Topic: Noisy head after lapping valves. Normal??

[Soos]

A '79cb650 with 750(stock) pistons, new rings, and home-done head job.

I know i should re-check the valve clearances either now or soon...

But As it sits, my motor has 20 miles on it, and the head noise is seriously too much.?(I think)


From the first second the motor fired after re-assemble there is a distinct.... slapping? noise from the head.
I know (or at least pray i was right) it's not valve to piston interference.
I had used some clay to find the valve to piston clearances before final assembly.
It had just under 2mm clearance.
mabey 1 1/2 at a minimum.
Kinda hard to measure clay.

But anyways.... the head, i lapped all the valves, and being cheap/poor... no just cheap at the moment...(for now) I did it myself.

The intakes took very little to get a clean seat...
The exhausts though...... thats another story. I tried to keep all them close in seat sealing area, but even then, they are pretty wide seats IMO, could this be my slapping sound?


I did check my timing,(twice now), tensioned the cam chain, double checked the carbs are synch'd, did a valve clearance adjustment only once so far, running straight 30 weight oil(new pistons and rings)


l8r

[kayaker43]

lapping the valves shouldn't cause a noise. Most likely the cam chain adjustment is off, like the crank wasn't positioned right when you did it?? Its possible too that the crank might have moved while adjusting the valves resulting in too much clearance.

I"m betting its one of those two things and they are easy enough to check. Otherwise your cam timing might be off? If you check the valves again and find one with huge clearance, look at the adjuster screw. If you have to screw it way down to get the clearance right, you probably bent a valve and its not closing.

Did you leave out an exhaust gasket, a leak there can make a fairly loud ticking noise? Just throwing ideas out there....

I know your on a budget but I hope you honed the cyls before putting new rings in,.. won't cause a noise, but won't seal either.

[Soos]

The cylinders were bored out from 59.8mm to 61mm, and they were professionally done.
I know the exhaust gaskets are there, and sealing.
I took an incense stick, and watched the smoke for any telltale leak spots near the exhaust collars. Didn't find any.

I'm thinking i might need to re-check the valve adjustment...
It seems odd that the sound seems to come from all 4 cylinders as far as I can tell.
It doesn't seem to be isolated to one side of the motor or the other.

I'm not complaining of power... it seems to want to GO....

The highest RPM i have allowed myself to go to (so far) is 5,000 rpm.
it seems to go away with any RPM's above about 3,500 rpm.
At 5,000 it seems quite normal sounding.(comparing it to the stocker motor sounds I remember)

cam chain adjustment?
You are meaning when I installed the cam?
Or the tensioner?
If by the timing of the cam... I HOPE NOT... But i might have to check if all else fails to cure this noise before too long.(hate to kill this motor before i get to actually let it breathe WOT...

The tensioner i tightened by the book. twice. no change the second time i checked that.


It almost sounds like a sewing machine.... a really old one.

I checked for oil, thinking I might have killed a cam or something, nope, plenty of oil up top.



l8r