Just bought a compression test gauge and checked the compression on my bike. I just got the bike back together after changing out the head gasket.

The compression read from left to right...

150/138/140/150 (psi)

The motor has about 46000 miles on it.

I only removed one plug at a time for the testing.

I have not been able to ride it yet because there is a tapping/knocking coming from the valve cover when it's running that gets louderas you throttle it up.

There is NO smoke or obvious signs of missing while running.

Do these compression numbers sound bad. The Clymer Manual calls the spec to be 185 psi+/- 28 psi.

 

They are all fairly close, and I'd say that 138 ought to be enough to run on, although it isnt ideal compression, so you're not making the absolute best power you could. the middle cylinders may have a leaky valve seat, or something of that nature causing the slightly lower compression numbers. but 46k miles isnt brand new either, so its just regular wear/tear.

a tapping or knocking? does this sound change with engine speed? or no? it could be any number of things, but my money is on a cam bearing going bad on you, or maybe a valve that is seriously out of whack.

 

Quote "a tapping or knocking? does this sound change with engine speed? or no?"

Yes. It gets louder. It almost sounds like something is hitting something. It wasn't there before I blew the head gasket. It's about like the CCT noise when it's at it's worst.

The head gasket blew onone of the inside cylinders (#2 or #4 firing order). Can't remember for sureright nowwhich one but it was close to the inside.

I did peg the temp gauge bad when it blew. Supprised I didn't loose the whole bottom end.

The cam bearing going bad? That would mean changing out the head and or the brackets that hold the cams in. Right?

 

if the cam bearings are going, you have to replace the whole cylinder head, cam caps included.

did you by chance get the head machined before reinstalling? that would account for the discrepancy in compression if you didnt.

 

I didn't get the head machined. I checked to make sure it was not warped. It was in spec so didn't want to spend the extra money not knowing if I did more damage to the motor from over heating it.

When I'm just turning the motor over, I don't hear the tapping noise. I only hear it when it's running and when the valve cover is on.

I've got the valve cover off right now, have started it several times and can not hear the noise.

I'm going to check the valve clearance. Maybe I can find something there.

 

can you perhaps post a video of the sound and its location? that would help greatly.

 

I dont have a video camera and I can't tell where its coming from. I may could use my phone to get a short clip but not sure of how the quality will be.

Its not very noticeable with the valve cover off. Once I check the valve clearance I will reinstall everything and try to get a clip of the noise while its running. It sounds a lot like the CCT but tightened it up and it did not go away.

I will double check the torque on all the cam caps. Maybe I missed one.

Im going to have to wait for the motor to cool back off before I get back out there. I kept running it for short periods of time trying to track down the noise. I have an oil mess to clean up now.

I even tried using a cheap automotive stethoscope. I placed the rod straight onto the cam caps and could not tell any difference between any of them.

One thing I did notice was I didnt tighten the center screw that holds the breather base on but I cant imagineit making that much noise.

 

my money is on a cam bearing being toast. pull the caps, and if they're anything but mirror finish shiny, you've got a bearing problem.

 

Im looking at a new head and cap assembly right now and their running about $1000. I paid $1200 for the bike about 3-4 months ago and now have already sunk several hundred more into it. If I buy a used motor Im taking a chance of it being bad too. Know of a cheap place to order a head and caps?

Im going to try adjusting the valve clearance and hope thats all it is. After I get it back together and the sound is still there, I can get a recording ofit then.

Somebody who is good at welding aluminum could make a killing at repairing these head and cap assemblies.

Will check the caps while I have the cover off.

 

I agree with everything Hurricane Rider has said.

In case it helps: regarding the compression pressures themselves, they may be better than you think because:
1. Compressions should be measured with all the plugs out - it looks to me like you took them out one at a time.
2. The adaptor you screw into the head can make a big difference to the reading, if it leaves some dead space that the genuine Honda compression tester doesn't. The adaptor I use drops the measured pressure by about 10%.

Hope you get the tapping noise sorted. My experience with these engines is that even a small excesss of valve clearance (like 1/4 turn out) causes a lot of extra noise, but it should be more obvious when the cover is off.

The cam caps can be tricky- someone broke the cap on one engine I have by tightening the hold-down bolts out of sequence. Will keep monitoring your posts in case you draw a blank on the cap wear.