still have a pop like a vacuum leak

[musclehead]

but I have replaced all the vacuum lines, even the little 2" jobbers on the carbs. new O rings for the intakes, bowl gaskets, and gas lines. I have pulled the carbs out and cleaned  the bowls/jets more times then I can remember, last time they were clear. new timing belts are on their way, ordered last weekend. when they get here I'll install and adjust the valves one more time.

I'm riding it everyday to work and getting about 33 mpg, rode with the wife a couple weekends ago and got 38 mpg. (it's all in the wrist) it probably needs the carbs synced.

[whitestroke]

Do you have pipes?  I put the stock pipes back on and the popping went away.  Well almost, on hard decell going down hill I get a faint popping. I think putting 38 jets would have solved the problem on mine. I'm happy with it quiet though.

[Oklahoma_Valk]

Musclehead,

does the bike pop during deceleration or during idle? Or acceleration?

Sync issues will most definitely cause pop at idle as well as below 3200 RPM while driving.

If it's a sync issue, it will usually stop popping above 3800 rpm or so.


Okie

[Thunderbolt]

If you have had the carbs off a couple of times you probably covered this.  Make sure all the band screws on the intakes are snugged up.  They sometimes are hard to turn, kinda crusted up at the position they have been in forever, until you turn them harder.  How about the carbs with caps on the sync ports, are they sealing?

[salty1]

Turn all your pilots 2 1/4 turns out too richen the lower end a little. Synch the carbs for sure. The bike may still pop some on decel, it's the nature of these beasts. My bike has 6 into 6 Cobras, been desmogged, pilots adjusted, carbs synched, etc. but still pops some on decel at lower rpm.

[97Valk_CT_Euless]

Ended up at 2-1/4 on mine too (Cobra pipes, stock jets with shims added for the needles).  I still get a "Grumble" on decel and a rare soft "Pop", but I kinda like it 

[musclehead]

Do you have pipes?  I put the stock pipes back on and the popping went away.  Well almost, on hard decell going down hill I get a faint popping. I think putting 38 jets would have solved the problem on mine. I'm happy with it quiet though.

still have stock pipes on, boring maybe but I like the wind. it does have bigger jets, I'd have to ask Stuffy what size.

[musclehead]

Musclehead,

does the bike pop during deceleration or during idle? Or acceleration?

Sync issues will most definitely cause pop at idle as well as below 3200 RPM while driving.

If it's a sync issue, it will usually stop popping above 3800 rpm or so.


Okie

pops during decel, and at idle, and below 3200 or so.  hmmm sounds like a sync issue.

[musclehead]

If you have had the carbs off a couple of times you probably covered this.  Make sure all the band screws on the intakes are snugged up.  They sometimes are hard to turn, kinda crusted up at the position they have been in forever, until you turn them harder.  How about the carbs with caps on the sync ports, are they sealing?

4 of thew 6 sync ports were leaking, now freshly capped, the bands on the intakes are all tightened as well.

[salty1]

If your popping at idle, I agree a synch is in order.

[musclehead]

Turn all your pilots 2 1/4 turns out too richen the lower end a little. Synch the carbs for sure. The bike may still pop some on decel, it's the nature of these beasts. My bike has 6 into 6 Cobras, been desmogged, pilots adjusted, carbs synched, etc. but still pops some on decel at lower rpm.

my pilots are only out 2 turns, next time I'm in I'll make it 2 1/4  

[Oklahoma_Valk]

Yep. Most likely a sync issue if it's popping at idle. I wouldnt mess with anything else until I did a sync. Especially since you have stock pipes.

[bogator]

   OK this is a good thread-----before you go to a lot of trouble -----try this ----pipes into block--mite be a little loose----check that----mine was popin a little and I stumbled on the cure. ============GOD BLESS============

[fordmano]

What about relationship to motor or exhaust temps?

Does it happen upon cold start up on choke?
Does it happen upon cold start up off choke at normal idle speed?
Does it happen upon cold start up on choke above 2,500rpm?
Does it happen upon cold start up off choke above 2,500rpm?

Same question only off choke for warm start up at idle
And again same questions is it any better or worse above 2,500 warm?


I am being selfish since mine is doing very close to what you have described.
I was thinking a coil going bad or my Dyna3000 starting to fail. Or exhaust gaskets leaking since mine seems to be ok when very cold and acts up more as everything warms up...