Topic: Is it possible to sync cb500 carbs with 2 clocks.

[Korven]

I've seen on more modern bikes that you can sync each pair first then the pairs with each other. is this possible or a waste of time?

[goodtryer]

Synch master carb with gauge1.
Make note of the reading.
Disconnect gauge1.
Connect gauge 2 to the SAME CARB.
Ensure you get the same reading.
If the reading is different, adjust the GAUGE to match - not the carb.
Now you know the gauges are measuring the same.
Leave gauge2 in place on the master carb.
Connect gauge1 to each of the remaining carbs one at a time and adjust the carbs to match the vacuum on gauge2.

[seanbarney41]

I doubt it will work.  Adjusting one carb changes the reading on all other carbs in strange and unpredictable ways on these.  This will be an exercise in tail chasing resulting in worse sync than mechanically insuring all slides are at the same height.

[TwoTired]

Each adjustment changes the engine RPM.  Each RPM change also changes the vacuum reading, including on the master carb.  What is the vacuum reading on the carb not attached to a vacuum gauge?

Anyway, the only hope would be to keep one gauge on the master carb, and sync each of the others to it, in turn.

But sometimes, having a cross point screwdriver AND a straight slot screwdriver is better then using the straight slot screwdriver in the cross point screw.   It's a best tool for the job thing.

Cheers,

[flatlander]

it sounds like it would be more hassle than worth it. usually you need to vacuum sync these once and then never again. maybe just go to a friendly shop that can let you use their gauges?

[brianc]

I have One gauge. I made a manifold with taps so that I turn on and off each cylinder as I go through the sync. All cylinders go into the taps / manifold with the gauge at the top. It also has a tap which is adjusted to damp out the fluctuations.
I use this on my 4 cylinder bikes and my CBX 6. The problem of gauge calibration is gone. You just have to keep tabs on which taps are open!!!!
I'll post a pic when I take one.

[bryanj]

Yamaha did a single gauge with a rotary valve/switch to connect to each port, it was a real pia to use so sat in a workshop corner gathering spiders.
When you adjust any one the others move as well so a decent set is best.

[PeWe]

If bench sync is not enough. Morgan carbtune easy to read all carbs and compare them side by side.
https://www.carbtune.com/

[goodtryer]

So “don’t even try it” or “buy new equipment” or “do a mechanical method” that everyone says is only enough to get started with before doing it the right way...

I wonder if there’s any compromise method that makes use of what the OP has and is better than doing nothing at all even if it’s not good enough for a factory works race team?

[seanbarney41]

Guys, most race carbs don't even have vacuum ports, so you bench sync and away you go.  Sync only affects idle, so if you can can stand a lumpy idle, no need to get in a fluster over a $100 dollar tool that you will probably use wrong or break anyway.

[bryanj]

Unfortunately this is one of the few jobs you need the right kit to do properly!!!!!!

[Korven]

Looked at ebay on kits like these; https://www.ebay.com/itm/Fuel-Carburetor-Synchronizer-Carb-Vacuum-Gauge-Sync-GS-CB-KZ-XS-550-650-750-850/283237753755?epid=24025355235&hash=item41f249239b:g:iscAAOSwknJXw-qg

But turns out the kit that Pewe linked is at the same price, i thought it would be alot more expensive. Does it have everything i need or do i need to get longer adapters to use on the cb500?

Offtopic: saw this: "For most bikes with fuel injection, you still have to balance your throttles. Carbtune II will do this as easily as it does for bikes with carburettors" Might explain why my vfr800fi is a bit rough idling going up and down 200rpm while cold.

[flatlander]

the morgan carbtune has all you need in the kit, and is easier to use than the clock type gauges.
you can add longer adapters if you want, but they are not necessary.

[BenelliSEI]

......... back to the original question: I’ve tried it, don’t waste your time. Get (or borrow) the correct equipment. Life’s too short.

[Tracksnblades1]

If bench sync is not enough. Morgan carbtune easy to read all carbs and compare them side by side.
https://www.carbtune.com/

Does the included adapters fit the old keihins...?
 

[Korven]

Did anyone try the https://www.carbtune.com/colortune.html that is also offered on the site pewe mentioned?

[bryanj]

The ONLY way is a DECENT set of 4 gauges, been working on these since the 70's and tried everything else and it dont work!

[evinrude7]

+1 for the morgan carb tune.  super easy to use.  excellent results. 

[PeWe]

I have only used my Morgan carbtune on Mikuni TMR32. I had to add a thinner hose (clear) to fit the small spigots on the carbs.
Easy to adapt for the spigot used.