Topic: 73 cb 500 FOUR wont idle without choke

[zoombyu]

i can start the bike with the choke on but it wants to idle VERY high. So i backed out my idler screw until i could slowly dial out the choke. This works fine until an millimeter before the choke if off. the second the choke comes off, the bike just dies! no matter how much throttle you give it, it stalls out like its staving for fuel or something.

Mind you, i bought the bike a week ago, rode it all around and changed the oil and plugs and my dad started it up after and he said he only adjusted the idle to get it up to 1200 and then it just crapped out from there and we couldnt get it to idle after that. put old plugs back and checked for spark and all four look good. took my carbs out to see if gunked up and they look like the previous owner took them off yesterday and cleaned them. Im completely lost!

A few times while having the choke on, it has wandered up and spiked to about 5k rpms and fluctuated between 1500-3k rpms and back down. has a ghost inside! haha. any input would be greatly appreciated.

[dave500]

its an unknown bike youve just bought that is at least running,start by going right over the ignition,plug cap resistance and all,,then set the valves and adjust the cam chain,,then futz with the carbs and decide how many times you want to pull them off and clean them,if you take them apart clean them once but well.

[Chachi]

Everything Dave said... but also... How much fuel is in the tank? How bad is the inside of the tank? Are there inline fuel filters? Is the petcock bowl/strainer clean? If all of the basic fuel needs are normal with no obvious obstructions, how long are you letting it warm up before you set idle? My 500 is kind of cold natured. I typically have to start with choke, but then with throttle I can keep it going while I ride off and it's good to go after a few minutes (and I never have to adjust my idle screw). Do you still have the the throttle lock installed? If so, you can warm it up with that on for a few minutes and get the idle screw set once it's warm (RPMs at a 1,000). And since it's new to you, it may be worth it to drain the tank and remove the petcock to make sure the stand-pipe is in there and in good order - mine was not when I got my 500.

[zoombyu]

I recently added some more fuel to the tank and the tank looks clean. previous owner lined the tank with something. seems to be getting fuel just fine, ill pull the petcock and check it. The bike is for sure getting warm. I rode it for a week and it idled just fine without the choke after warm. it wasnt until I changed oil and plugs that it started doing this. ALso, if i put the choke on all he way, the id;e wants to go way up to 5k. is there any way to set what is idles when choked  or is that automatic? I'm able to idle it with the choke just barely on, but that last millimeter from choke "on" to "off" kills it when off completely. it'll rev just fine and the second you turn the choke off, it seems like its starving for fuel or air even if you rev it up and then dies out.