Carb question, of course!

Hopefully I'll be able to give back some of the great advice I've received someday....

I have one cylinder running VERY lean. So...I tried the air leak test with a propane torch. No leaks. If I direct the flow right into the pods on cylinders 2, 3 or 4, the idle rises as I would expect. But not on number 1. So...here are my somewhat edumuhcated guesses and I'd appreciate feedback.

I suspect maybe a clogged emulsion tube on the main jet in carb #1. That's why it starts and idles, then spits and pops a bit, won't idle wonderfully, won't return to idle all the time, but runs pretty good right around idle. Plug chop shows lean. Meaning it's getting fuel at idle, not off the main. I actually reached in (pod removed) and moved the slide up by hand and did not notice gas. I can feel suction if I cover the carb inlet with my hand, so I think it's pulling through the cylinder, through the valves, etc.

 

Always check the easy stuff first. Make sure your spark plug is good, check to see if you are actually getting spark. (Across your RPM band) Then start lookin for carb help. I always forget to check the easy stuff first!

 

Yeah, I'll check, but it seems that the plug would be wet/fouled if it was getting gas and not sparking.

 

Well....why should I listen to your advice? Just because I asked??? Just kidding, of course. I SHOULD listen.

But, being the strong willed (some call it pig-headed) type, I pulled the carbs and went to work on them at my bench. I should name these carbs, like the guy in "Full Metal Jacket" named his gun, I've had them apart on the bench so many times.

The emulsion tube was shiny clean brass and totally clear. Beautiful. So I checked each orifice and gave everything the once over with carb cleaner while I was in there. Then I put it all back together and tried again. Still no go on that cylinder. So.......I pulled the plug and it sure looked like it could be fouled. Gone was the white tell-tale sign of a lean burn. I cleaned it off as best I could and swapped it with a plug from another cylinder. Now, surprise, surprise, the problem followed that plug. I cleaned it again and the exhaust header does get hot on the cylinder with that plug, but does seem noticeably less quick to evaporate water sprayed on there. It's like it's firing, but weakly. I took it for a plug-chop ride and the "lean" condition reading followed the plug, too. I didn't think that made sense, but I guess that's it.

I'm going to buy all new plugs and see how it goes. I should listen more.....check the easy stuff first!

 

I named mine Larry Curly Moe and Shemp. Moe is #3 , the leader.

 

Ha ha. Now that I think of it, those names are far more fitting than any names I was thinking of!

I'll pick up four new plugs tomorrow and cross my fingers. Other than some minor fine tuning, I think my carbs are cleaned, jetted very close to perfectly and ready to burn! I hope to get some good results from new plugs. Then I can tweak until I'm satisfied.

 

I had that same exact problem a couple weeks ago, and just like you, discovered bad plugs. They were a brand new set of NGK BP7ESs, but I had ran them rich one time and that was it. They were done. I'm running Champions now, and haven't had any problems since. I bought N7YC's, but RickCoMatic said he runs RN9YC's in his bike.