I have recently acquired a 1994 Dyna from a friend who passed last year. He had owned it for at least 20 years. I know it's not 1340 anymore. I know he had it bored, piped. Maybe valves and ports, I'm not sure. I'm sure he told me at one time, but I don't remember.(I never planned on owning it ya know?) I contacted the shop who did the work. He remembers doing the work on it, but it has been so many years ago he doesn't remember what he did. It was before he had a real shop and kept records.
So, I have gone all through the carb, cleaned every jet and port. Ran carb cleaner through it for about 100 miles. Changed all the intake gaskets. Same problem.

It backfires really bad.

It will sometimes backfire between gears, but always on decel. Experience has told me that this is usually beacuse it's too lean.

This is what I have found. It has the original 40mm Keihin carb. The air screw is still factory capped. The original jets were 165 and 42. The main has been changed to a 195, but the pilot jet is still a 42. Could the 42 pilot be causing the backfire on decel? At that point the main would be closed and the fuel would only be coming through the pilot. Since the main had to be changed up 30 points, shouldn't the pilot be changed up too? And by how much?

For info...I"m in Bakerfield, CA. Elevation 300ft. Usually ride up to 5000 ft elevation at most.
Thanks for your help.

 

My '93 has headwork and is .010" over.
180 main, 45 pilot, and barely pierce that air screw cap, use a sheet meta screw to pull it out. Seat it lightly, then back it out 2 turns, open it 1/4 turn at a time until it's good. More than three and the pilot jet is too small. Works for me.
Also, check the intake manifold for leaks, and start with fresh plugs.

 

Coughing & farting through the carb is the usual lean condition and through the pipes most times is an exhaust leak but since you've been into it recheck a few things.

Do an intake leak check at an idle while the bikes warm, take a can of brake clean with the little tube on there and give it a few short shots around the head ports, lastly check the pipes at the heads a loose one will cause the backfiring too

Lastly off pop the cap on the mixture screw and run it out a full turn while listening at an idle when it starts flubbering back it off a 1/4 turn or so

 

Something seems amiss here. All that work, and no one has ever set the idle mixture on the carb? Seems odd. Makes me suspicious of the skill level of the guy who worked on the engine.

TwiZted is right on the money. Make sure nothing is leaking first.

Once you are sure the intake and exhaust are tight, I'd do a full rebuild on the carb (ie, replace all the soft bits). Then go through the standard carb tuning steps. It's not rocket surgery.

 

Make sure the plugs are good. Heavily carboned can cause a misfire. Easy to check and clean and re-gap

 

Put a Mikuni 42mm on it.
You'll love it.

 

As others have said, check for intake and exhaust leaks first, but all my carbureted Harleys have HAD to have larger pilot jets. Popping and belching back thru the carb at low speeds are definite signs of lean (pilot jet too small). I would recommend going up on the Pilot for sure and drill out the adjustment plug to get at that air screw, it must be adjusted to get it right. 195 main sounds too fat imo, but without knowing what been changed, impossible to know without being there. The stock carbs are great and cam be reworked into hi performance applications if you know how to tune them.

 

Sometimes good to "zero it out"...meaning, reset all the adjustment screws to base...and then follow the factory guide to put them to default/stock settings. And then tweak from there.

Due to different people "fiddling" with the carbs...over time they can get quite out of whack.

 

try 185 & 48. the above advice on the idle air is right on.

 

That's what I was thinking. Down on main, up on pilot. It runs great going down the road, very responsive, no lugging.

I really appreciate all the help guys. It's nice to find a forum with actual helpful people. All of you seem to be on the same track, that's always helpful. I ordered a jet set with 3 pilot, 8 main, and 2 rods. I'll knock out the mixture plug and play with the jets. I will let you know what works.
Thanks guys!