Hello,
Question, I am rebuilding the cylinder heads on my 1981 V1000 G5 and require some info regarding Valve clearances. According to the Book 0.008” inlet and exhaust, guzziology says inlet 0.006 exh. 0.008 and I have in the past had other answers of various gaps.
The reason I ask is that the rebuild was caused by Exhaust valve problems, possibly caused by poor Supermarket fuel. Definitive answer would be appreciated.
Thanks,
Ian.
Just to confuse things even further, I was advised to set inlet to 0.008" and exhaust to 0.009" 
Always did it that way, no problems (but it might be a bit ‘rattly’).
I’m disinclined to believe that supermarket fuel is much different to anything else we might buy, and I run all our family’s vehicles on Tesco’s offerings as it’s convenient. No issues so far.
Turning to valve clearances, I’d be inclined to follow Mike’s advice, I can’t recall where I read it but “a rattly Guzzi is a happy Guzzi”. Obviously, there’s a limit, you can have too much of a good thing.
I had a look on the raceco site some years back and they suggested 10 and 15 thou fir a noisier but much more responsive Moto Guzzi.
I can’t understand why increased clearances (which must reduce valve travel) should improve performance.
It should make the valve duration shorter - but too much and the pushrods might jump off! 
Mike, I agree on both counts!
Same question though, if you reduce valve lift, and valve opening duration, how does this improve performance?
I might imagine increased turbulence, which could, possibly enhance the burn, but the cylinder fill must be less, which must limit the power.
I suppose that would lead to a reduced power peak, which might translate to “more flexible”, but I think it means “flatter performance throughout”.
No, I don’t get it either! 
I had a look for the raceco site, where I originally found this info. it seems they no longer operate. Sure I wrote it down somewhere, so I’ll have a look for it.
Would certainly be interesting to understand what they were getting at.
Never yet had a “bum steer” from Guzziology
Ha, I was wrong! I knew I’d written the info down somewhere. Inlet-8thou; Exhaust 10thou. Better tickover and low rev response, according to Raceco.
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8 & 10 sounds entirely reasonable.
In principle, the smaller the better from a performance pov, but not so small that the clearances become negative at any point in the engine warming or cooling cycle and allow blow-by, which will rapidly lead to erosion and loss of compression.
Or indeed so negative that valves and pistons kiss…