I just had a quick question in regards to tuning.

So when adjusting the idle mixture screw and going clockwise, I'm making mixture lean by introducing less air, and this is audible because the engine will stumble and die. If I go counter clockwise, rich, I should hear the engine pick up speed then stumble and eventually die.


My question is when I'm aiming for the rich side of the turn, is my stopping point the moment it picks up in rpm or right after that increased rpm when it begins to rich stumble?

 

Watch the slot on the needle as you turn it, turn it down till it fumbles they turn it out6 till it starts acting fat them set the needle halfway between the two spots with just a hair to rich side, not too much. Should be about 1-1/2 turns roughly from lightly seated. If it's more than a half turn either way off this you have jetting issues to correct first or an intake leak.

 

I'm new to carbs so what are characteristics of the sound when the engine gets fat(too much fuel)? I'm able to turn the idle mixture screw in and get the bike to stumble at about 1.25 turns to just shy of 1.5 turns. Turning the idle mixture screw out I can get the engine to speed up at 1.75 but the rpm won't fall off till about 2 turns out. This is all adjusted with the accelerator pump closed off by the way. After adjust fuel mixture I get carb pops.

 

You have it wrong. Clockwise is lean due to restricting the flow of fuel, ccw is rich due to more fuel allowed past needle. That being said, the best way to tune it is to find the middle of the sweet spot. When you find the sweet spot (highest rpm at idle with engine warm), slowly turn the needle one direction until rpms drop slightly and note position. Then turn opposite direction slowly until the rpms come back up and then drop slightly again. Note this position, and set it right in the middle of the noted positions.

 

That's what I noted in the original post. So the audible change in sound when going rich is the rpm rise then a stumble. The stumble on both ends are what I want to listen for, then get the middle? Thanks for answering my questions!

 

Get the accelerator pump dialed back in, S&S's web site has the turning manual online to explain it. This carb is designed to have that circuit working or it will pop. I'd set it at 1.5 and go to 11:00 o'clock to the rich side and leave it. I'd also get a can of carb cleaner and at an idle give a shot or two at and around the intakes at the head & clamps. Suspect you got an intake leak, common.

 

I'll definitely check for intake leaks at the joints tomorrow when I can run the engine at my condo. I have the accelerator pump closed off for tuning per S&S instructions.

 

Update: So I got some carb cleaner and sprayed around any possible joint but no audible rpm change.

Just for FYI my settings are as follows:

On a smooth roll onto throttle I get great response but my concern is when I blip the throttle really quickly. When I do blip the throttle rapidly the result is a lag in response. Almost like a long burp lol.Is that indicative of a lean condition?

 

What bikes this on ? How big an engine ?

 

Sportster 1200C 01