Carby Mikuni VM-20 Idle absolutely sucks!

Tony the Wrench

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So, a long run down...I have a Smolik billet vertical block, MXS sport cylinder, Smolik billet head, 47.6mm bore × 43mm stroke, Mikuni VM-20 w/250 main & stock 22.5 pilot. KTM ignition, NGK BR8HS plug, Stage 6 street race expansion chamber & stinger silencer. This thing RIPS with 10/36 gears and pulls the front wheel @ 50mph.
Idle absolutely sucks! Inconsistent, only idles high. Air screw does very little. You can make it stall turning in to 1 turn or make it rise at 2 turns out (screaming) because of the already high idle befor but if you try to lower it , it dies. After a blast around the neighborhood it'll just die & lucky if it'll fire up again. These carbs are SO picky. 250 main? YES & with a great plug read.
Somewhere around 13k rpm and not kidding. RDM crank, balanced rod (big end/small end), real bearings (USA) & even ARP hardware. The MXS cylinder & piston I believe are out of the 📦 parts so... I say that because a radically ported eng tends to require a higher idle. I'm stumped.
 
So, a long run down...I have a Smolik billet vertical block, MXS sport cylinder, Smolik billet head, 47.6mm bore × 43mm stroke, Mikuni VM-20 w/250 main & stock 22.5 pilot. KTM ignition, NGK BR8HS plug, Stage 6 street race expansion chamber & stinger silencer. This thing RIPS with 10/36 gears and pulls the front wheel @ 50mph.
Idle absolutely sucks! Inconsistent, only idles high. Air screw does very little. You can make it stall turning in to 1 turn or make it rise at 2 turns out (screaming) because of the already high idle befor but if you try to lower it , it dies. After a blast around the neighborhood it'll just die & lucky if it'll fire up again. These carbs are SO picky. 250 main? YES & with a great plug read.
Somewhere around 13k rpm and not kidding. RDM crank, balanced rod (big end/small end), real bearings (USA) & even ARP hardware. The MXS cylinder & piston I believe are out of the 📦 parts so... I say that because a radically ported eng tends to require a higher idle. I'm stumped.
Sounds like an expensive set up. How much does it cost for all that stuff if you don't mind.
 
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