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How to measure the valve clearances on head with head off.

ukjules

ukjules

Forum Sage
Having been through a head rebuild i wandered if there is a way to measure the valve
clearances with the head on the bench ?
> This would have saved me an enormous amount of time and stress.
> The engineering company informed me after I new this would have been useful , that they always do this
on engine rebuilds.

i.e. valves in, and lapped, springs and collets in , buckets and cams in and tightened down.


BUT:

How do you turn the cams to check the clearances ?

I just wandered if anyone does this as there are many reasons why this is very very useful.
 
its a bit time consuming but you set the cams as described in the manual and torque them down. check the relevant shims and replace as nessecary, each time you have to change a shim or move the cams to a different position you have to unbolt them move them round and retorque them down again
 
We just do the shims with no springs in on a test fitting. (Our just put the inner springs in) Just Valve bucket and shim and cams bolted in. Just do a valve at a time and hold the valve in by hand and measure what shim you need. It works out dam close of what you need when fully assembled. Any rebuild is time consuming. Its all in the detail.
 
thanks both,
Many thanks that is a good idea. I obviously can do it on the bike but that method on the bench
would have saved me time and stress as an inital overview. Not exact as you say but will be enough to identify issues like i had
and you can at that point further investigate.

It is at that point on the bench you want to know if your valve does or does not need grinding down a bit.
I ended up fortunately finding a chap with a shim grinding tool. I am out of Suzuki spec
but the bike is at least perfectly tuned re the valves. It runs like a dream now.
I took the shim down to 1.90 (yes out of spec and a risk) but I have been 60 miles and no issues.
the shims are hard all the way through.

I have another head I am going to rebuild for backup or to sell and will use the bench method this time initially.
thanks for info - i could not think how to do it !
need to take a braek from mechanics and go for a long ride.
 
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I just did this on my KZ engine.

As mentioned, assemble one valve at a time using only the inner valve spring. I did not bolt the cam in place, rather I just layed it in the bearing saddles and pointed the lob away from the bucket. Measure clearance and select shim. Target the shim selection to provide valve clearance at the top of the spec range. With the head fully assembled the clearance will be slightly less.

EDIT: made a mistake here. The clearance will be greater with the engine assembled. Not a whole lot though.
 
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I did this on my 1000G. Really easy with the springs out, but I had to do it again with the springs in (long story). The heads of the screws that hold the cam sprockets on provide a place for a flat screwdriver to get leverage against the shaft of the cam. Use that to turn the cam.

With all the springs installed and the cams in snug, you'll get the same clearance you would if the head was installed. And it's still easier than when the head is installed.
 
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All good info this. I so wish i did it before i put my head back on.
I just didn't think - but people doing head rebuilds should take note of all this.
Fortunate to have a second head which i will rebuild and will def do this.
 
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