Actually, both throttles open up for accelerating. If you are seeing lean only on heavy throttle, then probably only the secondary side is running lean. But if you see lean on light and medium throttle, then the primary side needs to be richened. The Hitachi is tuned very much like a Weber 32/36.

Nissan supplied the jets. See Jets for the Nissan part numbers.

Thanks DD,
good straightforward advice as always..
I have looked for somewhere that supplys jets.... but not found any, do you know anywhere ?

would i need to replace both main jets, or just the primary? (or should it be the secondary choke that needs the larger jet as thats the one which opens up for accelerating ?)

Sounds good
* less than 17:1 for fuel economy cruising

Is bad
* accelerating, 13-15:1
Should be 12:1 to 13:1 for full throttle maximum power acceleration

Anything over 14.7 is lean, you don't want any lean while accelerating. For light acceleration even 14:1 can be too lean to run perfectly smooth.

Just fit main jets that are 2 numbers larger.

Fitted an AF meter last week, driving around this weekend these are the sort of results i get:
starting from cold (without choke), 12-13:1
running around town normal type driving, 14-15:1
accelerating, 13-15:1
Cruising at 80km/h in 5th gear engine revs about 3500 RPM , 15.5-16.5:1

Engine is std A14 but with header and K&N filter, carb is std Hitachi downdraft and is less than 3000 km old.
Is 16.5:1 overly lean and likely to cause any problems ?
Should i be looking to re-jet carb ?
Or is this just a case of too much information..