Hi guys, me again. I've been tinkering with the bike and found that the air/fuel mixture screw on the right hand (brake side) of the bike doesn't affect the running of the bike at all. If I screw the one on the left side (clutch side) the bike will die but with it idling I can screw the right side screw all the way in or out and it does nothing. The bike still backfires on deceleration and now it does the same on acceleration. I have sync'd the carbs and tried setting mixture screws at 3.25 turns each (i have aftermarket Vance & Hines exhaust) Even when the right side screw is all the way in it appears the front cylinder still fires after you turn the throttle a little way. it doesn't appear to be firing at idle.
It sounds like the idle mixture needle on the right side might be damaged or the seat on the side might be damaged. With the bike off unscrew the one on the right all the way out and inspect it for damage. The other possiblity is that it might not be a problem with the idle mixture, it could be a problem with the mid or high section of the carb the is allowing gas to enter the carb at idle.
One of the problems with Vac gages is that they can get out of adjustment, they need to be hooked to a common manifold with a given amount of vacuum (needle in the center of the gage) applied to be sure they both read the same, there's a adj screw on the back to adj it with.
double checked carb sync and I even cross checked the gauges to make sure they both read the same. adjusted it a little but they were spot on afterwards with no change. When you put your hand over the exhaust pipe for the front cylinder you feel cold air. Does that mean fuel or spark? I switched the coils and the bottom cylinder acted like it wanted to fire with the choke on but at normal idle still nothing. Should I continue chasing spark issue's? could it be an ignitor and if so where are they located and can they be checked? Or are we still looking at carb problem?
Is it running on 1 cylinder? if it is then when you switched the coils it would mean the coil is good and it's a fuel problem, did yo check the diaphragms on the slides?, if there's even a tiny hole/crack it won't want to lift like it should.
it is running on 1 cylinder. I have confirmed that full choke makes the front cylinder try to fire which tells me it's starving for gas. The bike did sit up for awhile prior to me buying it so the carb is probably dirty. Tomorrow I'm going to put it back together and take it for a long ride with some MMO and B-12 in the tank and see if it will work it helps. If not, its time to take the carbs off for a good cleaning. I'm a little nervous about doing that which is why I'm trying everything else first.