Quote:
Originally Posted by Alollo Dean
Another question, how in heck do you get to the idle screw? That is it on the right side right behind the frame?
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Tbolt USA has these knob type adjustors:
https://tboltusa.com/store/tusk-fuel...k-p-10604.html
They sell a fancier adjustor for $35 or so that lets you adjust more easily. But the small knob style works fine, you just have to turn the knob with a screw driver end.
https://tboltusa.com/store/flex-jet-p-1063.html
Also can get the knob type on Amazon for $8...free shipping.
https://www.amazon.com/your-orders/p...ntId=DkVqqkG2d
This is for a Mikuni VM26-flange mount (like on most 250 China bikes).
Turn the Pilot Jet Screw "in" (CW) till it just stops. Turn 1-1/4 turn "out" on the screw, then turn out (or in) 1/4 turn increments. Have someone with you to keep the bike running while you turn the jet out (or in). Turning "out" (CCW) increases your fuel into the Pilot Jet since this is on the engine side of the carb (if the Pilot screw is on the intake side, as with other carbs such as the VM26-606, then turning out increases air). Do this until you get a good idle.
If you get past 2 turns out, then you should consider a larger Pilot Jet. If you have to turn "in" (CW) to make more lean (under 1 turn) then you need a smaller Pilot Jet. Order a couple jets (either larger or smaller depending on what you find)..I had to go from a 20 stock to a 30 to get mine to idle at 1-1/4 turns, 1500 rpm.
Once you get idle, then run at mid-throttle for a few miles (5-10) without stopping (much). Check your plug. Decide if rich (black) or lean (white). If tan, then OK. If black, then move the needle clip up one notch to lean out. If white, then move needle clip down one notch to richen. Do the spark plug check again. Look for Tan.
Find somewhere you can run full out for 10 miles. Pull over, remove spark plug. (I didn't shut the engine off at speed and coast to a stop like some folks say...I just needed to be close enough and I don't think going to idle for 30 seconds will change the plug much) Black/Tan/white? Go up or down one Main depending on color. Because I am at a Mile High, I ended up with the 100 Main that was stock (would likely be lean at sea level).
This process worked for me on my RXB150, that came with the "real" Mikuni. Tan plug all the time.
Jetsrus.com: Mains: Mikuni N100.604 (Jetsrus # M21), Pilot: Mikuni VM28/486 (Jetsrus # M24). I get my jets from them in 2 days. They are about $5 each for the aftermarket type and $7 for the genuine Mikuni.
Followed the same procedure when I put a VM26-606 on the TT250. I am down to where I am going to try one Main larger, as I got tan, but still a bit too white I think. I thought with this carb I would avoid the problem of the Pilot Jet Screw location (as with the PWK28 I was replacing it was accessible), but it ends up being the frame. Luckily, with a spigot mount carb it isn't a big deal (time wise) to remove the carb and tweak.