Even though the carburettors are identically jetted, IMO it looks like the rear cylinder runs a bit leaner than the front cylinder. Why? The rear spark plugs centre is lighter and the electrodes look drier than those of the front spark plug. Also, the wash on the piston crown is smaller on the rear piston which is because the piston is not cooled as much by rich mixture.
When checking the float heights a few weeks ago I noticed that one was a few tenths of mm higher than it should be while the other was considerably lower (but I had not made notes of which cylinder had which float height). I assume that a lower float (= lower fuel level) makes the mixture lean.
What I also noticed is that even though the porting is symmetrical, the piston wash is not. The left hand rear port seems to have little flow because there is little wash "in front of it" compared to the right hand rear port. I wonder whether that is by purpose.
Does anyone else have pictures of piston wash?
