Knocking / rattling inside primary drive case + backfire

M-Hawk said:

No, from this compression TDC position with the timing mark off to the left I rotated the crank ANTI-clockwise until the timing mark came all the way around again. I did this because I thought I was supposed to move the crank in the direction of operation. Sounds like this was incorrect and is the reason that I'm out? Have I timed to Bottom Dead Centre?

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Yes, if you rotated the crank anticlockwise from TDC then the first rotor timing mark to line up with the scale would be the wrong 180 crank degrees out timing mark so the Wassell rotor position would then be approximately 90 degrees out.

L.A.B. said:

Yes, if you rotated the crank anticlockwise from TDC then the first rotor timing mark to line up with the scale would be the wrong 180 crank degrees out timing mark so the Wassell rotor position would then be approximately 90 degrees out.

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Ah, that explains (at least some of) it then. Thanks. I'll re-do it and report back.

I’ve just checked compressions. 115psi left and 130psi right.

Also, with my newly acquired boroscope (which is awesome by the way!) I decided to double check the fuel tank. Last time I flushed it, I couldn't really see inside.

Looks like the lining of the tank has gone. I think it's an Indian reproduction tank but the lining has been done very badly. It's pitted everywhere and there's quite a bit of rust. This could explain a lot of the problems!

Now on the lookout for a decent (genuine) 2nd hand Commando Roadster tank. Anyone got one?

The saga continues

Oh, my...

I have yet to see a tank liner that has survived 2 or more years of actual use.

Compression might be a concern. I assume this was done with engine cold so would be lower than when hot. I hit 150-ish when hot, throttle held wide open while kicking. Both sides within a few psi. That is the issue I see on yours, 15psi difference side to side.
Repeat check once you get it running and see if things even up some.
Are you running a fuel filter in the hoses to carbs? Helps keep crude out. I run the sintered bronze type, not the metal mesh ones. Cheap insurance at $15 for a bag of 10 on ebay.

Correction on the compression. I suddenly realised that I didn’t have the throttle open on the left cylinder test!

I’ve just re-tested and got 130 each side. Phew!

Tested cold, by the way.