Pilot jet differences?

[Vulpine2]

Been playing with two different sets of 40mm Bings over the last week, one from a r100r and one from a similar age r100gs. Both bikes are from 1991/2.
I have only just noticed that the pilot/idle jets are different - identical bar the number of bleed holes in the base. One has six, the other only one. Anybody know why and/or what effect the difference would have?

 

[Gelandestrasse]

Interesting. I don't know the answer to your question but looked up that the 45 idle jet is common to most models/years and comes in 2 lengths, 23 and 26mm, not interchangeable (according to M.Works). But they both have multiple holes. Two guesses though - one, yours are different sizes (not both 45) and two, the one with one hole is a very early part which was phased out later and you can only buy multi-holed ones now.

Someone will be along soon with the correct answer.

 

[Vulpine2]

They're both 45 & both 26mm long.
I've just had a look at some from an '89 bike - and they are the multi hole ones. Which suggests that the single hole ones may in fact be the later ones?
Proper top level anoraking...

 

[Gelandestrasse]

I think you'll need to carbon-date the brass to find out!

 

[Mad Hatter]

Is this any help?

 

[Mad Hatter]

Is this any help?

View attachment 338744View attachment 338744

Here is a link to the table

https://bingcarburetor.com/uploads/9/8/7/9/98794296/bmw_jetting_chart_cv_carbs.pdf

 

[SteveHop]

Vulpine 2 ,you have to find the specific carb numbers which are stamped on the side of the carbs and then cross reference these to the chart for the correct pilot jet . For instance , 90/40/123&4 has a 45 pilot jet.
If you change the jet size then you will have to readjust the idle mixture.