Mikuni needle jet bore sizes, 159 type

[John Orchard]

I'll post this here, it took me long enough to find it, sure there is someone out there that has a more complete listing. These are for the 159 type needle jet for Mikuni VM30, 32 & 34, not sure if the sizing correlates to other models.

Description codes & bore sizes.

O-4 = 2.620mm
O-6 = 2.630
O-8 = 2.640
P-0 = 2.650
P-2 = 2.660
P-4 = 2.670
P-5 = 2.675 (half size)
P-6 = 2.680
P-8 = 2.690
Q-0 = 2.700
Q-2 = 2.710
Q-4 = 2.720
Q-5 = 2.725 (half size)
Q-8 = 2.740
R-5 = 2.775 (half size)

I thought I'd have a play drilling out some needle jets but I don't own any equipment exact enough :-) I guess I just wanted to know if the bore size was the only specification that changed with the description code. In a pinch, if I needed a richer 1/4 throttle (the point where the needle jet bore size and needle straight section are in play) I'd consider reaming out the needle jet ID with some tapered jet reamers I have. Being the butcher that I am ;-)

[PeterC]

Thanks for that John. Sometimes getting hold of the correct information is worse than pulling teeth. The sizes mean more than model nos

[Tomas]

Hello
This web site also has a needle jet chart.
https://www.thumpertalk.com/forums/topic/1224849-mikuni-tmx-needle-decoding/
Need to scroll down about half way. I got a good result drilling out not sure what size needle jet to size S-0 just by using a 2.8mm drill bit 

[John Orchard]

Hello
This web site also has a needle jet chart.
https://www.thumpertalk.com/forums/topic/1224849-mikuni-tmx-needle-decoding/
Need to scroll down about half way. I got a good result drilling out not sure what size needle jet to size S-0 just by using a 2.8mm drill bit 

Interesting, thanks. Looks like the sizing code is used across multiple jet styles.

[Momus]

Hello
This web site also has a needle jet chart.
https://www.thumpertalk.com/forums/topic/1224849-mikuni-tmx-needle-decoding/
Need to scroll down about half way. I got a good result drilling out not sure what size needle jet to size S-0 just by using a 2.8mm drill bit 

Ditto for similar job.
Used a drill a size under then finished to size.