Sync-ing Carbs

[wvcajun]

What is the best, cheapest, most reliable, easiest to use carb synchronizing tool to use? I am sure there is not one that fits all those criteria, but what does everyone think?

Thanks,
Matthew

[lorazepam]

the cheapest tool is the mercury filled "carb stix". they use tubes that pull the mercury up into with the vacuum generated by the carbs. For precision, and ease of storage and use, the Twinmax is better, but more expensive. I have used the carb stix for years and have had no problems with getting things right. they can be purchased online from most motorcycle parts and accessories sites. I got my last one from ironpony.com.

[R75_7]

On the Air Head Beemer web site there's a thread about a home made carb sync tool. I believe it is made for about $4.00 and is supposed to be very accurate. I've never tried it due to not having a garage to work on my bike. The method reads very sound.

[kbasa]

I bought a pair of carb stix for $20 at a flea market.

Even came with the mercury and the little restrictors you need to keep the mercury from getting sucked into the motor.

I aspire to a TwinMax, but they're $70. I instantly translate that into 90% of a tire.

:dunno

[Braddog]

JC Whitney also sells the necessary tool. I think they sell a couple different models, I think they have one for $59.95 that will do everything you need, including 4 cylinders.

[The_Veg]

There's a current thread over at boxerworks.com about the $4 tool and it gets universally good reviews from those guys.
One of them suggests going a tad further: Once the carbs are synced, try turning the screws in and out by 1/2 turn or so, one at a time and always returning to the starting point, and while doing so LISTEN to the engine. it will tell you enough to get a very good state of balance without a visual indicator. YMMV of course, and I have not tried this or any method as yet.

[flash412]

Here's how you sync carbs with no special tools at all...

If you don't have a throttle stop screw, you'll need a friend to help you set the running sync (cable balance). Do this BEFORE you set the idle sync. Rev the bike up to the rpm where you find you ride the most often... 4000 5000, where ever the "sweet spot" is for you. LOCK the throttle there. Now take the throttle cables on each side, a few inches above the carburetor and bend them slightly one at a time by pushing your thumb against the cable, pushing it between your middle and forefingers. Just bend it a little. If ONE side causes the engine to speed up and the other doesn't, then they're out of sync. Loosen ONE lock nut (using the 10mm open end wrench from the toolkit), either one. Adjust the adjuster in or out as appropriate. Give it another "bend test." Repeat until bending either cable causes a slight increase in RPM. Tighten locknut and retest.

Once the cable balance is done, setting the off-idle sync is also simple and also requires no tools (other than a flat blade screwdriver). This must be done AFTER the cable balance sync is completed. With the motor off (and preferably cold), have a friend help you. You bend over the bike and put both a finger on each idle adjust screw. (I find this easiest to do coming up from below the carbs with the palms of my hands on the bowls.) Have the friend twist the throttle SLOWLY. You can FEEL which carb comes off idle first. Adjust one idle adjust screw in or the other out and repeat until they're even. Any unbalance when it is running can be taken out by the mixture screws. (You CAN do this by yourself if you stand on the left side of the bike with your finger on the LEFT carb while you have your right hand on the throttle and LOOK at the right carb.)

You have now adjusted the two places where you have control, off-idle and cable sync in the sweet spot. They're carburetors, run by cables. You CAN'T get them any closer than this even if you have $10k worth of diagnostic tools. They WON'T be synced everywhere in the RPM range no matter what you do. If you use this method, you will be VERY happy. Yes, I have carb sticks, lost somewhere in the bowels of my garage. I never used them after trying them once. This method is that much better.