Carbs off is no big deal especially on a '21, it's far worse on a '28, you really need to drop the fairing to get to the l/h carb clip, the hole in the plastic bit isn't in quite the right place and it's much easier to get to if you undo the overflow bottle mounts, the needles are a right pain to get out as well, Steve and Andy did them in situ but on your own it's a carbs off properly (as in totally disconnected from the bike and get them on a table) job then mess about with the carb link so you can get the needle holder out properly.

It's only an hours job though, I guess it depends what your used to, back in my boy racer days a camshaft change on a 2 litre mk1 or 2 Escort (which was a far too regular occurance as the hit or miss lubrication of the Pinto cam is it's weak point) entailed removing the head which clearly costs money and risks getting bits in the oil or, either dropping the entire engine and gearbox assembley (or lowering the engine crossmember), spliting the engine from the box and removing the engine as the cam although it's an OHC engine comes out backwards
I've seen 2 litre petrol Transit's with a hole in the bulkhead to get round this problem
My Transit needs doing right now, I heard it start to tap a bit on the way back from Steves after the Chelsea rideout and it's now quite bad, there's nothing you can do about it (apart from buy a cross drilled race cam), it's just a poor design, now that is a rubbish job, the NSR is heaven to work on next to it.
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Please do not PM me technical questions, if you can't find it on the Forum start a thread