1962 Superhawk Restoration: Here I go

[resurrection]

Maybe a loose wrist pin on the con rod.

Allowing some horizontal load ?

Or maybe The cyl a little tight or out of round.

[LOUD MOUSE]

Ya have a lot of SCUFF on those pistons.
And a lot of carbon for only that amount of miles.
How do the cylinders look.
Any aluminum there.
Probably would want to replace the rings.
Did the engine ever over heat? ............lm

Those pistons/rings have about 250-300 miles on 'em. Is it okay to reuse the rings since they're so young? They appear to be perfect to me.

HOW LONG YA RUN THOSE PISTONS/RINGS?

[teazer]

Scott, you are right that both valves should be shut at TDC on the firing stroke, but on the other TDC they should both be open slightly. 3mm sounds like a lot at TDC though. Are both valves open around TDC where the exhaust is closing and the intake opening?

Left to right should be the same but with a 180 degree crank, the cams are phased 90 degrees out left to right.

I'm looking at a pair of cams and a sprocket here on the desk.

The TDC marking on the right side of the sprocket is TDC on the right cylinder with both valves on overlap (slightly open). The left cylinder is at BDC and the exhaust valve is closed and the intake is fully open.

One revolution later, right cylinder is at TDC on the firing stroke and the left is at BDC with the exhaust valve almost fully open.

IS that what you are seeing?

Try to slip a large flat bladed screwdriver in though the tappet inspection holes and lever down on the tappet adjuster screw. Do all 4 open and close smoothly with no stickiness?

The noise is metal on metal and it's way louder than any CB72/77 I have heard running except the one that had valves and pistons getting intimate.

Something is hitting something.

[teazer]

Do you have a pic of the top of each piston? I'm interested in the valve pockets in particular

Is there any way that the valve clearances could have been excessive? It is possible to check them at the wrong place in the cycle and end up with too much clearance.

On the bench, try to rotate the camshafts and when one valve is fully open, check the other valve on that same cylinder. I can't remember the stock clearances, but they should be somewhere around .004" to .006" I would guess.

No way they were set to fractions of a mm and the conversion ended up a factor of ten out is there?

I know that's unlikely, but we are searching for something odd.

[teazer]

Is there any chance that the plugs are 3/4 reach? or of the side electrodes getting clipped by a valve? I have had both situations - silly I know but stuff happens.

[e3steve]

NAW.
I'LL JUST LET THE EXPERTS HAVE AT IT.

I, for one, would very much like you to share, Ed. As would many others, I'm sure!

I'D GUESS IF A EXHAUST PIPE HAD EVER BEEN RUN IT WILL NEVER HAVE OIL IN IT TO SMOKE.

Oil residue from storage/fabrication would burn off in minutes, surely(?), let alone miles. Oil in the exhaust header from the motor -- enough to cause exhaust smoke for, once again, more than minutes, would certainly be a lot of oil!? I have the feeling that you're 'testing' us here, me ol'mucker.!

Ya have a lot of SCUFF on those pistons.
And a lot of carbon for only that amount of miles.
How do the cylinders look.
Any aluminum there.
Probably would want to replace the rings.
Did the engine ever over heat? ............lm

I'm no mechanical expert but, IMHO, I'm in total agreement with Ed.

Carbon builds quickly when mineral oil combusts along with the induction charge. And the piston looks like it could've overheated and 'grabbed' in the bore; possibly too tight a rebore/honing tolerance? I don't see any blow-by, BTW.

As for the clacking noise Scott, did you listen around the top end with a stethoscope probe or a 'stethoscrewdriver' to closer pinpoint the source?

[LOUD MOUSE]

I just read this again!
The pistons are NOS third over. The cylinders were honed just enough to warrant slightly larger pistons. I was very, very careful about the cam chain's installation;

Did you not bore from .50 to .75 pistons?
Just hone to ???????. ........lm

The pistons are NOS third over. The cylinders were honed just enough to warrant slightly larger pistons. I was very, very careful about the cam chain's installation; redoing it a number of times to insure it was correct, knowing how much of a pain it would be to fix.

I noticed as I rotated the engine one full rotation the master link would be two links "off" each time until eventually returning to top dead center. I was informed this was normal, but that was only from one person.

There's always a possibility that it could have been a human error. Though my memory says it was perfect. Would one link really have that drastic of an effect? Is it possible the cam chain tensioner was loose enough for the chain to jump a link?

Just thinking out loud here. Thanks again for the feedback.

Scott, sorry to read about your accident. Riding two hours to O.R. with that damage. That's impressive. I dropped my wife's FZR400 the day I finished rebuilding it and complained for days about a few bruises. :-(

I am new around here but not to CB772's and I have to admit that I did not read all 35 pages of posts to see what you did inside that motor.

That noise is either a piston hitting the head or a valve smacking the piston. I had what sounds to me like the same noise in a motor with CB250 pistons. It was fine to turn over by hand, but fire it up and it made that noise. Motor out, head off, machine pistons slightly and sling it back together - 6 hours start to finish (with two arms).

It also sounds like a ton of tappet clearance, but that has been ruled out.

If pistons are originals or OEM replacements, I'd speculate that the cam timing is one tooth out.

Pop the top cover off and turn the motor over slowly and check cam timing first. While the top is off check the rockers to see if there is too much side play or anything else odd happening. With the motor on the bench and the top off, spin it over and see if you can locate the noise.

Pop the head off and look for shiny witness marks where things have been touching.

Teazer