Motorcycle Repair: yamaha vx7, plug colors, fuel stabilizer

Question
I've currently purchased a 84 yamaha virago.  On my registration paper it is designated as model VX7.  Does it have a 699cc engine or is it the 748cc engine. How can I find out.  Also I just had it sertviced and the engine seems to be running smoothly but it does make the occasional sputtering noise.  My mechanic said it will go away once I put premium fuel in it.  will it help or do I have a more serious problem?  This is my first bike so any help would be greatly appreciated.  Thanks

Answer
Hi Walter,

Your bike should be an XV700 by the sounds of it.
The XV750 was not made in 1984 just until 1983.
The 700 was made until about 1987 and the
750 resumed production about 1988-94.

It can be very confusing.
If you send your VIN number on the frame
I may be able to get more info for you.

The sputtering may go away with some use or
maybe some good fuel. If not, carbs may need
cleaning or air filter could be clogged.
If normal tuning doesn't help then check
the spark plug colors for clues on the problem:
http://verrill.com/moto/sellingguide/sparkplugs/plugcolorchart.htm

Make sure the choke is not on.
Infrequent use can clog the carb jets
so add a fuel stabilizer if you plan not
to ride often. Auto parts store or even
Home Depot may have this additive.

Keep the battery up with a small 1 amp
maintenance charger as the charging systems
on bikes are generally weak.
http://www.amazon.com/Battery-Tender-021-0123-Junior-Charger/dp/B000CITK8S/ref=s...

The bike will run better with a strong fully charged battery.

Have fun!

Wayne S.
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