Mikuni side mount pilot air screws

Ok, here's a scan of the pilot diagram from my manual, but I need help interpreting it. It isn't exactly like either of the diagrams Patton posted earlier.



It looks to me like turning the screw in would restrict the amount of fuel going through the "Pilot Screw Passage" (#4) thereby making the mixture more lean.

That would mean in for lean, out for rich. Is that right?

Topper wrote: Ok, here's a scan of the pilot diagram from my manual, but I need help interpreting it. It isn't exactly like either of the diagrams Patton posted earlier.

Attachment pilot.jpg not found

It looks to me like turning the screw in would restrict the amount of fuel going through the "Pilot Screw Passage" (#4) thereby making the mixture more lean.
That would mean in for lean, out for rich. Is that right?

Thanks for posting the diagram.

That would mean in for lean, out for rich. Is that right? YES! I concur.

The #3 pilot screw adds fuel mixture to supplement the #5 pilot bypass

Good Fortune!

Well damn. I'm back to square one on tuning these carbs then.

With size 45 pilot jets in I had both pilot screws almost all the way in so I decided to go up to 50s. But I had it all backwards.

I guess it's back to 45s (or maybe even 40s) and I'll look to the needle position to resolve my problems.

The bike actually had 40s in it when I bought it and it popped a lot, was very sensitive to cold and several folks on KZR were recommending going up to 45s for these 750 twins.

Now I'm thinking go back to square one, put the 40s back in and so long as I can remember "in for lean, out for rich" I might be able to tune them properly.

Thanks!

IIRC there were 2 different jet needles used on the 76-79 KZ750 carbs (BS38s)one is slightly leaner than the other. So depending upon which you have you may want the 40 or the 45.

As I understand it below are the stock settings/jet sizes.

Type BS38 1976-1979 KZ750B1-B4

Main jet 125
Main Air Jet 1.0
Needle Jet Badge # Z-4
Jet Needle 4JN19-4 or 4HL12-3
Pilot Jet 45 or 40
Pilot Screw 1 1/2 + - 1/2t turns out
Starter Jet 110
Fuel level (from bore center) 31 ± 1 mm
Fuel Level 4.5mm ~ 6.5mm