Motorcycle "back-fires" and often runs on one cylinder

Does the bike backfire only when the throttle is being closed? The carbs have a idle enrichment circuit. If the idle enrichment diaphragms are stuck in the closed position, the bike will backfire when the throttle is shut down. You can't remove these parts for cleaning without seperating the two carb bodies (and then needing to synchronize the carbs after reassembly). A trick that worked for me...fresh fuel, and some fuel system cleaner in the tank...ride the bike at highway speeds for 20 -30 minutes...repetedly rev the engine to a high RPM then shut the throttle closed. The repeted application of high engine vaccum to the enrichment diaphragms freed the stuck diaphragms and the fresh fuel cleaned any gum and varnish that caused the trouble. I've put 20,000 miles on it since then with no backfiring.

Sometimes what sounds like "backfiring" is actually fuel igniting in the exhaust. This typically happens with after market pipes or slip on's. The carbs come very lean from the factory and so the PMS (pilot mixture screw) needs adjusting more to the richer side. If they have not been adjusted they are still hiding underneath brass plugs on the underside of the carb by the float bowl. Carefully drill them out and adjust them out a little at a time. Mine are out at least 4 turns to get this popping to stop. Also your carbs will need syncing after this procedure. A DIY tool is easily built for under $5 if you do a google search. Go here for more information. http://www.sloneservices.com/SilverBack/VStar1100-FAQ.htm

Check for exhaust leaks, a friend had same problem, found and welded small split in exhaust pipe
hope it helps
maddog

Have you double checked the timing?

What type of plugs are you using? The manual says to use NGK BPR-7ES, but these aren't usually available except at Yamaha motorcycle shops. You can use the more widely available BR-7ES, but not BP-7ES, the timing will be off at higher RPM. "R" stands for resistor which slightly delays the timing and produces a more powerful spark. "P" is a projected tip, a couple mm further into the engine.

My other suggestion is to go back to the stock ignition. I had similar problems with my first Dyna 3000 unit which I returned, then the replacement unit worked but the engine just didn't spark as hard as it does with the stock ignition. Although it can't be tuned, the VStar motor runs far better with a stock ignition.

PULL THE CARBS OFF THEY NEED AJUSTING ON THE TOP OF EACH CARB WHERE IT MEETS THE MANIFOLD ABOUT 3/8" BACK YOU WILL SEE SMALL ROUND PLATE DRILL THEM UNDER THEM IS YOUR AJUSTMENT SCREWS SCREW THEM ALL THE WAY IN AND BACK THEM OUT 11/2 TURNS U WILL BE GOOD

The 1100 Vstar (not sure what the 600 has) comes with an a.i.s. that can cause this problem. This is an emissions control system that allows air to be drawn into the exhaust downstream of the cylinder head to ignite unburnt fuel vapor. This may cause some popping or backfiring, especially on deceleration. It's not a problem with stock exhaust, but I will be presumptuous here and assume you went to an after-market exhaust. (or removed the baffles from the stock exhaust) If this is the case you will need to disconnect the emissions system and toss it. Should solve your problem. I was fouling plugs and running rough etc. until I removed this device. Here is a link to more info regarding the emissions system and problems it causes: http://www.vstar1100.com/jack_phelps/vstar/ais.htm

I had this problem on my suziki intruder 1400 only running on one cylinder i put some fresh gas and throttle it rode off and they both kicked in .............runs good now