accelerator pump issue

[nascar7613]

2006 XL1200L. When taking off from standing start, the bike hesitates then runs fine. I have taken apart & cleaned the carb, put in carb kit and adjusted the air/fuel screw, around 2 1/2 turns out. I noticed when I twist the throttle, the accelerator pump nozzle doesn't squirt fuel right away, I'd say around 1/8 throttle before the fuel squirts out, and it's a strong stream of fuel. I think that's what the problem is, but there is no adjustment. The bike has a high flow air cleaner & thunderheader, otherwise stock. Running a 185 main & 45 pilot, no shims under the needle. Any thoughts would be appreciated.

 

[TQuentin1]

If you are dealing with a Keihin CV-40 carb, then the accelerator pump is very simple. You can get a rebuild kit for it then open up the housing (3 screws) and take a look at what is in there. May be a bunch of crud, or the existing diaphragm may be damaged (wear). Easiest just to rebuild it and then you know it is in good shape. Chase all the ports with Carb cleaner spray to ensure no blockage or restriction.

But you did not mention the slider and its diaphragm above when you were talking about rebuilding your carb. Did you change that out or at least open up the cap to inspect it? Hopefully no one has drilled out the port in the bottom of the slider. That can affect the low end performance of the engine.

Cheers,

TQ

 

[dolt]

Agree with checking the accelerator pump. However, the stumble you are experiencing is occurring at the transition from the idle circuit which is controlled by the A/F screw to the low speed circuit which is controlled by the slow jet and the transfer ports. 2.5 turns may not be providing enough fuel to avoid the stumble but you shouldn't have to go more than 3.5 turns out if the slow jet is the right size. If more than 3.5 turns out is required, the slow jet is too small. I assume that you did not change any jets? The transfer port could be clogged as well. I don't believe the accelerator pump is only activated with a quick twist of the throttle; a slow roll on of the throttle will not activate the accel pump. I would address the idle/low speed circuit first and once that is squared away and the stumble still exists, look at the accel pump.........