Carb jetting

I recently checked the size of jetting by pin gauge , found there are bigger than there are marked.

eg. marked 1.30mm → actual 1.40mm

Around 8 ~10% of gap.

Is it for safely sake or just simple inaccurate at proceeding?

There’s some discussion on this in other threads. Essentially, most will not measure exactly as they’re stamped, but usually they will pin at a consistent differential above the respective marked sizes. This really only matters when you’re jetting at the razor’s edge, and a ~3% inconsistency may cause you to miss your target jetting.

there you are sir

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Thank you, interesting topic…

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Coffee Smile GIF by Yellowstone


Yes, could be an issue.

I found a varience of 8-10 jet sizes in my jets.

But they were fairly consistant in the varience, although some jets were identical.

For example a 178 and a 172 were the same size.

Worth charting the jets in my experience. One less varible to rule out.

We have seen difference In 6-10 sizes on Dellorto jets, with sizes all over the place.
Best solution is to make a set with meassured jets that you know the size of.
We have a set of jets for each carb, this way we never loose track of whats installed In which carb.
Another solution is to have a jet kit where you have every second size of jet, this way you are fairly sure that you know a size 130 is bigger then size 128,

Yes, I am keeping them in the right box after meansured.