Good source for Vacuum Gauges to synch carbs?

[Egaeus]

Does anyone have a good source for the vacuum gauges needed to synch the carbs?  My bike is running on one cylinder when cold, and I've done everything I can think of but a valve adjustment and a carb synch.  We played with the synchronization screw, and it seemed to affect it, so I figure that's the problem.  However, I can't seem to find the set of gauges for balancing them.  There are craploads of single gauges everywhere, but you can't calibrate them with each other.  Any good online sources or suggestions on where to look locally?

[Mandres]

Hey Robert, check this out:

http://gstwins.com/gsboard/index.php?topic=3521.0

[GeeP]

Take about an 10' length of 1/4" clear tubing.  Tape it to a yardstick in a "U" shape.  Fill the "U" halfway up with water.

Attach one end of the hose to one vacuum cap, and the other end of the hose to the other vacuum cap.

Start the engine and adjust the balance screw until the columns level.  This is important becase of the sensitivity of the meter.  It's easy to suck the water out of the tube!  Vacuum differential increases as engine RPM increases.

Now run it up to the required RPM as stated in the service manual.  Fiddle with the screw very gently.  When the columns align, you're balanced.  It's FAR more accurate than a mercury gauge, and at less than $5 you can't beat it.

You're not actually measuring the absolute vacuum like a Mercury gauge.  Instead, you're measuring the differential between the two carbs.  Since a 1" column of Mercury is equivalent to a 13.6" column of water, it's 13.6 times as accurate than using a Mercury manometer that costs 10x more.  

This is part of the reason why I love the little twin.  Simple and easy to work on.  

Edit:  Yeah, that's it!  Far fancier than mine though!   

[Egaeus]

Mandres, that is GENIUS!  *I* should have thought of that!  

Seriously though, I have a primitive barometer sitting in my living room that works on the same principle.  I don't know why I didn't think of doing that.  I'll just blame it on being an *electrical* engineer....

Thanks for the link.

[Egaeus]

Edit:  Yeah, that's it!  Far fancier than mine though!   

It is a great idea though.  The great thing about the one in the picture is that it has the valve, which when open will keep them level, and as you close it, it will begin to have a differential in pressure, helping you keep from sucking water into a carb.  I love it!

[Blueknyt]

Ya only need one guage really, i built one i seen on another site.

looking......

looking......

Ah, here it is. http://www.xs11.com/forum/showthread.php?threadid=986

only diff is mine has one end threaded to put everything inside. ill get a pic of it in action on the katana Friday.

[Egaeus]

So I built this differential manometer today.  I paid a bit more than $5 since I couldn't get air line at the right length, so I had to buy 25'.  It was about $7.50 total.  Anyway, I'm very glad I persisted in finding a valve, because they were so out of synch, it would have sucked the whole tube of water down the carb if I didn't.  It was bad....

Anyway, it's almost all sorted out now.  I was actually able to ride it in the parking lot for the first time in the 16 days that I've owned it.  Now I just need a chain and some tags and I'll be set to take it out on the road!

[Mandres]

where did you go to find the parts?  Would someplace like Wal-Mart have the needle valve? 

[Egaeus]

I got everything at Petco.  They had a $2.49 bag of various plastic parts including the T's and the valve.  The 25' of airline was $4.99.