wb wrote:More of a four stroke concern really (esp without a slipper clutch), but I do do it when there's the opportunity if running premix - just to get a bit more lube in there...

I've been working with Ian Emberton (IanE), an experienced Honda RS engine man in the UK. Ian said he has known big downchanges on closed throttle to, in some cases, cause piston & ring damage. As its on premix, there is a break in lubrication supply on a closed throttle. A big downchange through several gears will see high engine load fall and rise again suddenly, which is when you need that lubricating film between piston & bore. However, the racing 2T oils do have a good ability to maintain a film, which is probably why the problem is not seen all of the time.

Obviously no issue when running an oil injector, which delivers oil even on closed throttle, albeit at a reduced rate.
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Rich
MC21 Track Bike / RS250 NF5 'Spencer', NX5 'Cadalora' & NXA 'Aoyama' / RS500 / Two Brothers Racing RC30