Wheeler ran real good but started leaking at the bottom of carb so I pulled carb off and cleaned(all looked clean to start with)and replaced
just the needle and seat with a new oem pair. now the wheeler doesn't leak gas but sputters
a bit and has low power and I didn't change anything else nor did I make any other adjustments. When I turn the fuel off while driving it cleans right up and power comes back til just runs out of gas.
Could any one please help? Really appreciate it. Thanks.

 

Would help to know what year model as they had a Bst34 and Bst40 carb depending on year model. Before 2000 used the 34mm carb and the float level set at 0.51 with the carb turned sideways and float arm barely touching the float needle. Bst40 adjusts basically the same way except the float lines up with the carb body.Sounds like fuel level too high which may be your problem especially when you turn the fuel off, as the fuel level drops it runs better.If you have a 2000 model or later here's basically the same carb on a Ktm.The BST-40 Bible - ADVrider
Plus here's how the bst 40 should look like when float is adjusted right.

 

Sorry,it's a 1999 SP 500 and sure appreciate your help. It ran fine b4 I changed the needle and seat,it just was leaking gas. Now it doesn't leak but just doesn't have the power. One thing weird is ever since I've owned this machine it's been a super great starter without ever needing to use the choke whatsoever at temps even below zero. Carb ID is Mikuni 50l09b E965. Hope it's original to machine.

 

It's the bst34 carb and some things on this model that people over look is the float assy itself and the float pin as they don't come in any carb kit along with a new o-ring for the needle and seat if you didn't install one.If the float pin is worn and wobbly,the float can stick allowing too much fuel. Plus you adjust this carb the same way,just turn on its side until the float tab just touches the needle. Should be 13 mm (.51 inches) from the top of the float to the carb body. Bend the float tab up or down slightly if necessary to set the float level correct. Dirt Cheap Yamaha, Honda, Arctic Cat & Polaris OEM Parts & Accessories – Cycle Parts Warehouse Plus check simple things like the diaphragm and slide is ok along with the spring and slide needle. Should be able to lift the slide and should snap back down easily.

 

Old Polaris Tech, I pulled the carb back apart and noticed the spring in diaphragm was just laying in there instead of on it's post so I reinstalled it,diaphragm looked good and it does spring back(not real fast but does?.Yep,I did replace the oring on the new needle and seat. Been running it and it's much better but still has a hesitation/stumble at wot right out of the gate and stumbles a bit/lays down a bit at times in low range. When I turn the gas off is seems to clean up as b4 so still seems like it's running a pinch too rich still. Basically It acts just like it did before but not near as bad since I put the diaphragm spring back where it belongs. It's tolerable but the hesitation out of the hole is annoying. I do notice just a pinch of gas hanging around in the overflow bowl tube. Not enuff to drip but I see it there after I test drive. Thanks again!

 

In that case just bend the float tab down just a little so the fuel level in the bowl drops and see if that solves the problem.If it doesn't help,it could be something other than a carb on the hesitation such as belt or clutches.

 

Ok,thanks. I'll check the float. Could the float have changed in time/If the spec is right on .51 should I still change it or is it possible it's getting too heavy? I couldn't find a weight spec. Would changing the needle e-clip height lean it out a pinch? Do you recommend changing the spring in the diaphragm or don't you think that would help. I've heard of that helping out for hesitation/bog-sputter. Or maybe complete carb kit(although never very complete)?Thanks again for helping me and so many others on the ATV connection. Much appreciated!

 

There's no float weight specs,but yes over time float height can change because of wear and vibration. You can drop the needle clip(raises the needle) which richens up mid range and see if it helps. If it makes it worse go the other way. Could be as simple as that could solve the hesitation. I wouldn't replace or cut the spring as I've heard that some have done.

 

Problem fixed and may thanks/and blessings to you Old Polaris Tech!! Float must have been out of adjustment from years of use just like you said. Adjusted the tab needle rides on to be parallel with bowl surface and hesitation-sputtering gone!

 

Simple thing to overlook,but necessary for em to run right.. Glad you solved the problem.