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Sat Sep 28, 2024 10:46 am

I just noticed this, as I was looking at the blue dealer service manual.
Will having the wrong direction flow main jet effect performance? :?

Sat Sep 28, 2024 12:43 pm

It probably has to do with the lead in chamfer and/or how they were drilled flow tested when the jets were made.
(yes OE production jets were flow tested, tho probably just with air, it's easy to do with mass production)

Many years later it's not going to make a lot of difference. Very old jets are often way out of calibration anyway. Corroded smaller or eroded bigger.

But would be interesting to examine the lead in and lead out angles, I have no idea if they are different or not, I suspect not, but could be wrong.

According to Holley a jet with a sharp/square entry flows less at higher demand than one with a 45 chamfer, and such odd jets were used a few times in certain models.

But I bet solex was just making sure to drill them in the direction of flow so that any small burr from final reaming would be on the exit, where it would not change the flow as much.

Sun Sep 29, 2024 7:20 am

I tried looking with a magnified glass, to see if I could see the difference, but couldn't.

Sun Sep 29, 2024 11:22 am

Now, I have not seen everything. But i have never seen a Solx jet which flowed the opposite direction (!)
There are Solex jets for gasoline and for air, yes, but they are different and not interchangeable.
Main gas jet: https://encrypted-tbn0.gstatic.com/shopping?q=tbn:...JSrdI6VQAl
Solex air jet: https://encrypted-tbn0.gstatic.com/shopping?q=tbn:...SFnlln7wIE

Mon Oct 07, 2024 12:13 pm

Alstrup wrote: Now, I have not seen everything. But i have never seen a Solx jet which flowed the opposite direction (!)
There are Solex jets for gasoline and for air, yes, but they are different and not interchangeable.
Main gas jet: https://encrypted-tbn0.gstatic.com/shopping?q=tbn:...JSrdI6VQAl
Solex air jet: https://encrypted-tbn0.gstatic.com/shopping?q=tbn:...SFnlln7wIE
Why would solex put x/o on the jet, if the main jets look all the same? The solex air jets are easy to recognize. Thanks for posting the photos.

Mon Oct 07, 2024 12:55 pm

Because in the old carbs the main jet flows backwards from normal, but the same jet can fit many different models.

The ones with the main jet in a brass holder, fuel goes in the threaded side and out the head side.
Never thought about it? :wink:

Mon Oct 07, 2024 1:46 pm

modok wrote: Because in the old carbs the main jet flows backwards from normal, but the same jet can fit many different models.

The ones with the main jet in a brass holder, fuel goes in the threaded side and out the head side.
Never thought about it? :wink:
True, about the main jet in the brass holder. Now we know.