A new miss...carbs or coils?

[LoHo]

I have taken the wire keepers off of the new needles to fix a flooding problem in #3 carb. That seems to have worked. There is now a miss, a slight pop, and my synching has revealed it is in the #3 carb (the vacuum drops when the pop occurs). I don't know if it is still a carb problem or a coil problem. I don't know how an intermittent miss could be a carb problem, but the more I work on this bike, the less I know...any ideas?

[randy]

LOHO,

A coil problem would cause a miss on two cylinders, in your case #3 and #2.

More likely that it's a plug fouled in #3, fouled from the previous flooding? Try cleaning or replacing the plug.

[LoHo]

Yeah, Randy, #3 plug was very sooted up; I cleaned it, but the symptom remains. It was a new plug and has only a few miles on it. I wonder if there might be a plug wire or plug cap problem...

[skids]

Could be, but why would it pop only on deceleration? Maybe that carb's float is too high or maybe the idle screw needs to be adjusted inward a scoush. Will it foul the plug when idling in the garage?

Originally posted by LoHo
I wonder if there might be a plug wire or plug cap problem...

[LoHo]

Skids, that IS in the garage, idling. It isn't deceleration, as I would understand that. It is just an intermittent, soft pop at idle, and #3 loses vacuum on the gauge when it happens. It isn't rhythmical or throttle sensitive. I don't want to take the newly rebuilt carb off again if it is an electrical problem. The note above about the coils affecting two cylinders is helpful; I am glad to eliminate that. I think I'll make sure of my spark plug wire and cap next, to eliminate that.

[randy]

loho,

if you have a timing light, hook it to the #3 wire and if it shows the mis-fire then the plug isn't firing and your problem is electrical (cap, wire, plug).

If the light doesn't show the misfire, then the plug is firing and your problem is carburetor

[skids]

Oh, gotcha. I must have been thinking of my own prior experiences. If it turns out to be a carb adjustment, it will be easy enough. Just try to keep tabs on the amount of rotation for adjustment...just in case that does not work either.

Originally posted by LoHo
Skids, that IS in the garage, idling. It isn't deceleration, as I would understand that.

[LoHo]

Randy, that's a good idea. Pardon my ignorance, but simple electronics works here, right? For instance, if I hook the timing light to the wire, and the miss is a lack of spark, the miss will show up as no light, because there is no spark without the good ground of the plug. Let's say the cap is loose from the wire and sometimes opens the circuit; there will be no spark pulse down the wire because of the open circuit, right? If the coil is sending a spark, but the cap is loose, there is no pulse down the wire, right?

[pathfinder]

Loho, remove the plug cap from # 3 by unscrewing and cut the wire back about 3/16", replace the cap and hopefully your problem go's away.

[randy]

Loho,

That's XS-actly right.

[LoserShoes]

Take the plug out of #3 and put it in another cylinder, and see if the problem follows the plug. Sooty plugs fire across the insulator, instead of the gap.

Steve

[pggg]

Maybe check for a crack or split in the fuel tap vaccuum hose.

[LoHo]

Steve, that is a flipping great idea! After I finish slapping myself around for not thinking of that, I'll give it a try.

[LoserShoes]

Hehe, sometimes the obvious things are the hardest to see.

Steve

[LoHo]

Steve, Randy, Skids, et al, thanks for the help. I switched the plugs and snipped back the wire, and then synched the carbs again. All is now well. I may have the ugliest vacuum advance wiring in the nation, but it works and the bike runs great. Now I can promote a get together, as I attended my last Rally in a Suburban and was shunned by the faithful.

There is no resource like this list anywhere. Where else could one ask a question about a 25-year-old bike and have a dozen replies (and pictures posted, if Talbot is about!) in an hour. What a blessing!