Hi Ains
It's interesting to read what you say about your bike running cool. My own SP4 runs cool also, and I was concerned that it may have been due to a faulty thermostat or temp. sender - in fact I even renewed the temp. guage a while ago, but to no effect! I only see the gauge rise above 55C when sitting for a while in heavy traffic - and it immediately drops again when I get moving. I've never seen the fan operate! Maybe I'll try blanking-off part of the rad. as you suggest - 'cause if the mixture's too rich then power will surely be down.
I guess the 'slightly too rich' mixture is the cause of all that lovely growling, and the occasional spit back through the cans though? (Hmm! It'd be a shame to lose that rorty sound track!)
My own bike won't tick-over when cold, but it'll do so quite nicely when warm. However, when cold-starting, it needs a good twist of the wrist and this leads to a strong smell of petrol from beneath the tank for the first few miles - which is a bit worrying! It has a completely open airbox too, so I guess that doesn't help. Is your bike 'smelly'?
Didn't know the top yoke plaque was silver - but it don't 'arf polish up with Solvol! I'll check it for a hallmark next ride.
Steve