I need some jetting help please

[Sollie1986]

Hey everyone,

I'm scratching my head right now cause I'm not getting any success with my current motor setup. I live in Colorado and I'm running an 04 motor stock bore with a cp 13.5 piston, the head was ported by dasa along with +2 exhaust and +1 intake valves, web 208/921 camshaft, 40mm fcr carb, duncan fat boy 4 exhaust, and an open air box with a k&n. I can get the motor to idle, but only if the choke is pulled out. Once I turn of the choke I can keep it alive while messing with the throttle, but it backfires and has terrible throttle response.

I ripped the carb apart and cleaned the crap out of it and here's the numbers I'm currently set up with

Main-#172
Slow-#52
the other tiny jet is a #80

Any suggestions would be greatly appreciated. Thank you.

[audioworks04]

Was there actually alot of crap in your carb? If so, I would clean your tank and clean your carb again really really well. If it will only idle with the choke on, then that means it is rich in the idle circuit, so bumb you pilot down to a 50 and see where that gets your. Im not sure about your elevation, but I would think you are on the lean side of your main jet. As far as your leak jet, sounds large, but I run an r&d adjustable, has been a while since I messed with them.

[Sollie1986]

Yes the tank and the carb have been torn completely down and cleaned thoroughly. So I should try going smaller on the pilot jet, and possibly bigger on the main jet?

[DnB_racing]

also be absolutely sure there are no tears and that all your rubber boots are not leaking air from not being installed properly,or you'll cook your new motor in no time, not to mention it will run like crap

and I second previous post go smaller on pilot go smaller on leak as small as 35 and start at a little higher on the main
and work from there

[Sollie1986]

Great advice, I did double check the rubber boots and they are still operational. Can I ask what the purpose of the leak jet is? What will I notice when it is changed?

[DnB_racing]

Originally posted by Sollie1986
Great advice, I did double check the rubber boots and they are still operational. Can I ask what the purpose of the leak jet is? What will I notice when it is changed? The leak jet is a like an orifice in the passageway what limits the amount of fuel that is bypassed to the float bowl.

The smaller number leak jet will:
Allow less fuel back to the bowl thus more to the Accelerator pump nozzle.
The larger number leak jet will:
Allow more fuel back to the bowl thus less fuel to the AP nozzle.

[Sollie1986]

Got it, thank you very much. So is there a possibility if the leak jet is reduced it will run rich, which in turn will eliminate the need to up the size of the main jet?

[DnB_racing]

Originally posted by Sollie1986
Got it, thank you very much. So is there a possibility if the leak jet is reduced it will run rich, which in turn will eliminate the need to up the size of the main jet? no the leak is for the accelerator bypass only.. it doesnt have any affect on the amount of air that is mixed with fuel

by reducing the size it will eliminate the bog when you jab the throttle by having enough fuel in the acc pump diaphragm housing and not dripped down into the the bowl... but have absolutely no change to jetting

[Sollie1986]

Ok, thanks for the clarification.

[Sollie1986]

So, I am not getting any success with this thing. Im wondering if im not going radical enough with my jet variations. I have not seen a single change in how it runs with any combination of these jets. Everything is cleaner and sealed better than a ducks ***** hole, but it still wont idle with the choke off and it is still back firing when it decelerates. Here's the numbers I've tried so far.

Main jet- 172 175 178

Pilot- 52 50 45

Leak-35

Needle- Is set at half.

Any other suggestions would be very appreciated.

[quad71]

There is also a fuel screw adjustment it helps with idleing. pilot and fuel screw control idle. If you have to have the choke on your not getting fuel. choke opens up a jet letts more fuel in. the hot start opens up and letts air in. you could have a sticking hot start.

[Sollie1986]

Ya, I just bought a brand new air/fuel screw today cause my old one was missing its rubber seal. Anyways, I took the hot start apart and cleaned all that.