You are correct, Adam, but the principle of changing down to avoid labouring in any gear will increase the cooling of any fan cooled engine.Adam_Winstone wrote: ↑Tue Dec 10, 2019 1:54 pmAnother quick question, which I may already have missed comment on... I don't suppose that you're running an advance/retard ignition are you? I ask as this could also explain why the bike is running hot at running in revs in 4th but cools when you down-change and/or 'give it some (an advance/retard ignition would then retard further and run cooler).
Just a thought.
However, a retarding ignition should enhance that even further.
My belief is that a good ignition set-up with advance/retard function can be made to work well if the curves are suitable for a Lambretta, but there are many variables besides that, often not taken into consideration. One major factor can be that of 'Operator Error' which is often the hardest for any of us to to admit
If in doubt, cane it with a healthy dose of revs is likely to cause far less damage than attempting to slog along in top
I have built mainly tuned engines in my time, the majority being for racing & with cast iron bores. Such a scenario allows no time for bedding in an engine, the only time being available being any practice laps. Yet, upon strip down, after some hard race miles, the bore & piston can look as good as any other top end that may have been nursed for a 1000 miles. I'm just saying.......