TOPIC:

Seems my enthusiasm for the MIG tip choke Air mod. got the better of me.
So please note: I indicated I drilled the MIG tip to 1/8".
Anyone see the problem ?
Tube is measured O/S dia. !!!!
The Tip should be drilled to 3/32". This is the I/S dia. of 1/8" brass tube !

It was a PM question I found this a.m. that re-enlightened me to my error but went on to ask if another diameter might work? Maybe ! Don't know. The restrictor size of 3/32" I/S dia. works well enough for myself and apparently for stan that at this time - I'm leaving mine (silicone/brass) as is.
As kawboy indicated - with the MIG tip mod. - the restrictor dia. can be what ever you drill it to. Personally, I wouldn't consider going smaller as this would likely make the choke circuit too rich. Going bigger? May defeat the purpose/advantage.

.....carry on !

Kawboy wrote: What are the chances of drilling and tapping for a main jet now that you've proven the theory that a reduction in that port is a viable option?

In keeping with his idea of a more "factory" appearance and preferring the flexibility of using a range of orifice sizes I did some digging and found that Holley has jets that have a 1/4"-32 thread and are available with a .094" orifice which matches the 3/32" that I've suggested.

So for you experimenters - fill your boots because they have a wide range of jet sizes to drive you nuts.

What scream. I ordered 3 of these this morning !!
Mikuni B42/55 size 280 jets

Hi Scotch,

for the rest of the world 3/32" is 2.38mm. Would you recommend drilling to 2mm or 2.5mm?

for the rest of the world 3/32" is 2.38mm. Would you recommend drilling to 2mm or 2.5mm?

3/32" or 2.38

No More - No less

This is a repeat of what I posted in "Kawboy's Restoration of a B2"

Popped the lid of of the carbs and started the mod. The thread size on the B42/55 is a 6mm x 1mm standard thread. The tap drill for that thread is a #9 which is .194" I measured the bore of the air jet in the body of the carb at .191" so there was no reason to have to run the #9 bit in the hole, just tap it out to 6mm X 1mm. Tapped it in 5 threads, cleaned the hole with a vacuum and pulled the choke plunger out to ensure no aluminum thread filings. Inserted the jet and Bob's your Uncle. So I've choked down the air to the choke circuit from .191" to .110" using the B42/55 X #280 jet.

I also like the nice clean look. If I decide down the road to change the orifice size, the B42/55's are available in #70 (which is .7 mm) to #290 (which is 2.9 mm)