6 replies to this topic

[croc7]

I am confused with the graphics on the mintylamb.su site. What do the numbers represent? The vertical lines-stations of the needle? If so, the upper right side of the graph line would be wide open throttle, the slimmest tip of the needle? I’m trying sort out using BCE, BDK or BCP needles on torquey 1360. The on-the-road testing using an AFR sensor don’t jive with how I’m reading the graph. HIF44 using Redline 20w for the piston damper oil with red spring.

[nicklouse]

I would suggest taking a screen shot then everyone can see what you are looking at.  It will save any confusion in the interpretation of the graph.

[Spider]

Each Vertical Line represents a 'Station' as it's called or put another way, a point along the needle where it's dia is measured. Each Station is 1/8" apart.

I see there's now a few ways it will display the needle profile numbers;-

 

Dia of the needle at that station point in mm

When fitted in a Jet (as it would be when fitted to the carb), the area that is open for fuel flow in sqmm

 

These are selectable.

Most people tend to work from the Needle Dia at each Station point.

 

Here's a diagram that shows each of the Stations;-

 

 

[croc7]

Thanks Chris, any chance that you would have a similar diagram for HIF44/HS6 swing needles?
J

[nicklouse]

Thanks Chris, any chance that you would have a similar diagram for HIF44/HS6 swing needles?
J

It is the same idea. And the measurements depend on the needle. And that can be read of the info on Minty Lamb.

 

if you don’t understand what you are looking at post up a picture of it then we can comment on it. As if I remember correctly there are options on how you can configure the graphs.

[timmy850]

Heres the screenshot of the BCE needle with the setting in mm. The left side is the thick end - which is idle and low speed. 

 Screen Shot 2021-04-09 at 7.12.54 PM.png   141.43K   7 downloads

 

Classic Mini DIY also has a similar comparison

https://www.classicm...chnical/needles

 

And if you want to really get into it, there's a comprehensive spreadsheet a guy has made here

http://mk1-performan...hnical_carb.htm

[Spider]

Thanks Chris, any chance that you would have a similar diagram for HIF44/HS6 swing needles?
J

 

Sorry to say no, none to hand, but as Nick mentioned, it is basically the same for these, the Stations are 1/8" apart and the general function of each 'section' of the Needle is similar to that diagram I posted up, however, all these diagrams I've seen show the 'Pick-up (acceleration) and Cruising ' section confined to a general part of the needle however, in reality, this is from Idle all the way to 'Top Speed' (which is actually Peak Power).

 

Sorry to go a bit off topic here, but it raises a point regarding Carb Modification that I've read of on the forum.

That the 'Pick-up and Cruising' parts of the Needle are inter-twined also show why from road use the Internals of the Carbs should never be modified. Fueling (Carb) requirements between 'Pick-up' and Cruising are very different, yet they have been designed as such that a very close balance is reached between these two conditions. Modifying the internals upsets this balance, resulting in condition where say a needle is selected for clean Pick-up' it may well end up being Rich on the Cruise, of if it's selected for optimum for Cruise, it will end up Lean on Pick-up. There's a few books about that show and suggest internal modifications to these Carbs, however, that's generally aimed at a class of racing where changes of carbs is not permitted and Cruise requirements are not a consideration. For just about any other application, when one is looking for an increased Air Flow through the Carb, you'd just go up a size (or two), or go to Twins etc.

 

Back on topic;-

I did mean to mention here too that Minity Lamb seems to only display the diameters or orifice area in metric numbers. Traditionally the Diameters have always been measured in imperial numbers in thousands of an inch, so if comparing Minty Lamb to a book or chart of Needles you may have, you need to keep this in mind.