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Cil #3 dont burn mixture

  • Thread starter Thread starter Eliseo Monteverde
  • Start date Start date
E

Eliseo Monteverde

Guest
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.
 
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.
 
I?ve tried that ,with new and old plugs, and always is in the same cilinder. :?
 
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.
 
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.
 
After the plug stops firing, what does it look like?
Is it dark or black colored? Is there fuel on it?
 
Eliseo Monteverde said:
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.
Click to expand...
1 and 4 fire together along with 2 and 3.
 
KEITH KRAUSE said:
After the plug stops firing, what does it look like?
Is it dark or black colored? Is there fuel on it?
Click to expand...

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.
 
bad spark

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.
 
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?
 
Re: bad spark

Re: bad spark

wayne cooper said:
first of all do you have a service manual?
Click to expand...

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).

KEITH KRAUSE said:
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???
Click to expand...

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.

KEITH KRAUSE said:
This is #3 carb, as you sit on the bike, correct?
Click to expand...

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
 
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.
 
3phase said:
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.
Click to expand...
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. :wink:
 
Re: possible coil problem... why would installing a new plug into the cap make the fat blue spark return as he says? A fouled plug can obviously deter good spark, but if the coil really is weak, then installing a new plug would still show a weak read, and #2 should also have a weak spark and similar problems.
 
After your compression check and carb synch, etc, (if the compression is good) let us know what happens.
To test the choke plungers for sealing, you would have to blow into the passage that leads to the choke starter jet/tube. With the plungers down, no air should be heard to escape. Your fouling at 1/4 and 1/2 throttle positions wouldn't be choke related. The choke is bypassed as soon as the thottle is opened that far. There can be a minimal mixture change, but not enough to cause your problem.
You foul the plug at warm up with the choke because the mixture is already too rich in that cylinder. Either from a carb mixture problem, weak spark, or poor compression.
Is 24mm the factory setting for the floats. Also, the measurement should be done with the bowl gasket removed.
 
KEITH KRAUSE said:
Re: possible coil problem... why would installing a new plug into the cap make the fat blue spark return as he says? A fouled plug can obviously deter good spark, but if the coil really is weak, then installing a new plug would still show a weak read, and #2 should also have a weak spark and similar problems.
Click to expand...
I know Keith, and I agree. But right now switching coils is the easiest thing to do, and when I troubleshoot I try to take care of the easy possiblities first (like making sure the TV is plugged in before taking the back off.) :wink:

The carburators would be the only other possibility (if compression is good). I thought he said he already went through them. That's not saying they are good, since most people use a spray can cleaner on them. The only way to make sure passages are open is to dip them and use an air compressor. If that hasn't already been done, that would be my next step.

I'm not a carburetor expert Keith. I defer to you and others when it comes to them.
 
Swanny said:
I'm not a carburetor expert Keith. I defer to you and others when it comes to them.
Click to expand...
I wouldn't say I'm a carb expert either. Maybe trial and error king? :)
 
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