of all do you have a service manual?

Yes I have.

I have checked air leaks in the manifolds rubbers with WD-40 but it seems not to be an air leak;manifolds rubbers are in very good shape (thanks God).

OK. You've tried putting #2 plug cap on #3 and there was no difference.
You also have a good blue spark, but after a short ride the plug fouls and you see a weak orange spark. If you then replace the fouled plug with a new one, the good blue spark returns and the cylinder runs good for a short time. There's fuel on the plug. The other cylinders run good. Correct???

Yes it is.
I must add, that the replaced fouled plug does not have any more a blue spark even trying in other cylinder.
Beleave or not,at this moment I am riding carring with 20 old plugs in my bag. :roll:

Mixture screws are setting 1 3/4 turns out.

This is #3 carb, as you sit on the bike, correct?

Yes it is.

In the beggining this started after 2 weeks without ridding, so I tougth it was a clogged or dirty jet , then I decided to clean the carbs out (specially air passages).
I did not find a loosened jet.
Float level was at 22 mm from the gasket surface, now it is at 24 mm.
Float valve seat is like new, only a bit shine.
There is not an external fuel leak.
It is possible smell unburned fuel only when the plug dies.
When I cleaned the carbs, I did a manual synch taking as a reference carb #3 and testing with a piece of papper between the carb body and the butterfly valve.

Next steps will be ,

Wet and dry test compression.
Check ignition resistance values.
Check vacuum synch with the mercury synch tool.
Check float level at idle speed.
....And how check the choke plunger if is not sealing?
Mostly times I have this fouled plug problem when I start the engine with choke, others at 1/4 or 1/2 constant throtle.

Thanks for your time and your interest in help me.

Eliseo

[Eliseo Monteverde]

1 and 4 fire together along with 2 and 3.

Thanks Swanny,

You are rigth.

For a moment I was confused.

[Anonymous]

The fact that the spark ever goes orange makes me suspect the coil. It may be failing. Not failed. Trade coils and see if the problem follows the coil or stays put. That would tell you for sure if it is the coil.

[Anonymous]

The fact that the spark ever goes orange makes me suspect the coil. It may be failing. Not failed. Trade coils and see if the problem follows the coil or stays put. That would tell you for sure if it is the coil.

I'd vote for the coil right now. It may be possible that the coil output deteriorates for both cylinders, but #2 is carburated spot on and will tolerate the reduced spark and #3 won't. Trade the coils as 3phase suggests. He has a pedigree electrical name.

[Eliseo Monteverde]

[quote="Swanny"]

Trade the coils as 3phase suggests. He has a pedigree electrical name.

Ok.