Blueprinting for methanol

Al, I was told the the 3 digit numbers on mikuni jets were flow numbers. I ended up buying a bunch of different sizes and sitting down with my pin gauge set and measuring them.
From the story that I've heard, the reason they do that is because they found that 2 jets, of the same size, will flow differently. The story I heard, go so far as to say, a smaller jet was found to flow more than a bigger jet when measured in the manner your talking about. Just a story I heard.

In my personal experience, when flow tested, out of 200 CNC machine jets, all the same size, (physically very similar to Briggs jets) the people I work for found that there were 12 – 14 different flow rates.

2 jets, .038" – .039", if you calculated it, there's a 5.3% difference in area (flow). That would cover 5 points on the air density scale. In that jet size range, .0002" in jet size would cover one point in the air density scale. That means, if you have a .038" jet in the carb, and the air density increases by one point higher, you would need a .0382" jet to compensate. In a perfect world. LOL it's. Regular pin gauges can't measure that small an increase. I have a. Spreadsheet to calculate all this stuff.

There are people, for reasons unknown to me, that don't like that.
 
And the surface finish inside the hole, (as well as minor differences in *length of the hole*) will also effect the flow rate.

There are bigger fish to fry -- like tires and handling.

imo
PM
 
It looks like I need to go back to school on jetting carburetors. All these years all I've done is put in bigger jets if it's too lean and smaller jets if it's too rich.
 
This is not an exact explanation, but this is the gist of jet numbers on a Mikuni carb. The jet number represents the quantity of fuel that will flow through the jet, gravity fed from a burette in a given time. So a 160 would be mL in a certain time.
 
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Metric to inch by .01 mm .89 to 1.0 20
 

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