Coil going bad or just the wire?

[Wingnut1]

It seems that the #1 side of my 1-4 coil is putting out spark, but not enough to fire the cylinder. I haven't had a chance to measure the resistance, but does this sound like trimming or replacing the wire will solve the problem or will I need a new coil?

I was replacing spark plugs and boot grommets tonight. When I was finished I started it up and measured the temps on the pipes. #1 was cold, but had a visible spark when I put an old plug in the cap. I switched plug wires with #4 and #1 pipe got hot, while 4 didn't, so I know its the one side of the coil.

 

[SqDancerLynn1]

Your testing leads me to believe you have either a bad plug cap or bad wire.

 

[TheCafeKid]

The coils don't work like that. The one coil fires both plugs 1-4 at the same time. It's more or less a wasted spark system. The other coil fires 2-3 at the same time. You can't have a half bad coil. It's more than likely your plug wire. Is it making good contact? Change the caps trim off a 1/8" or so. Those stock wires are stainless steel core, so they usually don't go bad unless they're simply broke.

 

[Wingnut1]

3 cylinders fine, 1 cold

3 cylinders fine, 1 cold

#1 is still running cold. Could it be something in the carb? For a bit yesterday, I had no spark at all and wiggled the wires near the ignitor and that fixed that. Then I cleaned all the ignitor connections and checked continuity up to the coils. I have measured the resistance at both ends of both coils and the lead going to the signal generator, everything is in spec. I replaced the wires from the 1-4 coil and bought 2 new caps, currently on 2-3. I've moved plugs, caps, coils and tried old and new plugs. I measured the original caps and they all have the same resistance. Sometimes changing plugs wires between 1 & 4 makes no differance, sometimes it does.

I have a 1 volt drop at the coils compared to the battery. 12.5 at battery and 11.5 at both coils and 2-3 work fine.

I checked compression (130 psi, 200, 160, 170 for 1 to 4 @10:25:1 1,066 cc's) #1 was cold. Checked valve clearance (good) looked at cam indexing (perfect), and bypassed the fuel filter. In March, I dipped the carbs and replaced the O-rings. Pretty sure I would have measured exhast temps between then and now so all was fine for a while.
It idled great then, right at 1,000. When I cleaned them I couldn't get the air screw out of number 1, so I didn't get that in the dip.

Am I right that any problem with the signal generator, ignition module or coil would affect 2 cylinders?

I took it out for a test spin and it wouldn't get above 5,000 rpm. Started running afwul around 4K. Trying it last night in neutral without the fuel filter or air cleaner it would get over 5K, but RPM's would increase & decrease between 5K & 6K without any change in throttle postion. I'm not sure if its weak spark or a dirty carb. It doesn't idle much at all below 1,500 or without the choke on.

I guess next I'll check for leaks at the intake and see if I can get #1 carb off for cleaning without having to take the whole rack off. I hate that. What else?

Thanks,

 

[Wingnut1]

Its Fixed

Its Fixed

Seems to have been the stator connection. Last year the plug was replaced with 3 sets of terminals. Those were looking a litle rough and I noticed also quite hot. Replaced them and all is well.