Bike back firing

[firefly12]

I just finished rebuilding carburetors and replaced all the vacuum hoses. cranked the engine up and let it warm up. was fast idling it. When i let off the gas i got some back fires. Any en-site on a possible problem i might be having ?

[Chrisj CMA]

Check all the plastic hoses that connect the carbs to the intakes.  use a little mirror to examine the backsides.  Air leak is a main cause of backfire from either intake or exhaust.

[Paladin528]

Backfiring or popping in the exhaust?

[The emperor has no clothes]

Along with the hoses, check the little vacuum plugs on the intakes.

[firefly12]

all the vacuum lines are new the only thing i did not change were the o rings on the chrome intake

[firefly12]

its more of a loud popping then an actual back fire.  My experience with back firing is one big pop. this is more of a couple loud pops

[Gryphon Rider]

all the vacuum lines are new the only thing i did not change were the o rings on the chrome intake

So you did like Chrisj CMA suggested and checked the backside of the rubber boots that connect the air box to each carburetor, where they connect to the carburetors?

[firefly12]

in the process of doing that now

[larue]

Make sure your exhaust headers are snug

[Steel cowboy]

Did you sync the carb's yet
replace the o rings from the manifold to the heads too.

[cookiedough]

any harm done to anything when letting off the gas having popping sounds coming out of the exhaust?

[Jess from VA]

When I blew the (desmogged) vacuum caps* off the inside intake nipples (where vacuum lines are removed), and the bike backfired LOUDLY on fast freeway decel, I had cage drivers taking evasive action thinking shots were fired.  It was loud as rifle fire.  I don't think it hurt the bike much, but the swerving cages made me nervous.  Was on a long ride home from Asheville NC, and it didn't take long to figure out how to decel slowly to stop most backfire (just don't drop the throttle all at once).

*After I got home, I found one blown in two, and two badly torn.  Those caps were under a year old, but were not up to the task.  Run of the mill auto parts vacuum caps suck, in that application.  The sucking and blowing our fat girls do at that location require heavy duty caps.

[firefly12]

found my problem one of the air intake to the carb was not completely on. Problem solved thanks everyone

[Savago]

Nicely done!

[RonW]

found my problem one of the air intake to the carb was not completely on.

When I installed the rubber boots to the intake runners, I was able to see the back side of the right boots from the left side of the bike and vis-a-versa for the back sides of the left boots. I didn't have to use a mirror. Just a flash light. This was after desmogging ..... without all the air injections pipes and clutter obstructing the area between the banks of rubber boots. That's another advantage of desmogging.

[Hook#3287]

When I blew the (desmogged) vacuum caps* off the inside intake nipples (where vacuum lines are removed), and the bike backfired LOUDLY on fast freeway decel, I had cage drivers taking evasive action thinking shots were fired.  It was loud as rifle fire.  I don't think it hurt the bike much, but the swerving cages made me nervous.  Was on a long ride home from Asheville NC, and it didn't take long to figure out how to decel slowly to stop most backfire (just don't drop the throttle all at once).

*After I got home, I found one blown in two, and two badly torn.  Those caps were under a year old, but were not up to the task.  Run of the mill auto parts vacuum caps suck, in that application.  The sucking and blowing our fat girls do at that location require heavy duty caps.

. Yeah, those OEM caps turn brittle over time and crack.  I use the left over rubber hose from desmogging with bolts screwed into them and they've lasted years.