Mikuni vm28 carb from 80's and 90's yz80

[deeeebeeeeee]

These carbs are an exact fit to the intake and air filter boots.
Have a quick jet change carb bowl on it.
Requires a non tors throttle cable.
Can use the stock blaster slide.
Has the idle screw mounted on the side.
Comes with a #35 pilot jet.
Can be found on ebay for less than $20
For all the reasons above I feel the vm28 yz80 carb is the ideal upgrade for the stock carb even on a stock motor it will help top end, without harming the bottom much.
It can also better support piped motors and mildly built motors.
Tuning is way easier than on a stock carb.


It uses a 332/249 needle jet which is yamaha oem and only available in certain sizes. The 92 yz80 has a Q-2 jet which i believe will suit our purposes. The 85 version has an O-0 Needle Jet which is a bit small for our purposes, other sizes may be available as oem yamaha in various years.

 

[Fast6hand]

Do the jets fit as well?

 

[deeeebeeeeee]

It uses all the same needles and jets except for the needle jet which as stated above is oem Yamaha

I also wanted to note that it is easier or more like fast er to tune simply because you can change needles, clip settings, main jets , or even needle jets all without removing the carb, fuel tank, or carb bowl.

The 92 version has a larger fuel inlet, dual vents, and a two position choke like stock except for the larger fuel inlet. The older version had a single vent ,single position choke, smaller O-0 NJet, and standard fuel inlet.

 

[deeeebeeeeee]

I read a post today were someone had went up 2 jet sizes from stock to a 250 main jet with a vm30 carb.
So I makes sense that a vm 28 would take one size over the 26.
I am going to use this to figure my baseline and go from there.
Based on a Toomey pipe nd u I filter with no airbox lid I believe ends up around 310. So figuring I should end up around 320. I will Start a little fatter at say 340.
Will report back with results.