My mileage was into the 60's before all my mod work, with most riding on the street around town with very little trail time. After mods, I've been running 40 to 55 mpg, but my gearing is 13/49 most the time and we run lots of slow single track where average speed is 10 mph or less. My fuel/air screw is out about 2 turns and with the stock #35 pilot jet. But you should not set your fuel screw to my setting...it should be set for what's best for your bike/elevation/mods etc (read up on how to set your fuel screw by idle speed). Mine pops too, which I'm attributing to a leak and the header/muffler point that I haven't sealed off yet. Maybe it will pop even after the leak is fixed? Are you thinking the HMF may be some culprit to lower mileage? Could be on to something, dunno. What size pilot jet? Did you change it? I had a #38, went back to #35 and mileage improved (it was RICH).

 

I didn't mess with the pilot.. only main (128)
I have my fuel/air out to 1.25..
I also have the lid off the air filter..

Does fuel/air have anything to do with popping?
(i am a carb super noob)

 

Yes, it can, and it can suggest lean idle-position (closed throttle) conditions. And I think I've read others suggest it could indicate a rich condition, but not sure of that. But, if there is any air leaking into the exhaust, it can pop even if jetted properly. I've heard that a little decel popping can be normal. Check for leaks. Plug the end of your exhaust and listen for leaks. If it's not too hot, maybe spray a little soapy water around the connections to see if it bubbles. If the bike doesn't stall when exhaust plugged, you got a leak.

 

Good call! I appreciate the help..
In theory if I turn the fuel/air screw out to 1.5 will this help the popping..
Popping occurs because of lean mixture?

 

Yes, in theory, but 2 or 2.5 turns may be even better. You may not see any benefit at 1.5 and need to go further out. But silencing the popping with your fuel screw isn't necessarily the preferred way of setting the fuel screw to the best position. Yes, lean can be one reason for decel popping.

I've adjusted my fuel screw by turning the idle speed up a little (around 2000 rpm), then adjusting the fuel screw to the highest idle by starting at about 1/2 turn out and turning outward noting where the idle peaks, then turning it back in about 1/4 turn from there (leaning just a bit), then turning idle adjuster back down to an idle I like (about 1400-1500 rpm).

 

I am going to try that!
Thanks again.