® common-motor.com sync video issues




YouTube channel Common Motor. Lot of videos. Some good stuff, some bad. This two-video series highlighting syncing a Honda CB550 is just strange. It is difficult to imagine a more crude and less accurate way of approaching this task.


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, the real weakness 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 consequential. But most of the things mentiined can be caused by other issues. And maybe these should have been mentioned.

The video made the single-gauge method sound superior.

Not even close. Have 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 78 CB550 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.

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.



For more powersports maintenance fallacies, see this article.

More book critiques: Julian Ryder, Mark Paris, Sean MacGregor


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