Topic: 1979 cb 650 popping missing Im pulling my hair out!!

[Thor0812]

Got a cb 650 4to2 pipes, pops out of left pipe at idle, acceleration, deceleration etc etc. I have adjusted valves, cleaned carbs, changed plugs, switched plug wires(to see if the pop moved). It is also cutting out. It is very noticeable in 5th gear but it does it in all. I thought maybe timing but it is only on the left side???
HELP!!!! This is driving me nuts!!!!

[tonycb650]

you may have a burnt exhaust valve.

[dummkauf]

Don't know what your bike looks like but it could be possible there's a hole or break in the pipe.  Only saying this since the exhaust on my Buell broke right next to where it bolts onto the engine during my ride home from work today and aside from being very loud, it was sputtering and back firing since the air was blowing straight into the hole. My theory being that a hole somewhere could allow air to get in causing the back firing and sputtering but might not be big enough to cause the bike to be too loud, which could also explain why it is worse in 5th gear since I am assuming that you are going the fastest in 5th which would lead to more air going in.

Note that I am by no means an expert though, I'm sure some of the others on here may be able to offer more advice as well.g

[KingCustomCycles.com]

you may have a burnt exhaust valve.

perform a compression test

[Thor0812]

Dont have a comp tester. Anything else I can look for?

[speedy gonzalais]

remove the plugs check colour to see if rich/lean or clean the plugs run the bike then check them if ones not firing the plug will still be clean as for compression romove the carbs turn the bike over with none of the plugs connected hold your palm over each inlet you should feel sucking on all

[coyotecowboy]

Dont have a comp tester. Anything else I can look for?

Yeah, look for a NAPA and buy a compression tester

You also might make sure your carb manifold boots are sealed up tight.  Take a can of WD40 with the red straw and squirt around your intake boots while its running.  If it speeds up then you have a vacuum leak somewhere that you have to find.  I had one of my carbs loosen upon the manifold plate once and start sucking unmetered air.  Took quite awhile to find that one.

[Hush]

You don't tell us how long you have had the bike or if you have only just put it back on the road?
Did it run sweet before this or is this "popping and farting" the only way you have known the bike to run.
I have a 79 650 running 4 into 2's and mine has a similar problem but I'm putting it down to the carbs needing to be synchronised, have your carbs been synced?

[Skonnie Boy]

I had a persistent misfire, which was not cured until I synched all the carbs and cleaned them.  I caved and bought a carb synchronizer.  $75 well spent, in my opinion.  In my case the misfire was just the #4 carb drowning the cylinder in gas.  Ditto on the compression tester, too.  They can be had for $30 or less.  Not a bad price for diagnosing or ruling out serious problems with the engine.