Left muffler pops

[bakeLit]

My fellow riders,

I have gone through everything (carbs cleaned, float level set, valve clearances set, carbs synched, timing and points gap set, mixture screws 3 turns out) and overall my '81 SOHC bike works fine. BUT the left muffler still pops quite substantially. I have found two tiniest holes in it but haven't got to putting exhaust isolation paste over them. I've also found a similar hole on the right muffler but it doesn't pop at all. Could it be the culprit? Or should I look for airleaks somewhere else, especially on the carb boots? They do seem to have cracks on them, but I'm reckoning they're only on surface. How much can two tiny leaks on a muffler actually make it pop like crazy? Any ideas would be welcome!

 

[xschris]

I would replace the intake manifolds and fix the exhaust leaks. That would eliminate them being the issue.

 

[willem]

spray some brake cleaner or starter fluid around the carbs while the bike is running to determine if those cracks actually suck air in there. Although you should probably replace them anyways, they will only get worse over time.

I had holes in my exhaust which caused a lot of popping. Had my exhausts cut and welded and the problem was fixed

My exhausts do have tiny holes at the lowest points of the mufflers, those should be there. They are there to let any water escape so it doesn't accumulate in the bottom. Don't plug those

 

[Specdog]

Two tiny holes shouldn't cause popping sounds. The usual culprit for our bikes is the crossover tube in front of the rear tire. Get on your back and shine a good light on the entire tube and look and listen for exhaust escaping.

 

[HoughMade]

After you make sure all leaks on the intake and exhaust sides are sealed and are confident the valves are correct and the carbs are synced (as you said), if the problem persists, open the left idle mixture screw 1/4 to 1/2 turn (richen) and see if that does it. All this talk about sealing exhaust and intake leaks is chasing a lean condition which commonly (but not always) causes exhaust popping.

I hate to say this, but as always with these bikes, a clean carb may not truly be a clean carb. I've been there. If upping the mixture helps, I'd give cleaning another try and verify the jets are correct.

Over here (U.S.) the bikes had electronic ignition starting in '80- yours still had points in '81? Wonder why they didn't make the change.

 

[bakeLit]

HoughMade: Beats me, too! I'll try that thing with spraying break cleaner onto the intake area. And those tiny holes ARE supposed to be there after all? And looking at the carbs can't make any harm anyway.

 

[GregT]

un- related, well sort of, I'm un clear as to the use of the exhaust cross over verses a 2 to 1 exhaust and the use of single pod air filters over the stock air intake system. By the way, I'm having a lot of fun with this bike and having rode it except around the block once!

 

[DARKMIDKNIGHTWARRIOR]

The stock pipes are what is referred to as a 2 into 1 into 2 or 2-1-2 pipe. The 2-1 pipes make a little more back pressure and more power than 2-1-2. The pod filters let the engine breath better which is supposed to increase performance.

 

[xschris]

If you stock setup is in good shape I would leave it. You won't see much performance changes by going from 2-1 and pods other than an empty wallet and at lot of questions to the forum like, my bike won't run right or what jets to use? The bike bike will be louder and a bit lighter with maybe 2-4hp increase.

 

[LuckyEight]

2-4hp? It means a lot in my case (27hp)