Motorcycle Repair: !975 Honda 360T putt- putt from left side muffler, honda 360t, side muffler

Question
Hi Chris:
 I finally have my 1975 Honda 360T back together and it starts fine, runs good, but the left side muffler is giving an occasional "putt-putt". It is not a backfire and the bike will run and idle good, but then there is this putt-putt sound coming from only the left side muffler, like it's missing a little bit. I did patch a few rust holes in the muffler but they seem to be fine. The carbs have been soaked and all jets were cleaned. I have installed new spark plugs. This engine ran fine on another bike and I'm wondering if it could be the coils. The set I'm using now are not the same as when the engine ran without this problem. Also, the headers and mufflers are a different set. Do you think this could be a coil problem? I still have the set from the other bike. The bike starts at the touch of the button. Hope you can advise me on where to look for this problem. Thanks, Ralph rljones@columbus.rr.com

Answer
Hi Ralph.

 It could be a problem with the coil, but I would go back and make sure that the valves have been properly set before you change coils.  You could have a valve timing issue in the one cylinder.  The one exhaust valve could be just off enough to not be properly timed.

After that, check the coils as per the testing proceedures in the repair manual.  If all of that doesn't do the trick, then try using the original coils, if you can and see what it does then.

Good luck and ride safe.
FALCON