My 2001 883 sportster starts fine and idles fine but when I turn the throttle it sputters. I have had the carb rebuilt changed the spark plugs and this still happens, please help.
Your issue sounds like a carb /intake issue to me. There is some chance that it is low high voltage spark output, but typically you would have other complaints.
So, how well is it idling? check for tight intake to head seals, big problem area. Squirt some water over the joints, and if the idle changes, something is leaking.
You did not mention if the sled eventually speeds up, so I am going to guess that it might do so, eventually.
AREAS that need inspection is the accelerator pump. This is sometimes a misleading area in that it can appear to function, but not be correct. This system has an inlet valve and an outlet valve, normally little steel ball bearings. IF an output valve leaks, you will not be "primed" and the first twist will only fill the discharge port, and not actually discharge. BUT if you sit there twisting the throttle, usually the pump will discharge a visual squirt. (this squirt sometimes needs to be aimed correctly, center of the air flow stream.)
Another are is the off idle circuit. This circuit requires correct float level to work. It gets clogged easily. You mentioned that the carb was rebuilt. It is critical to blow HIGH air pressure through the passageways AFTER soaking in carb cleaner for a while. (You can also clear this circuit, sometimes, by air cleaner off, reving the bike, give wider throttle and place your hand over the carb inlet, closing off 100%, for a brief moment. Bonzai, for sure, but works more often than not. almost always works on lawn mowers.)
Since you are not certain as to whether this is an ignition or carb/intake issue, you can also try artificial enrichment. I use a propane torch, with the discharge orifice removed, and a long rubber hose slid over the tube of the torch. you can add fuel directly in the carb throat and get results. this can help narrow down what is happening.
Best to you, and I hope these ideas help you zero in on what is happing on your sled.
on Oct 06, 2014