Nozzle & Exhaust jet questions

*13* · #1 (**permalink**) 07-02-2015, 06:51 AM

I'm ready to start messing with my acc circuit. I have the stock 50mm nozzles & the 00 exhaust jets. Id like to get the nozzle size correct, first. However, thats a pretty big investment to start going down the chain, size by size. & I don't find this a very readily available part unless I just want to go down one size to 45. Thoughts? It's definitely too rich on the squirt!!!

jhirasak · #2 (**permalink**) 07-02-2015, 08:24 AM

If you are sure that you are too rich on the squirt, I would recommend that you increase the exhaust jet size instead of changing the nozzle size. It is also less expensive to replace the exhaust jets since there are only four of them as compared to eight nozzles. However, replacing the exhaust jets are a bit more trouble since they are located in the main body below the float.

Right now, you do have zero bleed so all of your pump volume is delivered with each squirt. As a starting point, I would recommend a 0.50 exhaust jet and then you can either choose a larger exhaust jet if the shot is still too rich or choose a smaller exhaust jet if you get a slight stumble upon acceleration.

*13* · #3 (**permalink**) 07-02-2015, 08:30 AM

Is it possible to drill the exhaust jet? I know they have a ball inside & the hole is on the side. Or could this interfere with the ball movement? I do know it's pretty rich. I may start more in the 20 range, if I can drill.

jhirasak · #4 (**permalink**) 07-02-2015, 08:56 AM

I would not recommend drilling the exhaust jet since it contains a check valve and any trash from drilling could affect the ball seating. As I recall, the exhaust jets were not very expensive.

There is another advantage in having an open exhaust jet instead of the standard 00 closed one. With current gas formulation containing some ethanol, there is the chance of fuel percolation in the accelerator pump chamber causing fuel to drip out of the pump nozzles and into the throats after hot shutdown. Having an open exhaust jet allows any buildup of pressure in the pump chamber to bleed back into the fuel bowl instead of causing fuel to drip out of the nozzle.

With my Webers which came with a 00 exhaust jet, I changed to 0.35 and then to 0.50 which eliminated the fuel percolation problem while still providing enough fuel delivery to avoid stumbling during acceleration.

*13* · #5 (**permalink**) 07-02-2015, 09:01 AM

Interesting. I guess that explains a few things. Thank you!

jhirasak · #6 (**permalink**) 07-02-2015, 11:30 AM

Hyde,

I sent you a PM with additional comments regarding accelerator pump jetting. I hope that it helps.

John