Carb Needle Jet markings

[disc_valve]

Hi, Folks,

I've been scratching my head over this problem for a while. I have a three genuine Mikuni Needle jets for the VM15 carb (as fitted to the BS50/60 Sport and BS90 90 Deluxe). They all have different markings on them, but are all the same physical dimensions (so far as I can measure with a Vernier caliper).

Does anyone know what the markings on these jets mean? The factory needle jet is marked "E-0 #110". The other Needle jets are marked "E-0 #165" and "D-8 #110". Can anyone decode these numbers and tell me what the differences are?

Graham

[BRT-GTR]

Hi Graham,
                You're joshing us aren't you  . We ask you questions like this, if you don't know, what chance have we mere mortals got  

  I'm certainly no expert on these carbs. If you Google (other search engines are available ) Mikuni Carbs , two sites seem to give good information - Motocarb and Mikunipower.

 From what they say the 110 & 165 is a Series number which is linked to the carb throat diameter and carb type as shown below -

           http://www.motocarb.com/mikuni-needle-jets.html

   The E-0  &  D-8 indicate the internal bore of the jet as shown by the table at the bottom of the page above, unfortunately it doesn't cover the smaller size range .
  From what I can see, I guess the 110 jet would be for the 50/60 engines and the 165 jet for the 90 engine but I can't be sure.

  The Mikuni power site does show information on the smaller carbs now available and has a Tuning Manual section (as referred to by Karl) below -

        http://www.mikunipower.com/VM01.htm

  Hope this sheds a bit of light on the issue. Brian.

[OldSwartout]

The Sudco catalog shows the general pattern for the Mikuni needle jets, however it doesn't show ones this small.  The pattern is the size increases with letter and number, meaning an E would be richer than a D, and an E-2 would be richer than an E-0.  The 3 digit numbers are "series", which seem to relate to variations in the carburetor design they were use in.  If you can find someone with a Mikuni Tuning Manual, there may be more specific info.  There was one in our family, but I don't know where it is currently.

Edit: I see Brian posted while I was typing. 

[disc_valve]

Thanks for the pointers, Boys

I had guessed that one of the markings referred to the size, but I thought it would have been the "110" bit. WRONG!!!

Seriously, though the info does make sense. The jet marked "i65" is a later type that takes a post-1969 type round-headed main jet (different thread sizes), so that would indeed be a later series than the "110".

Of the three types, the original Bridgestone jet is the  "E-0 #110" , and the same jet is fitted to the 50 Sport, 60 Sport and the 90 Deluxe/Trail/ Mountain models.The Jet marked "D-8 #110" came from a Yamaha YG1 carb that I acquired for parts. That would  be the same series as the correct BS jet, just a couple of steps weaker. I had no way to measure the bore of the "jet" section, hence I was unable to see any differences between them.

I've printed off the website pages for future reference, and I've learnt something new today.

Just goes to show what a great bunch of guys (and gals) we have on this site.

Cheers!

Graham