I haven’t been feeling well and spent a day and a half in bed. I’m not taking calls today.
I’m tackling the backlog of work… Zephyr 750 valve clearance adjustment.
Very few people perform valve clearance adjustments. Nobody pays attention to them because of their surprisingly critical importance.
Even after adjustment, there’s no dramatic change, and valve noise doesn’t necessarily get louder.
But understanding not just valve clearance, but also the condition of the cam and the cam chain, is truly important.
Let me tell you why this owner decided to go ahead with the adjustment. After riding, an abnormal noise appears about 20 minutes after cooling down.
But there’s no noise from cold start through warm-up. Over a couple of days, I had the owner show me the noise.
It’s definitely an unusual sound I haven’t heard much before. Abnormal noises generally fall into two broad categories—rotational and reciprocating—and this one is hard to classify as either. If you’ve never inspected it, why not give it a check?
I opened it up right away. Since it’s air-cooled, it wasn’t too difficult to access. At first glance, nothing seemed wrong.
I started cranking to find top dead center. That’s when I noticed something unexpected: this engine doesn’t have an idler
(a device that forcibly holds down cam chain slack) between the cam chains. Instead, the chain slack is
held by a plastic damper attached to the head cover. And sure enough, the cam chain was sagging!
You can tell if there’s play in the cam chain by cranking, but with the head cover on, the damper wasn’t holding it properly, so the slack went undetected.
So I decided to adjust the cam chain in this state. It’s a semi-automatic type, so some adjustment is possible.
So we decided to adjust the cam chain in this state…it’s a semi-automatic type, so some adjustment is possible.
The adjustment range is in 0.05 mm increments. If finer shims existed, that would be ideal, but only the manufacturer has them,
so regular people are stuck with 0.05 mm increments. Two spots are too tight! They were 0.02 mm and 0.05 mm. Since I don’t have the right shims in stock, that’s all for today.
This is how valve clearance affects the cam, and checking the cam chain condition is a truly critical inspection.
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In this way, we can properly check how the condition of the tappets affects the cam and the condition of the cam chain—it’s extremely
It’s an important inspection.
