Which stile of pilot jet for Mikuni CV carb

I noticed that there two distinct stiles of pilot jets for the Mikuni CV carbs. There is the BS30/96 with bleed holes and there is the N151.067 jet with out bleed holes. Everything I have read, states that they are interchangable. What would be the advantage of one over the other.


Post edited by: otakar, at: 2007/11/08 08:39

Without bleed holes

Otto - The second type without bleed holes is Mikuni type N151.067. These came in many OEM applications but are almost always replaced with the more readily available BS30/96 type. I use replacement pilot jets made by a company in Japan and they don't make the ones without the bleed holes nor are the ones without the bleed holes in any carb kit I know of (the folks who make the pilot jets I use also make the ones in the carb kits). You generally will only see #37.5 N151.067 type jets as these are the OEM Mikuni jets.

I have used both types and the bleed holes don't make a difference in these short jets. The reason for the bleed holes is to facilitate the flow of fuel through the small hole. This is why they added them to almost all bleed tubes (emulsion tubes aka main jet holder tubes). I read the scientific explanation once and the holes allow gas to pass through the small hole somehow more easily. I guess that since the pilot jets are only a 1/2" long, it must not make a difference. From a practical standpoint, I have used both type jets in the same carburetor and it didn't seem to make the least difference.

By the way, I use aftermarket pilot jets as they are far less expensive and work as well as Mikuni stuff for SOME pilot jet applications... like the BS30/96 type but on some other types, genuine Mikuni stuff has worked more consistantly better than aftermarket.

I would just add that having the bleed holes like that they would be less likely to plug up from dirt, as opposed to having just the one hole on the end.

Well, I ordered all the jets I wil ever require from "Sudco" for this bike. Pilots and Mains, I just wish I could change the pilot air jets if they were not pressed in.

You wrote, "I just wish I could change the pilot air jets if they were not pressed in."

The BS30/96 style jet is not pressed in. They screw in. There is sometimes a pressed in plug above the pilot jet to keep fuel from the float bowl out of the pilot jet well. This type of carb assembly has a cross passageway between the pilot well and main jet well and picks up fuel from the main jet well. If you have this type, there is a small hole about 1/2" down in the pilot/main wells you can see.

I ment the "AIR pilot" which is in the intake side of the ventury. I wish I could change that like I can on the VM33s. I did get all the jets in, and assembled the carbs today. I would like to mount them tomorrow and fire the bike up.