Total Motorcycle Community Forums

koconno2 wrote:I hope someone is still answering this string. This seems like great information for old bike owners like my self. I have a 81 Honda CX650 with two carbs. I have very little experience with motorcycles and since I have the engine removed from the bike for an alternator R&R I thought I should tune the carbs after the reassembly.

What causes the carbs to become out-of-balance to start with? Are there worn out parts that should be replaced first?

Screws can be vibrated out of their positions, for one thing. Metal can warp, as well.

koconno2 wrote:Are both ends of the manometer attached to the carbs?

Yes. Each carb gets one end attached to it. This way you can tell which carb's throttle is open more than the other.

koconno2 wrote:Do you attach the manometer to manifold vacuum or venturi vacuum?

Each carb, or carb intake, should have a nipple or port to hook the gauge in to. Manifold vacuum only measures the total vacuum, it doesn't compare one carb to the other.

koconno2 wrote:Could I use vacuum gages instead of a manometer?

Yes you can, if and only if you have shown they are calibrated perfectly. Absolutely laboratory perfect. Otherwise it's going to be worthelss. Dropping the $5 on some ATF and tubing is a much better, more accurate solution.

Great, thanx for the info.

Great idea my Syncro is too bulky to carry and mercury almost impossible to find. Wish I had CV or slider carbs on my 91 They never stay in sync.

also matey;

A harley guy that says who needs a chain bet you Always ride on macadam Wait till you get a rock in your belt, unless you got an XA then you know that Der shaft ist mightier dan der chain.YA

I've used this method and ATF for years with great success and actually prefer it over the "proper' gauges which I have.

On some bikes, like my CB750 I remove the tank altogether and place it on a step ladder near the bike and just run hoses to the carbs. Some bikes, like my 05 Ural nothing has to be removed, just put the petcock on prime, plug the tubes into the vacuukm ports and she's good to go. Some bikes you can remove the tank and there's (barely) enough fuel in the system to sync the carbs without doing anything.

Did the manometer described above but used 10-w30 oil , it was a little slow to move but it did the job anyway.

If you look here you'll see another type of manometer made out of two baby bottles.

This is awesome. I have a proper set of the cheap (no restrictors)carb balancers from Motion Pro, but they used mercury. The problem has been that each time I snap the throttles, th e bike sucks a bit of mercury in. Now there isn't enough left in there to do a proper job . I was wondering what to do, now I know. I'll just reomove the rest of the Mercury and fill it with ATF. Thanks!

Peter, you'll need much longer tubes, almost twice as long.

I know this is an old thread, but I wanted to throw my hat in the ring and let folks know that The Digi Sync is definitely a Carb (or Throttle Body) Sync Tool they should be considering.

There are a variety of options out there for Throttle Synchronization. I'll quickly give you a run-down:
1.) Ignore it and live with the loss of performance and gas mileage.
2.) Tune it by using only the sound your ears hear. The only mechanics I know that can pull this off successfully have +20 years of experience.
3.) Mechanical Dial/Needle Gauges. These require troublesome calibration, and the needles bounce all over the place, leaving you wondering just how accurate your Synchronization really is.
4.) Manometer Fluid gauges. These fluids evaporate and need to be replaced from time to time. Plus, there's the risk you rev your engine too high and suck the fluids in, causing engine damage!
5.) Professional Digital Carb Sync Tools. These are the easiest to use because they automatically calibrate and give you trustable accuracy that exceeds your manufacturer's specs. However, these come with a "Pro" price tag ranging from $500-$2,000!

Wouldn't it be great if you could get a Professional Digital Tool for this task without spending a ton more than the Mechanical or Fluid gauges?
We're not business people. We're just engineers who also love wrenching on our own bikes. We, like you, want the best tools, without paying outrageous prices. So, we created this tool for ourselves and shared it with our friends at local bike meetups. That was in 2015, and the response was so amazing that we decided to spend the next 8 years perfecting this thing into what it is today.

The Digi Sync is quickly becoming "the tool" that motorcycle repair shops love and trust for Throttle Synchronization.
Need more proof? The Bearded Mechanic (215K YouTube Subscribers) says that after he got his Digi Sync, his old needle gauges became "Wall art".
We've worked hard to get our starting price down to just $145.95 so that this isn't a Mechanic's only tool. It's intended to be a tool any DIYer can use. If you can figure out how to change your own oil, you can do a Throttle Sync job. We've had many customers tell us that The Digi Sync made the task so easy they were done in 15 minutes!

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