® common-motor.com sync video issues

YouTube channel Common-Motor Collective. A great channel in terms of what they succeed in doing is largely to educate. This two-video series highlighting syncing a Honda CB550 is not at all representative of the good information and mostly good parts on the website. In fact, this will be short because there aren't that many mistakes. That said, this video is strange. It is difficult to imagine a more crude and less accurate way of approaching the task of carburetor synchronization.

One gauge, eh? Any experienced mechanic would know intuitively the problems with this.

This isn't the first time someone tried to sync multiple carburetors using only one instrument. Jim Bowman created a special gauge with water cooler valves embedded in a machined aluminum block. This was in the early 1970s. A unique idea, and at face value an enterprising concept. But a single-gauge setup proved to not work back then and it won't work today. Two reasons. First, a single gauge provides no comparison of one cylinder to another in real time. Second, a huge drawback is the lack of tracking option when you change connections from one cylinder to another.

This video makes almost everything that could possibly be wrong with a bike sound like it's due to carb sync.

Sync is very critical. But most of the things mentioned can be caused by other issues. And maybe these should have been addressed instead.

The video made the single-gauge method sound superior.

Not even close. Having multiple gauges is just the beginning of good practice.

"Zeroing" the gauge?

This is ridiculous. Gauge-to-gauge calibration is done with the bike idling, where the gauges will be used, after all. That is what the gauge calibration screws are for.

What? 2000-2500 rpm syncing?

The whole point of syncing at idle is for...idle. There is no benefit in doing it anywhere else. The 1978 CB550, with its more advanced carbs, is better in this regard than most. But no Honda multicylinder maintains sync as the throttles are opened.

There are way too many steps in the sync process.

I think folks will be, beyond misinformed, actually disillusioned, by this tutorial.

The mechanic is never shown blipping the throttle.

A significant oversight. Sync won't be accurate otherwise.

The video never mentions pilot screw adjustment.

The two are done together. Pilot screw adjustment affects sync. And on another level, very bad sync makes pilot screw adjustment invalid.

The mechanic held the choke knob up while starting.

This means the choke cable needs adjusting or is broken.

There's more...

There is more, but the point is not to insult or defame. Common Motor has the right idea in making these videos. I applaud their effort and motivation. I just wish expertise was more consistently demonstrated in them. The inexperienced watcher of this video should not view this video as portraying best practice.

For more powersports maintenance fallacies, see this article

More book/video critiques:
Julian Ryder
Mark Paris
Sean MacGregor
Randall Washington
Common-Motor Collective 450 engine rebuild

Last updated February 2023
Email me
© 1996-2023 Mike Nixon