I F'd around in the shop a bit today after I took my dad to the hospital for his ultrasound.
I started with that vacuum fuel pump my brother bought for his machine.
Will save that nightmare for another thread.

Then I moved on to trying to figure out how much a main jet will flow.
The info online is a joke. So if I'm going to read about a comedy show then I might as well be the star.

Method:
1) Took a 350 main jet and stuck it in a clear hose.
2) Mounted this hose on a regulator.
3) Hooked the regulator to a water hose.
4) Set the regulator to approx 5 psi. --- Why did I choose 5 psi ?? Because I measured the crankcase pressures a long time ago. My Engine (basically stock) had 5 psi pressure and 5 hg vacuum. My brothers machine (super Engine - ports,pipe,2mm shaved cyl, etc) had 5 psi pressure and 7 hg vacuum.
5) Stuck the main jet hose into a measuring container and turned the water on.
Measured for 10 seconds approx. using a stop watch app on my phone.

Disclaimer:
The gauge on my regulator started at 10 psi but you could guess at getting 5 psi based on where the needle was sitting. Obviously not 100% accurate but close enough.

Results:
350 main jet
4.5 oz in 10 sec approx.

Why did I do this ??
Lots of talk lately about how much fuel is required for these machines. I was curious.
So I looked in the manual and it said the oddy tank is 3.8 us gals. That's 486 oz.
If this 350 jet uses 4.5 oz in 10 sec that's .45 oz per second at 5 psi pressure which is what our engines pull.
486 oz divided by .45 is 1080 seconds.
1080 seconds divided by 60 equals 18 minutes.
No way in hell do we only have enough fuel for 18 minutes of riding.
So what is going on here ??
Well the way I see it is that we actually at best only pull half of this rate at full throttle. That's because the engines only pull fuel when the piston is coming down and when it goes up it slams the reeds shut and is not pulling air/fuel through the carb.
So if we double this 18 minutes we get 36 minutes of riding. Clearly we get more than that right ??
So at the end of the day, even at full throttle we are good with this 4.5 oz in 10 sec flow rate.
By the way it's shocking to see that amount of water come out of that jet. Scary.

You guys can laugh at me and my comedy show up here in the great white north but I have a good time.
CO

Thanks for taking the time to do this CO.

You have to add the pilot jet into the result.

Also the needle jet and needle will change that flow rate as well. Also it’s vacuum across the Venturi that pulls fuel. It’s not pressure.

Finally and since you are on to something, measure the fuel flow through a spare needle/seat. Actually the NS should be a higher number than your combined jetting else fuel will struggle to enter the carb.

I love reading about all your experiments, I think your screen name should be ''The Professor''..lol

Considering these pumps are used in 1000cc applications, I never thought there was any need to worry about the amount of fuel they can deliver.

The low pressure pulse style electric pumps were used on super sport motorcycles for years. The bottom of the tank was lower than the carbs, so they used these pumps to fill 4 carbs on an Engine that revved to 14000 RPM. Pretty sure that's plenty to keep an old fl350 running.

And correct me if I'm wrong, but isn't the stock fl350 pump kind of like what you would see inside a jetski carb? There were plenty of 2 stroke 750cc 900cc jetskis running carbs back in the day.

Exactly.

I had a leak at the petcock. The tank was completely full. I disconnected the fuel line at the carb and used the electric pump to transfer fuel to a can. I didn't time it but it didn't take any time to get the fuel level below the petcock. I guarantee you there is no possible way that the Engine could use the amount of fuel the pump produces.

All 2-stroke jetski carbs still use mechanical fuel pumps today. Yamaha still produces a 2019 Superjet which uses the same Engine from ~1996. Thing is no one pump is the same. In jetski world, the old round-body fuel pumps from Mikuni were junky, but the Mikuni square body pumps are very capable. Keihin carbs are out there in skis, but honestly no-one uses them much due to tuning issues and popularity. The mikuni carbs and pumps are a much better design for performance tuning.

I'd trust a Mikuni fuel pump over any other mechanical pump on the market at this point. I had some faith in the Polaris pump, but seeing first handed how flow deteriorates over time is mind numbing.