Slight black exhaust smoke on idle 56 flh

[pete baildon]

G'day fellow Pan owners and riders alike,am new to the community and my first thread...Hope I get this right so we'll see.Have sorted and checked many things on my 56 from imfo I've read here and different opinions have helped and enlightened also.I have a few issues with my pan that I'm sure can be improved so I'll start with tuning and sort that first.Firstly the engine runs great and is easy to start.It was fully rebuilt 300 miles ago.It is a standard 1200 with no internal mods.The carb is an S&S and perhaps this is where I need some education!I'm no mechanic but have reasonable knowledge and have tuned it by ear and ridden it and adjusted the mixture and am pleased with how it runs idles starts etc.So I cant understand why when I start it and reduce the choke to zero and its idling smoothly why it blows black smoke slightly...When i increase the revs slightly it runs clear,some tuning advice needed there! All plugs and points to spec and running 60wt oil.Look forward to some enlightenment...PB

 

[Breeze3at]

Welcome to the forum Pete. I'll throw out a couple of things that may help/explain. It sounds like you have adjusted your idle air mixture by ear. Try backing it out just a little more and see how it is. I have a shovelhead with a distributor, is yours a mechanical advance distributor (not left grip)? Mine blows a little black smoke at idle, and I believe it is because the timing at idle is so retarded the fuel does not have time to completely burn. Just off idle the advance kicks in and it burns better. Kick only ignition systems have to be quite retarded to start without kickback. That's also what makes them sound so good at idle.

 

[Jack Klarich]

Welcome to the forum Pete. I'll throw out a couple of things that may help/explain. It sounds like you have adjusted your idle air mixture by ear. Try backing it out just a little more and see how it is. I have a shovelhead with a distributor, is yours a mechanical advance distributor (not left grip)? Mine blows a little black smoke at idle, and I believe it is because the timing at idle is so retarded the fuel does not have time to completely burn. Just off idle the advance kicks in and it burns better. Kick only ignition systems have to be quite retarded to start without kickback. That's also what makes them sound so good at idle.

My 60 FL was the same way, I would run it a tad rich that would account for the black smoke, it seems to me the older motors had no valve seals, this would explain some of the smoke also

 

[pete baildon]

Thanks Breezy and Jack,doesnt sound like its too much to be concerned about and after experimenting with idle screw it didnt seem to change anything except the way it idled,so i put it back to where it was.The dizzy is not mech' advance and dont think I want to play around there too much as it starts and runs so well where it is set now.I think its the timing at idle and technology of the era as youve explained and many thanks for your input.have a few other minor issues that I will address after work this evening,have a good one...PB