virago only fires on one cylinder

[bstig60]

A compression tester that screws into the plug hole is what you would need and  they will vary in price from $30 to $70 depending on the manufacturer. Avoid the type that has a rubber tip on it and you just press it into the plug hole. They are not accurate. Make sure when you run the compression test that you have the throttle wide open. The procedures are in your Clymer's Manual. Running this test is relatively easy to do.
With only 12K miles on it, I would suspect that all is well with the compression unless you have a valve sticking and/or a ring sticking. Running a good bit of Seafoam through the gas for a couple of tanks after you get the carbs redone will help with that and to clean out anything missed in your fuel system. If you haven't already done so, change your oil to a good quality 20w50 oil for summer riding, (I use Castrol GTX) and then keep an close eye on the oil level for the first few hundred miles.

[GreenHorn1]

Ok, after a year and around $600 it's come down 2 this.  I have a 83Virago 750cc.  The front cylinder was only partially running under 3000rpm, anything over 3000rpm and you could really feel it kick in. It cost me quite a bit trying to fix this problem.  Long story short, I decided 2 pull the carbs out so I did.  I then took the 2 vacuum chamber covers off, took out the spring, the vacuum piston, the jet needle.  I then took paint thinner and proceeded to clean all the tarnish that had built up on those parts. Let me mention that prior to removing the vacuum pistons, they were dirty and didnt float up and down freely.  Now after all the tarnish and gook was cleaned off those parts,  the vacuum pistons moved very smooth and freely!!  I was impressed.  Next, I removed the float chambers from the bottom of each carb.  Again, I cleaned all tarnish and whatever was in there.  Can't 4get this....as i'm doing all of this I also used compressed air and got into all little holes and everything I could without completely taking the carbs apart 2 try 2 clear any passages. Then I just cleaned as much shit from the inside of each carb as I could. Did a good job.  After all is back 2gether, give a good dose of compressed air. Reinstall.  IMPORTANT----Standing over the bike. On your left side along the frame is 2 air breather tubes welded 2 the frame.  One goes to front carb and other to the rear carb.  They are carb intake breathers.  They have little inline screen filters that must be cleaned. My line to my front carb, which was my troubled carb, was completely blocked off, i took it off and used compressed air on it.  Now it's like new! MAKE SURE YOUR CARBS ARE BREATHING PROPERLY A MUST!!!  So now that my carbs are alot cleaner and I solved a breathing problem with my front carb, i'm ready to give it a shot and start her up.  OMG, it fired right away, and the initial throttle response just blew my mind.  I jumped on it and took her 4 a spin right away. Friggin AWESOME, problem totally sloved.  The bike has never run better  and what a response with the throttle.  Everything works like it is supposed to now.  Well I hope this info can help out a few people....it totally worked 4 me.......good luck and if you use this info.......my next project is a very noisy starter......good luck everyone and ride safe!

[skeezix]

I also left this post just now which could be a possible problem as well with the air mixture control valve
http://www.nabble.com/virago-running-on-one-cylinder-td20666994.html 

[texdeb ()]

Going to look at this bike in the am.  I'm pretty sure I will get it no matter what the problem is.  Looks like I have plenty of help in here and my shade treee mechanic bosses.  Here is what the man sent me.  He has already done a lot of work to it but now has ran in to this problem.  After reading your post I tend to think it is the carbs.  No smoke, just problems starting up not that it is cold.  


1982 Virago, 750
I have ridden the bike all summer and it ran great, now that its gotten cold I've been having trouble starting it. I haven't taken it to the shop but there are 2 possibilities, the carbs need rebuilding( they have never been rebuilt) or the CDI is going bad(something virago's are know for).
I think its the CDI judging from the symptoms.

[bstig60]

Once you get it home, try putting 1/2 can of Seafoam in the gas tank, then fill it with gas. Try to start it and get it running until it has enough time to get the stuff into the carbs, then let it set overnight. The next day, start it and go for a ride if you can. If its the carbs, the Seafoam will help to clean them up. Good idea to check the float level before you do this to make sure they are correct or close. If it turns out to be the TCI, (Transistor Controlled Ignition) there is a guy in San Mateo, CA who rebuilds them. Just so you are aware, the TCI unit controls the timing, spark advance and the ignition. So there isn't any timing adjustment on these bikes.

Bill