Okay, stupid question done to death, but here it is. May the carb gods be kind.
Still chasing an intermittent backfire. Just got back from a 60 mile test ride. On this ride I noticed if I didn't close the throttle all the way between shifts, the POP wasn't present. At all other times it was intermittent. Hard acceleration, sometimes. Short shifting, less frequent, sometimes a POP POP. Decel, jake brake-like with occassional crackles and sometimes a weird sounding POP. None of these are consistent except the one where I don't close the throttle all the way between shifts. It's close to being all the way. If I would put a pencil mark on the throttle handle and switch housing, the measurment from fully closed would probably only be about an 1/8th inch.
Now, my question finally, will shaving the white spacer a little more help this? I think taking the tank off is a pain in the butt, so I'm seeking opinions first.

I just rebuilt my carb and battling the same problem.  I shaved my spacer about half way and today I was tweaking the mixture but I, too, have a random backfire still.  I think mine is an exhaust leak, though, because my sportster muff isn't sealed 100%.

But tweaking the mixture did make significant differences in how often and how loud a backfire I get.  So maybe I'll eventually find the right spot for it.

if you replace your stock carb screws with allen head (s.s. better yet)screws  you can lossen the carb at the boots and rotate to do your carb work without removing tank...

I can't take credit for this, but using that "Muffler Repair Wrap" around and between the pipes (at the joint) seems to make a great air-tight heat-proof seal. It worked for me.

JerryAssburger wrote on 12/31/69 at 16:00:08:


Maybe I used a different brand or something but I tried that a couple of years ago and it wound up just burning off.

Well it wasn't maxed. I set it by turning in til the idle slowed and out til the idle slowed, and the happy middle ended up being 1 1/2 turns out. Ran great there except for the occasional POP.
I took your advice and set it to 2 turns out (exactly where the idle starts to slow) when I got home from work. Then went for an 8 mile ride with a lot of shifting. Seems to be a little better but not as much power. Still POPS between shifts but didn't seem as often. I think I'll leave it there for a few days until the new header gasket comes in. Am I being too much of a perfectionist or can I really get rid of these POPS?

Guido wrote on 12/31/69 at 16:00:08:

Sounds like it maybe out a touch to far and perhaps sucking some air either at the exhaust or the intake tube - on the mixture screw - when you get it close you need do 1/8 turn adjustments or less to fine tune that baby in

Also, Reelthing, it says your running a 155 and 3/64ths spacer on an 02. How does that do? Any backfires?