Thread pitch on 4mm air jets - Dave F mod.

[IR8D8R]

I have a box of small drill bits with no numbers stamped on them. I used a metric mechanical caliper (no dial) to choose one around 2mm to drill the air jets on my stock carbs. Measured the shank and the flutes. 2mm... I ordered threaded air jets in 2mm to cover my a** in case of error. In checking myself I discovered that the bit I used will not go into the 2mm air jets so perhaps I erred in choosing my bit. Dunno...

The instructions for the Dave F. mod in the Tech says 4mm tap to fit the screw in jet but no thread pitch. Anybody know the thread pitch of the replaceable air jet? Will a 0.05-0.10mm oversize affect the outcome? Can I tune around this?

IR8D8R

[m in sc]

i cant speak to the pitch of the airjet, i think its (4x0.7mm). however, you can in the meantime use a 5/64" drill bit in the airjet and it will tune right. (2mm= .078739, 5/64"= .078125)   

[Robert58]

Here you go it is 0.70 thread, this is from Dale Alexander instruction  mods

Purchase the 2mm correction jet from Sudco or
Rocky. Buy a 4mm X.0.70 tap and a number 30 drill. Use
http://www.saltmine.org.uk/dale/dale-faq.htm
the drill to drill out the stock .6mm air jet Fig 2. The
drill should catch the air jet and spin it out. Use the tap
drill to tap threads into the new hole. Stop when the
tap gets tight as it should bottom in the hole. When
finished, insert the 2mm air correction jet and marvel
at how easy it was to turn a street bike carb into a carb
with a racing heritage!

[IR8D8R]

Thanks Robert!

IR8D8R

[Robert58]

Your Welcome, I drilled and tapped threads and  put in the 2 mm air jets . I was not hard . Good luck!