When I’m riding it the engine feels great, revs nice and freely and pulls well but just seems to rev out at about 50/60 tops. It certainly feels like a gearing problem to me ...
When you say rev out, is she fair howling? you want to take pity on the motor, she cant give any more... I'm more familiar with the larger motors although have ridden a mates star twin and that is a real smoothie, purrs along at the speeds you mention effortlessly all day without showing a sweat. When I had a super rocket in road trim that was happy at 60/70mph open road cruising and not revved out but was on song with more at hand for passing. For road use these bikes are not naturally tapped out as we want to get home, they do like revs and eddie dow once quoted the safe continuous red line at 6800.
I certainly am not a fan of over gearing, you put more loads through the engine and reduce the oil pressure. Once they are warmed up they are happy to buzz along all day. It doesnt do them any harm and the hotter cams like more than 4000 on the clock and sing at six.
There are many reasons this engine could be a bit constipated, tightness, too big a carb or incorrect jetting, too restrictive mufflers. But
not I would expect gearing.
I would expect you would need to be on sidecar gearing to rev out at 60mph or be on a c11 (they do run out of steam at 50!).
My zb33 absolutely barks (the exhaust note hardens up) at speeds over 60mph but its practically still only doing around 4000 odd (guess) as can be wound out to close to 80mph at which point she has gone flat powerwise (being around 5000) being on cooking cams.
But if you think its buzzing too hard and has nothing left, try amending the gearing by all means, its easy to do. Might though be worth doing some maths on what your current 60mph is in RPM. Its easy enough to do. You should be able to do that speed in third.
