Quote:
Originally Posted by jayr
So keep the 42 pilot jet? To check the valve clearance, just line up the T mark with the line in the peak hole. And check for 0.05mm?
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Going up from a 40 to a 42 is similar to my going from a 25 to a 27.5 on my Mikuni clone. If 1 1/2 turns works well on the 40, then likely you will need to go in on the mixture screw and might be closer to 1 turn out. This is just a general rule of thumb. Was the 40 giving indications that it was too lean?
If the Keihin Jets are true to size then you can still use peoples Mikuni setups to help get a good starting point for your carburetor.
Here are a few Mikuni (M) and equivalent Keihin (K) jet sizes.
100 M - 110 K
102.5 M - 115 K
105 M - 118 K
107.5 M - 120 K
110 M - 125 K
112.5 M - 128 K
115 M - 130 K
117.5 M - 135 K
120 M - 138 K
122.5 M - 140 K
125 M - 145 K
Keep in mind that this ONLY applies to genuine or high quality aftermarket jets. I am under the suspicion that many Chinese made jets don't follow the same sizing standards, but I could be wrong. I always recommend genuine jets if at all possible.
One advantage of the Keihin jet system is that it covers a few inbetween sizes that the Mikuni jets do not if you really wanted to get in there and super fine tune the carburetor. An example of this is the step between a 115 and 117.5 Mikuni jet, aka a 130 and 135 Keihin jet, you will find a 132 Keihin jet size that has no mikuni equivalent - which I guess you could call a 116.25 if it existed.