I recently inherited one of these in a Serpent 966 and have run it a few times on the track now . I like the power band, very smooth, and has good runtime around 6mins with 8.5 restrictor. It has the 2015 pipe, with short header.

I have been running 25% Nitro AT Platinum Fuel in it, which I understand is 10% Synthetic Oil only. I use the Nova C7TGC plug.

My background is 1/8th offroad, with OS engines, so I have a reasonable handle on tuning, but not Novarossi style carbies.
With the engine warm, it will idle reliably for maybe 20 secs or more, and pulls away cleanly, with some smoke up into 2nd gear. Our track is mostly tight, with a long straight along the back.
After several minutes of racing, I intermittently experience a 'lean bog' out of one particular corner just 2 bends after the main straight.
I'm assuming I'm a little bit lean on either the top or bottom, but when I richen the either needle ever so slightly, it seems too rich, and won't pull away cleanly or top out properly??

I'm aware the Centax clutch might be causing this, but it operates perfectly elsewhere on the track. This problem occurs only on the same section of the track.

The only other factor i'm thinking about is ambient temps. It has been down around 15 degrees (winter here in Australia) and I've not tried any warmer plugs??

I did try some 20% nitro fuel, but the same was occurring.
Any helpful hints are gratefully received