Honda-SOHC

The Middle groove of the five

Think we've all thought about that possibility at some point !
So long as the front run of the chain is in tension when the crankshaft is rotated and set (to mark T1 ? ) when the cam sprocket marks are aligned the timing will be correct. The slack at the rear/tensioner side doesn't matter at this stage.

For some reason I had difficulty refitting the camshaft last time and ended up removing the blade to get more room so the sprocket would slide over the shoulder. I like to leave the blade in place as it isn't easy to see down the tunnel if the engine is in frame .....long time back I removed one and it lifted the small holder piece out (in the arm) without me knowing.... ended up in the sump.

Heard about the blocked breather issue... with the cap open and the bike upright, being careful not to slosh fuel about too much you could test this?
Would have thought the engine would refuse to rev at all with a lack of venting.

Mine was getting bogged down mid range and the more the throttle was opened the louder the exhaust got with very little response.
Convinced it was running rich so I set the float height to 24mm ithen checked that the fuel level was about right at 7mm below the joint face.
This improved matters a bit but the air screws then had to be set to one and a quarter turns out for steady idle.. So much for measuring fuel level. Now running lean at idle?
Had to be something else that was worn or out of spec.
The only original items left were the needles and tubes so bit the bullet, replaced these and reset floats back to 21mm ... Better response and pulls in top. Idle screws are now at about two and a quarter turns out.
Seemed to be down to the air/fuel mix being off at partial throttle openings.

Well nearly.... you need to take the carbs off as a set then see what muck is lurking float bowls and address as above.
Re check the carbs for overflowing once they are clean and back together .....while theyr'e still off the bike , as putting them back on is the hardest part.

Ah... So you had tested it.
..so maybe worth blocking this off any way , belt and braces... Could be small leaks on many of these?.  May try this approach.

This hole puzzled me too,  when I re-cleaned the carbs yet again...
But they all have it 

I have a worn out No2 carb which I am looking at now ...... Sad !

The idle circuit takes a few turns and several holes are drilled to achieve this with some of them joining the others up.

On the outboard side you'll see the same cast feature but without a hole.
The drilled hole on the other side is there to connect the idle jet to the tiny hole inside where the fuel emerges.
It is then blanked from inside with a brass insert which you can see inside the float chamber, dead centre... see the line of the cast pipe on the inside.
Unless this tiny insert was blown out things are as they should be.

There are two more blanks in the chamber roof too.

Yes, take them to a specialist !
A very fiddly and tedious job.... Did speedo and tacho a while ago.

Got tendonitis from re-crimping the bands too !.... Have to say though, there are no marks visible from the top but on the underside the tell tale signs are there.

Wish I had re coloured the red line on the face
 while the tacho was apart though !