Topic: cb550k pings and pops upon revving... (updated with video)

[___aLovelyAntihero___]

___updated with video____

I have a rather strange problem with my 78 cb550k maybe one of you could help me diagnose.
The bike will start up just fine, idle at the normal level & warm up for about 2-3 minutes, then it will pop (not so much like a backfire pop, but more of a metallic ping) & then idle up to 3000 & begin running poorly, complete with backfires & pings. If this happens when i'm riding, the bike becomes impossible to ride. The second cylinder from the left (when viewing the bike from behind) seems to be causing the issue, as it is the one visually backfiring.
The fuel system has already been completely gone through, & plugs & wires appear to be fairly new.
I'm sure the answer is obvious to you guys, but I'm just a stupid lost kid. Valve adjustment? Timing off? Electrical? What I don't understand is why this only happens once the bike has warmed up.
Help me please...

[cb550inct]

are you running stock exhaust and carbs?

[TwoTired]

Totally stock bikes shouldn't do this.  Is that what you have?

Status of the routine 3000 mile tune up check list?
Had the motor been apart?  Head off, cam cover reinstalled?
Compression check results?

So far, with information given, I suspect a bent valve.

[___aLovelyAntihero___]

Thanks for your help, guys...
The stock mufflers have been replaced with 4 individual custom mufflers (no idea what kind, came with bike) &  the carbs are stock except for custom filters. Motor has never been apart to my knowledge, & I have not performed a compression check... I was just in town for a day for my grandfather's wake & did not have time to mess with it.
If a bent valve is to blame, could i get away with only replacing the valves in the problem cylinder, or is it better to do them all? Money is a huge issue....

[TwoTired]

Status of the routine 3000 mile tune up check list?

Tappet too tight might be cause.

[___aLovelyAntihero___]

Hey guys, sorry to drag this back up, but I'm on vacation and able to finally get some work done on this bike. I really really REALLY want to get her on the road this summer! I went thru the carbs again, turns out the plungers were all out of sync with the main carb... my rookie mistake for not holding the set screw while tightening down the nut. This has solved the revving up upon warming up issue!
I was about to celebrate, when the pings and pops returned....
This time, i was able to take a video, they are kind of difficult to hear, but perhaps one of your more trained ears could identify the problem?
 
http://youtu.be/PiAlsI9UOyU


I really do appreciate all the help, guys...

[strynboen]

get? all 4 pipes varm..think one  is missing..firing

[TwoTired]

Have you vacuum balanced the carbs?

Have you made any compensations in the carbs for the pod filters?
what is the status of the routine 3000 mile tune up check list?
Had the motor been apart?  Head off, cam cover reinstalled?
Done a compression check?

[grcamna2]

Have you checked if you have decent ignition points and condensers and is the timing set correctly ? 

[Tews19]

What are those pod looking white foam thingy in place of the stock airbox? You ever think about going back to the stock airbox? LIsten to TT his advice is always spot on.