Re: virago running on one cylinder

Hi.
I've found a few helpful members on this forum       http://viragotech.com/

I have an 81 750.  Had similar problems, and there are many others who have experienced this issue with the front cylinder.  One of the best reads had to do with vapor lock.  I personally have experienced this after a ride, when I park on the side stand, which leans the bike to the left.  There is a breather tube from each carb which I understand runs under the tank and through the frame.  It can become clogged causing something called "Vapor  Lock"   One guy said he uses a bicycle cable to run through the tube making sure it is clean of any little bugs or whatever.  This seems to have helped a lot of riders.   I'm going to try it.

I've always wondered if the tilt of the bike had something to do with the front cylinder problem.  
I'm pretty sure it has also happened more after a rain when the bike was left out.  I wondered if water was  finding  a low spot such as the plug hole, or possibly the wire connection to the coil.  It seems one of the two coils tends to rust much more than the other.    Certain weather conditions could be encouraging condensation too either clogging the tube at a low spot, or some other location where it can gather.  

I'm also looking at all the electrical connections such as up inside at each end of the plug wires as there can be corrosion that cuts down the amperage or voltage reaching the plugs.   The Virago has a weak spark to begin with.  One guy explained that as the starter is running it's even weaker.  The right plugs are really important on these bikes.  It seems the non-resisting type are needed.

I pulled my carbs off, but haven't reinstalled them.  I dipped them - soaked, thinking that might be the problem.   While I was at it, I ordered new bladders for the petcocks on ebay and installed them.  

Another weak spot with these bikes seems to be the vacuum system.  They are prone to leaks.  Leaks can happen anywhere along the system from the petcock, which requires vacuum, along all the hoses and connections.  Also at the carb inlet, where I noticed my O ring was broken when I took it off.  I still believe the left side - front cylinder side tends to be more prone to these types of issues related to condensation or moisture finding  a low spot.  

Another guy mentioned that some of the gas additives such as ethanol are deteriorating the rubber orings or fuel valve seats not allowing it to close properly.  My parts supplier said he got a spike of orders and thought it might be the fuel.   Those are the valves that close when the float rises .  if it doesn't close, fuel keeps flowing and will overflow.  You will see a little leak.
Many forum writers talk of how important it is to set the float level properly.  I don't know how they would get out of place, but there is a little sheetmetal tab that has to be bent so it touches the valve properly when it rises and pushes it closed.  I suppose it can, over time be bent by a sticky valve, or just from wear and tear.  repetitive movements pushing against it.    But the more common problem seems to be the opposite of a float that isn't high enough.  You can put a clear plastic tube over the drain, let fuel in, and turn the tube up to see where the gas level is in the carb.  They have to be level.  The correct level is 1 mm above the bottom edge of the top section of the carb where the bowl attaches to it.  The only way to get it right is to use trial and error, which requires removing the bowl.  Many make special short screw drivers, or replace the screws with allen screws and use a short allen wrench to make removal easier.  I plan to do this on the bench before reinstalling the carbs.  
Good luck.  I'll check back to see how its going.  I'm not a mechanic, so I'm just learning too.
ggogan@gmail.com