Re: Bike won't rev properly..

Posted by LukeM on Mar 13, 2012; 12:17am
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/Bike-won-t-rev-properly-tp3812078p3820926.html

Unless I miss my guess, that is a fuel manifold valve.  It sits between the outlet of the petcock and the input for the fuel rail for the carbs.  There is a third line that should go to a vacuum source (possibly near carb #2).  The idea is that when the engine is running, fuel flows to the carbs, and when the engine stops (no vacuum) fuel stops.  This allows you to leave the petcock in the ON position all the time.

You _can_ bypass it, but you you'll need to switch the petcock off when the bike sits to keep the carbs from overflowing.  I had one on my bike, and it was only a problem if the bike wasn't run for 3-4 days. If it's ridden daily, it's not too annoying.

You might also want to put an in-line fuel filter between the petcock and the valve (or the input to the fuel rail, if you bypass the valve) to keep dirt out of the carbs.

So, is it running any better?
Luke M