sync yer carbs!

[denydog]

Lay the smaller allen wrench in the bottom of the carb and screw in the idle adjuster until the allen wrench would just slide under the carb slide.
Adjust other carbs so small allen wrench would slide in, and next size allen wrench wouldn't.

Using a small diameter wire or other spacer to even up the throttle plates is often called bench sync'ing, since it's often done on the bench after carb disassembly/reassembly.  It gets you to a starting point, and will allow the engine to run, but is no substitute for proper air flow synchronization.  All sync'ing methods consist of adjusting the throttle plates, but measuring airflow is the accurate way, because there are other factors involved besides the throttle plates, plus the idle screw adjustments are very small, and at least on my bike, are interelated due to the linkage arrangement.  I.E., carb #2 and #4 are sync'ed to #3 and #1 is sync'ed to #2.  

[Fudge]

I just sync'd my FJ over the weekend also.  It's handy having my recently purchased throttle meister so I can lock the throttle at a steady RPM (3K for me) and balance the carbs.

[chornbe]

Sync'ing them on a Dyno with the engine in top gear, under load, running at cruising speed is the top-notch way to do it. Do the idle sync to get you in the ballpark, then cruising-speed sync to smooth it further.

[stk0308]

I keep meaning to buy carb sticks and do my Triumph.  I'd need to fab up some fuel line extensions though.  Darn FI bikes anyway    I have done it once myself and it did seem to make some difference in smoothness.

[Fudge]

Sync'ing them on a Dyno with the engine in top gear, under load, running at cruising speed is the top-notch way to do it. Do the idle sync to get you in the ballpark, then cruising-speed sync to smooth it further.

Note to self, buy dyno....

[chornbe]

Note to self, buy dyno....

Hey, sue me. I didn't say it was a PERFECT plan

[Walker]

I bought the same carb synch tool a few years ago.  It worked really well for the first while.  I kept in the box it came in and left the mercury in the little reservoir at the bottom of the gauge.  I guess, overtime, the mercury reacted with the plastic because when I got the tool out to use it a couple of months ago, the reservoir broke at the slightest bump and spilled my precious heavy metal all over the garage.    So I did what any self respecting grease monkey would do...I swept it out of my garage and down to the gutter so that the neighborhood dogs could lick it up.  

I think I'll try and fab up my own using the Motion Pro frame and some substance other than mercury.  Anybody have any ideas what to use?  

Oh yeah, back to 1K's original post...on my Seca, its amazing how much smoother the bike idles once the carbs are synched.  I can actually get 'em pretty close just going by the sound.  

The mercury contracted and expanded with temperature changes.  Add in the density, and the vapor pressure, and it cracked the plastic.  I had the same thing happen to mine, except I was able to extract the mercury before it spilled.  I used it and some parrafin wax to fill some custom hollowpoints for home defense (No lead poisoning for people trying to break into my house, I don't screw around!)

Anyway, anyone who wants to make a really cheap synch tool:  Get a yard stick, some zip ties, a wire coat hanger, and about 12 feet of clear plastic tubing.  Carefully staple the tubing to the face of the yard stick, running down one length of the stick and up the other length with a gentle U bend at the bottom (or use zip ties, whatever works and you have at hand).  Fill the tubing with ATF so you have about a 2 foot tall column of ATF on each side, use the wire hanger to create a hook, and 'viola!  You've now made yourself a very inexpensive and durable manometer.  Just hook up the tubes to the carbs you want to balance (1&2, 3&4, 1&4 OR 2&3), hang the manometer next to your bike, and levalize the oil column heights with it running.  Mine cost me nothing, I already had the tubing, yardstick, zipties, and ATF in my garage.  The only challenging part was getting the ATF into the tube.  The way I finally did it was to stick one end into the bottle of ATF and carefully suck on the other end.