Sunday, June 21, 2015

Carburetor woes, or How to not kill yourself on a Mikuni Part 2

The last post had a lot of specifications and some details. So now I am going to use all that information to figure out what i am dealing with on the Pegaso.

Main jet 107.5(or 110)
This is good. A number that both makes sense and is definitely doable

Idle Mixing Jet 17.5
Here is where things don't make sense. More research and reading shows that this is actually correct- it simply is not referring to the pilot jet like I had thought; there is an actual idle mix jet under the diaphragm!


Needle 5E76-2
Another good. My carbs have this needle in them! yay.

Air Screw 2 turns
When I took the carbs apart they had the air screw out about 3 1/2 turns. This didn't make much sense to me but i had read in the "social wisdom" about people suggesting such settings.

Float Height ??
Amazingly I could not locate a specification for this in the manual!
The BST Bible on ADV Rider says float is set by aligning the seam on the float with the base of the carb. GSTwins says float height is 14.6mm, which appears to agree with the Bible thread. BMW funduro appears to say 14.6mm float height. Suzuki DR manual says 14.7mm


So with all of this information I seem to have the basics for setting up a good baseline carb, with two three exceptions: Idle jet size, and needle clip position, and accurate turns on air screw.

According to user andysrage on apriliaforums.com the factory idle jet is a 37.5, with 4.5(!?!?) turns out on the idle air screw.

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