Is this a normal occurrence?

[thewormman]

1976 KZ900 Bit confused...
First time stripping one of these engines.

Took the head off due to valves sticking and two bent exhaust valves. 2 new valves, all valves ground in and head de-coked.
While the head was off and ready to go back on I put the cams back in on the bench, torqued them down and re-shimmed the valves to correct clearance.
Head back on cams back in, timing set up, everything torqued down. Started it up ran like a pig, so thought I'll go through it and make sure I set the cam timing ok.

While there I thought I'd check the valve clearances, FIVE of them all under tolerance, WHAT?

Is this something that happens with these engines??? I have been working on engines for 45 years and never came across something like that! Do the heads flex when torqued down or something?

[zed1015]

Newly ground or re-cut valves will always settle slightly and bed in once run which causes the clearances to close up.
Also some heads take on a slight twist when in their free state which straightens out once bolted down which can also affect bench set clearances.
It's good practice to check and re-shim the head after a rebuild or head overhaul.

[Gray17]

Yes thats exactly what i found too on mine, had the head re worked by engineering fiirm, all new guides and exhaust valve seats and valves,seats re cut, head skimmed etc the full enchilada, like you set clearences on the bench 1st without springs present. I had prev read that the clearence closes up once run so purposly left slightly wider gaps then the 15 thou. Didnt help though soon as id ran it for a hundred miles i re checked it, sure enough gaps had shrunk so re set again to correct clearences. It had prob done about 3 or 4 hundred miles and wasnt running right so fully stripped it for rebore, had this done re fitted everything expecting head still to be ok as not been touched, once again gaps had closed up so having to reset again? Im hoping any bedding in has now been done as its an absolute pain, much prefer the nut adjusting method then shims. Not just due to cost but also if you make a mistake you have to await a new shim before resolving.
Hopefully it will now run well