Carb setup advise - Newbie question

[Gripperod]

I have just taken over looking after my dads A7, it has had very little use in the last 12 years although it has been kept on the road. I am trying to get the carb set up and need a bit of advice.

• It is a 1959 A7SS.
  Completely standard apart from some recently fitted Spitfire Scrambler Pipes, SRM bottom end and SRM valve seat work - The pipes have not noticeably affected the carburation.
  New Monobloc Carb with standard jetting was fitted 34/4 years ago (about 200 miles!!!!!)
  Carb has been stripped and cleaned.
  Just between 1/8 and 1/4 the bike runs rough and then clears as the throttle is opened and the revs rise.
  I cleaned the plugs, went for a 10 mile ride and then checked them (photo attached)

Any advice gratefully received

[muskrat]

G'day gripperod,
                      sorry I don't know much about monoblocks but 1/8 to 1/4 is mainly controlled by the slide cutaway.
Could be an air leak, check by spraying some WD around the flange, if revs drop thats the problem.
Do a plug chop at the problem throttle opening. Google "plug chop"
Plugs look a bit lean to me (air leak)
Cheers

[wilko]

If you have a choke fitted, try partially closing it to see if that improves it?

[Gripperod]

Muskrat,

I am super impressed, you somehow managed to diagnose the problem from a mere 10631.661 miles away! (Approx). I squirted some WD as you suggested and I thought there was a minor difference so (As a temporary bodge honestly....) I ran some silicone round the edges of the Carb gaskets left to cure for a while and then took it for a test ride. Whilst the  overall fuelling still isnt quite right, the flat spot at 1/8-1/4 throttle has gone!!!!!! I would NEVER have thought about an air leak.

So this weekend the carb is coming off for a careful inspection and refit.

Any tricks of the trade required for fitting a carb and ensuring no leaks?

Thanks again

bp

[Triton Thrasher]

You can't ride an old bike and not suspect inlet air leaks!

[Gripperod]

Ah well, older and just a little bit wiser! 

[a10 gf]

You can't ride an old bike and not suspect... magneto\carb\valve\clutch\braking\gearbox\oil leak\bearing\charging problems lol. The pleasure is in fixing them, and then ride the bike.
Glad you got help on the forum.

[muskrat]

G'day again,
                glad to help. A quick fix is to smear silicon around the joint and start the motor straight away for a minute, then let it cool. The silicon will be drawn into the gap and set. I can still see the remnants on the '51 after a few years so it still works.
Cheers