77 500 xs: tried siliconing the intake mani's with no such luck. The bike idles great and has awesome throttle response when cold (no backfiring too) but as soon as she warms up I'll get the infamous high-idle and awfull low-end throttle response; also starts popping. I do have cracked and dry-rotted intake mani's. Will 650 Mikuni BS38 carb boots off of Mikesxs.com fit my Mikuni BS34's? I do believe mine are 38mm (not sure) diameter openings. If they will not does anyone else know of a reference or site I could get some new ones from? Thanks.

mikesxs.net sells boots for both 38s and 34s.

also cross reference your bike with the part numbers on the xs650 to see if they use the same parts.

Yamaha part numbers can be found here

http://www.yamaha-motor.com/sport/myyamaha.../starthere.aspx

Thanks a lot!! A response finally!!

77 500 xs: tried siliconing the intake mani's with no such luck. The bike idles great and has awesome throttle response when cold (no backfiring too) but as soon as she warms up I'll get the infamous high-idle and awfull low-end throttle response; also starts popping. I do have cracked and dry-rotted intake mani's. Will 650 Mikuni BS38 carb boots off of Mikesxs.com fit my Mikuni BS34's? I do believe mine are 38mm (not sure) diameter openings. If they will not does anyone else know of a reference or site I could get some new ones from? Thanks.

Sound like you might have a clogged pilot circuit.. It's often mistaken for a vac leak..

Have you tried cleaning the carbs? Pilot jets are under the brass screw in caps next to the main jets.

That passage leads to the pilot screws and then to 3 tiny holes on the roof of the throttle bore on either side of the throttle blade.

clean em all out really well.

Sometimes the pilot jets are stuck and you have to easy-out em and replace.