83 yz490 jet needle help

[jaguarjx2]

I have a 83 yz490, I have done the head mod and am now trying to tune the carb.  I found some specs on the carb setup to tune it right.  It did not include what jet needle to use.  The from what i have found, I believe it uses a 6f16 needle.  I have some specs on the it490 for the same year and it say you need a 6f39.  So I was wondering if anyone had any input on my problem.  Below are the specs i found from another site.  Thank you for your help.

Jetting at sea level as follows:

Fuel mix 40:1
Pilot: 40
Slide: 3.5
Needle: Jet R-O
Needle: middle clip
Main Jet: 440
Note: Make sure you use stock reeds

[lms6201]

 6f16 , u seem to have the popular us setup , u may find u have to drop the needle one point , or go back to a q8 nozzle , how much meat did u remove from the head ? 

[jaguarjx2]

ok thanks.  I used a diagram i got online, I attached the picture.  By chance do you know what they mean by slide :3.5?

[SUZUKI311]

3.5 is the slide cutaway, call Ian Wiliams tuning in Adelaide, very helpful for Mikuni info, and he will have the necessary jets you need. All needle jets are different, and he will be able to advise you which series you need, and give a ballpark setting.

[Hoony]

please let us know if the head mod works, i have a mate with a 85' Air Hammer YZ490.