Topic: My Compression test results - Good? (and new noise)

[mikethejeepguy]

Bike: 1976 CB550F

So after adjusting my valves and cam chain, I am getting a new noise from the top end. In my helmet, it almost sounds like a tinny hiss (technical terms). Listening to the motor from both sides, I suspect my valves. Either I'm being picky the more I ride, or it got louder after I adjusted the valves & oil change and it seems to get louder the hotter the bike gets. I know I adjusted them on the tight side, rather than loose. I suppose I should re-check them tomorrow.

Anyhow, I also did a compression test at operating temp and as per directions (open throttle & choke), using the starter. Here are the results:

No. 1: 150 psi
No. 2: 145 psi
No. 3: 140 psi
No. 4: 140 psi

I didn't do a wet test. Those numbers are ok right? Any suggestions on the valves? Been reading through posts. I guess the 550 is the same as 750, and looser is better?

Mike

[Johnny5]

I adjust my valves one thousandth over the manual's recommendation. The valves, when properly adjusted, do hiss sorta. Along with a light tapping sound.

[TwoTired]

Numbers are within 10 percent.  Certainly good enough for street use.

I adjust valves cold per the Honda shop Manual, always have.  I've got over 40K on one 550.  I don't think looser is better for the stock engine, unless you plan on winding up past red line a whole lot in hot weather...often.

Could that hiss be the sound of a chain sliding over a tensioner shoe?  Your cam chain tensioner has been adjusted and the lock nut re-tightened, yes? 
If your bike has high miles and/or had the tensioner over tightened frequently, the shoe material may be worn down and the chain rubbing on the metal backing.  That would be louder than if the chain were rubbing on the soft shoe.

Some of my 550s have can chain hiss more than others.  Oddly there is one with low miles that does this, and there another with higher miles that does not do this.  So, I bought a helmet that is better at keeping out that noise frequency.

Anyway, if you want an engine with no mechanical noise, you might appreciate one with a water jacket better.

[mikethejeepguy]

Thanks for the replies guys. The bike has 23,000 miles on it, so I guess it's about mid-life crisis time? Am going to re-check the valves, but that is a good point about the cam chain TT. Maybe after my attempt at adjusting it the other day has rendered it too tight. I don't know if you remember, but I was the one who's PO grossly overtightened the locknut and I had to grind it off. http://forums.sohc4.net/index.php?topic=51903.0 So I did the adjustment, rather I think the chain might have adjusted when I ground the nut off. I then did the adjustment with a new nut as per directions (15deg past tdc).

I suspect I might have some issues with the tensioner. I am now wondering if there was a reason the PO tightened the heck out of the lock nut? I'll re-check that as well.

A water cooled bike is not an option I'm afraid I LOVE my 550. Maybe a better helmet.. You do have a point there. I wonder if I'm being a bit picky about the noise. I'm a horrible perfectionist. But you are right, my experience, though limited, is generally with newer, water cooled bikes (03 CBR600 F4i). This being my first CB, maybe much like my Jeep Wrangler, notorious for various "Jeep clunks", there are inherent CB noises. Anywhere from 1500 or cruising at 4000, this one sounds like a combination of a mechanical hiss, maybe a light ringing once in a while (like a key ringing on the bars?), and a light tapping. If I didn't hear it coming from the top of the motor, I would suspect my speedo/tach cables. That kind of noise. I know this is like doing brain surgery over a fax machine. Maybe I will shoot some video of the noise.

This might be a dumb question, but is there a way to back off the cam chain tension if it is too tight?

[TwoTired]

The 550 cam chain tensioner is "automatic" once you release the lock nut, by design.  An internal spring forces a shoe clad metal arch to flex into the slackened cam chain (15 deg).  The stud and nut freezes the arched shoe to hold its position against chain centrifugal force, without further need for the internal spring (until the next adjustment cycle).

When you release the lock nut, you can use the screw slot to verify the adjuster is free to move (and feel the internal spring tension).  The internal spring should do the rest, let it, and then lock down the stud.

There is a alternate method discussed in previous posts, of actually putting pressure on the screw slot while the bike is idling, to reduce chain noise.  However, too much pressure just wears out the slider shoe faster.  And, there is a risk that the abhorrent cam chain noise will just return is a couple weeks as the shoe wears.

Your cam noise may vary....