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Re: Bike won't rev properly..

Posted by seestheday on Mar 13, 2012; 4:18am
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/Bike-won-t-rev-properly-tp3812078p3821283.html

Sorry, I probably wasn't being clear. I meant to try bypassing it as a way to troubleshoot if it was the problem. Removing it completely has other implications as you state.

For what its worth, mine failed (rubber inside disintegrated), so I just removed it.
Sent from my BlackBerry device on the Rogers Wireless Network

From: "LukeM [via Honda CB750'S]" <[hidden email]>
Date: Mon, 12 Mar 2012 17:17:01 -0700 (PDT)
To: seestheday<[hidden email]>
Subject: Re: Bike won't rev properly..

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
Back on 2 wheels after a 30+ year break. Used to have a 1979 CB750L, sold it as a parts bike, now riding a 1984 VT700C. Central OH, USA, Earth, Sol System, Milky Way Galaxy, Universe.



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NAML
1981 CB750K with 900 cams
90K KM's, rebuilt head, rebuilt carbs, upgraded valve stem seals

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