My 2001 Shadow Aero 1100 has been backfiring on decel since I purchased it back in April.
I did notice when I was travelling between 60 to 70 MPH and gave it more throttle it would sputter, so 2 weeks ago I took it to a bike mechanic. 2 weeks later he called and said it is ready to be picked up.
When I picked it up he told me he had changed the jets from 175/180 (stock jets) to 180/180 and rode the bike. The bike still did not run correctly, so he replaced both jets to 185/185 and the bike still did not run good. He then put in 175/175 jets and turned the A/F out 2 3/4 turns and the bike ran well, but now has a back fire on decel.
The bike does not run out of steam or sputter while accellorating, but has a lot of backfiring on decel.
My question is.....could the A/F mixture setting be the cause of the backfiring?
When I first got my bike it had lots of backfiring and popping on decel. My problems ended up being a combination of things. The carbs needed cleaning, the carb boots were leaking and the crush gasket on the front cyl was leaking. After fixing all of that I still had the popping on decel and ended up changing the pilot from a stock #42 to a #45. Have not had a single backfire since, and I've had the bike pop on decel 1 time since. (it has been several months, over 1,000 miles ago)
Hope something in here helps
p.s.-- is it backfiring or popping? there is a difference
When I first got my bike it had lots of backfiring and popping on decel. My problems ended up being a combination of things. The carbs needed cleaning, the carb boots were leaking and the crush gasket on the front cyl was leaking. After fixing all of that I still had the popping on decel and ended up changing the pilot from a stock #42 to a #45. Have not had a single backfire since, and I've had the bike pop on decel 1 time since. (it has been several months, over 1,000 miles ago)
Hope something in here helps
p.s.-- is it backfiring or popping? there is a difference
On decel it makes some what I call somewhat quiet popping and then a loud what I call a backfire, sounds like a shotgun going off if I am near a brick or metal sided building.
Sounds to me like you are in the slow jet area of tuning. Someone with more experience may be able to protect you from what I'm about to say, but here's my .02 with change.
Think of it as the slow jet has two circuits. One is assisted/also regulated by the idle screws while the other is controlled only by the slow jet orifice. As the throttle blades close, they divert the limited amount of air past the idle circuit opening in the bore of the carburetor. The amount of fuel fed to the engine at this throttle setting (idle) is very little, and is controlled by the idle screw(s). As the throttle blade is opened, the idle circuit's control of the amount of fuel is shared with the slow jet, via other circuits within the carb bore.
I noticed that I could turn the idle screw out so I didn't have popping/backfiring with the throttle blades totally closed (idle) but if I rode along in 2nd or 3rd gear and closed the throttle slightly (not totally), the bike would backfire. That lead me to believe that my slow jet wasn't delivering enough fuel, while the idle screw circuit could be opened up enough to supply the very limited amount needed with the throttle blades closed.
I swapped out the stock 42 slow jets for 45s, and all of the popping went away. Plus, my idle screws don't need to be screwed as far out. Something to consider.
Do you have an aftermarket air filter or exhaust installed on this bike? I agree with C5rider in that you have a lean condition in your slow (pilot) jet circuits. You do have some room to back the A/F screws out some. Try a half turn out each from where you have them at 2 3/4. If that doesn't help get larger pilot jets.
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