Motorcycle Repair: poor accerlation, fuel stabilizers, float bowls

Question
Hello Chris,
    I have a 1988 Yamaha FZ600 that I purchased a while back and it was in a million pieces when I got it.  I took a year and rebuilt the entire bike and I am proud of the job.  The bike ran very well last year but when I went to get it out this year it did not want to run correctly.  On the petcock there is three settings on, pri, and res.  What setting should it be on when you are riding the bike.  The bike will only accerlate when you have it selected to pri.  Please let me know if this is the setting it should be on or not. I can look at the clear fuel filter and fuel only seems to flow into it when it is selected to the pri.  The bike will run on the on selection but after a while it seems as though it runs out of gas and won't acclerate.  Please let me know what I should look for and what setting the petcock should be in.  I did you fuel stablizer in the tank before I put it away for the winter and I also changed the plugs and oil before I was getting it ready for this season.  Thanks for your help. Ron

Answer
Hi Ron.
 Well, the petcock should be set to the 'on' position. Fuel petcocks in modern foreign bikes (1970 - today) have 3 settings, normally.  they are 'on', 'res' (reserve) and 'pri' (prime, which is used only when the carb float bowls are empty and need to be primed prior to startup).

The fact that it isn't running except when in the pimer position is a bad thing.  You could have a leak in the vacuum line from the petcock to the manifold or you could have a bad valve.  Cleaning the valve may help in this case.

A word on fuel stabilizers; they do not really work.  The best thing when storing a bike for the season is to drain the tank and burn off all the fuel left in the floats.

Alternatively, you could run the bike for a few minutes once or twice a week.

Either of those will prevent 'varnish' from building up and save you the hassle of having to clean the carbs out every year or two.

Good luck.
FALCON