What's this noise......???!! Video attached..

[Snikare]

I've been toying with my motor and my carbs. Everything is in great condition. I've put new jets in the carbs, Cleared out the everything. Checked and tolerenced the valves, played with the timing to fine tune it, and everything is on a new build.
I just went for a ride this morning after getting a bunch of work done to the carbs again, and it was running beautifuly. Right before I got home though from this short ride around the neighborhood, I started hearing this popping sound, same popping that has eluded me for a long time now. I played around again with the mixture, and the timing. But nothing seems to be fixing it.
Can someone diagnos this popping for me?

Check out the video here-

 

[Snikare]

It seems to be only coming from the right cylinder...

 

[Snikare]

I've been doing some more work on the bike. I've redone the timing marks again, and then timed it. I took off the headers and sprayed the valves and inside of the combustion chamber with carb cleaner to clean out the junk... Then srayed the tops and the bottoms of the valve seals with Aero Kroil and Marvel Mystery Oil to try and relieve any stickiness. I addedSeaFoam to my gas and a bit of Marvel to my engine oil. I let it run for a while to burn out the excess fluids and flush my system, then I shot Carb cleaner up through both carbs to try and get more gunk out of the combustion chamber and off the valves.
This proved to do a lot of good work in cleaning things, but it did nothing to improve the popping.
Check out the sound I'm still getting:

I'm also finding that no matter what I do with the timing or the mixture, My timing and idle tends to fluctuate quite a lot. It will run smooth for a bit and then speed up a little, then drop back down...

Any help anyone can provide as to where I need to go next, would be greatly appreciated!!!

 

[weaselbeak]

I bet that with a full exhaust system you'd never hear anything. Might check the header gasket for leakage, but my guess up front is an unsteady fuel flow causing a lean condition. Have you tried getting it right using the idle mixture screw?

 

[Red Beard]

Maybe very slight lean misfire? check fuel mixture screws and carb sync, pull your plugs and see what they say, if your unsure post pics of them, that might help in diagnosing too.

Also what octane gas are you running?

 

[Snikare]

Thanks for the replies. I have of course done all those things. By masking the pop with a full exhauset, you aren't actually fixing anything though, you're just hiding it. So I'd rather actually fix the problem rather than cover it up... I've most definitely played with the jetting and the mixture screws, also tried synching the carbs and adjusting the timing. I've checked all electrical components, and even cleaned and checked my fuel system as well as the combustion chamber and valves. Nothing has changed the popping. The plugs look a little fouled as if it's running too rich in that cylinder, but just barely....
I'm running high octane gas. I've even added a good amount of seafoam to the last tank.

I've finally broken down and taken it to a professional. He's diagnosing what the problem could be. He too is so far a bit stumped as to what it may be given all the work I've done to address it... Any more thoughts would be welcomed.

Thanks again.

 

[Red Beard]

Did you pull your spark plugs and compare how the right side looks compared to the left? Or how they both look in general?

 

[Snikare]

Yes. The plug on the right cylinder looks just a bit fouled. the one on the left looks good.

 

[Red Beard]

Hmmmm strange for it to be running slightly rich and backfiring or popping......

How is the cam chain?
Im curious about the valves on that right side, were they pretty out of wack when you adjusted them?

 

[Snikare]

The valves on the right side were well within tolerance, both of them were for that matter. The bike had sat for 28 years, leaning on it's left side. It worked perfectly when it was parked, and then by the time I'd gotten to it, it needed some TLC... That's it in the profile picture.

There is a small amount of carbon on the valves, and on the inside of the cumbustion chamber. However the pressure is good. The bike has 10,000 origninal miles on it. I've done a complete Tune up and rebuild, up to any removal of the head. Carbs are fully rebuilt, holding #35 Pilot Jets, and #140 main jets. The needle was lowered 1 clip, and the mix screws were set to 3 turns out, respectively. The carbs had a bench synch when they were off. And they have shown to be at a good place for performance.

The CAM chain I haven't seen directly, but from the adjuster, it looks to be in good shape, and I don't feel a big amount of play in it while I'm turning it over by hand. So I'm assuming it's decent. It doesn't present any noise out of the ordinary while running.

 

[Red Beard]

Well I'm stumped, that is a pretty weird little pop for sure.

 

[Snikare]

I took it in and my mechanic found it. I had rebuilt the carbs, but then in putting it all back together, I had a new gas tank, and new tank liner, on top of no fuel filter. Something had gotten through and plugged up the right carb. We got it all re-rebuilt, and cleaned with new filters.
It's good as gold now. Ran beautifully on the way home.