450 Fuel Pump

A buddy of mine has a 450 with a lot of idle problems, we think its the fuel pump.  It runs good when choked but wants to die with minimal throttle input and will not idle all that great unless the choke is on.  Carb has been rebuilt by the Yamaha dealer, plug is good ect. It runs great at wide open throttle but really really hard to start and more cold natured than any other rhino i've ever seen.

What are you folks using for a fuel pump or what woudl you recommend.  Factory?  Electric, both, primer bulb?  open to advice, please help.

Thanks
dh

I'd check for vacuum leaks... check the intake boots, seals at the cylinder head, hose clamp on the head side of the carb, and lastly the vacuum line running from the intake to the fuel pump.  

If it runs good at wide open throttle I suspect the fuel pump is working, since it's run by a vacuum.

I have an electric pusher after the factory fuel pump but I'm not using it.  Unless you're running nitro or a craaaaaazy engine mods I don't think you'd need an electric pump.

Oh, obviously check the pilot screw too.  Screw it in all the way, then back it out 2 turns and fool around with it from there.  

Has it ever run good since the carb was rebuilt by Yamaha?

assuming there are no other problems, it might be your idle speed. book says 1450 rpm, which sounds high. try raising it a little. if you get into get into gear grinding when shifting from high to reverse it's set too high.

the idle circuit from the factory is set pretty lean, and the carb has a hard time keeping prime with low vacuum. i run stock carb, fuel pump, air filter, etc.

depending on where you live, make sure you use good fuel with ethanol stabilizer if it sits for a couple of weeks before runs.

valve lash is off when they are hard to start cold

hay bro i had the same problem as you on my 660 while at the beach in ca. i bought a 12v fuel pump at OReily's auto part store, 3 feet of 1/4 fuel line, 2 small hose clamps, aout 10 feet of small gague wire and fuel filter for about $35.00. i left the stock fuel pump on because it acts as a fuel pressure regulator. so i connected my electric pump from the gas tank suction, discharging into the suction of the stock fuel pump. i left the stock fuel pump on because it helps regulate fuel pressure which is very very low into the carb. you can buy a regulator but i did not. i wired up so when i turn my key on, the pump is powered. works great never had an issue with it.