What is a good carb set up on a 2005 yz125 with new motor hot rod crank and wiesco piston all stock specs. I have a 45 pilot jet now with std main jet. Took out the 40 pilot jet because of breaking up at low cruising speeds.

check the timing setting as it may be too far advanced ( set at 5 degrees advanced to start) check and adjust the fuel setting of the main jet as it may be too rich at idle.. You state that the flywheel was out of true and with the vibrations I suspect that the crank shaft may be bent. Something that would not normally be checked

Here is specs for those carbs
- AISAN AS27VW
I.D. No. - 04A10
Bore - 27 mm
Idle r/min - 1300+/-100 r/min.
Fuel level - 9.0+/-0.5 mm
Float height - 20.5+/-1.0 mm
Main jet - #94
Main air jet - 1.2 mm
Jet needle - 5B10-3rd
Needle jet - 2.60 mm
Throtlle valve - 11.0
Pilot jet - #34
By-pass - 0.8,0.8,0.8 mm
Pilot outlet - 10.8 mm
Valve seat - 2.5 mm
Starter jet - GS1 #60, GS2 #54
Pilot screw - PRE-SET (2 turn out)
Pilot air jet - 1.35 mm
Throttle cable play - 0.5 - 1.0 mm
Choke cable play - 0.5 - 1.0 mm

all thats been set at the factory--only thing can ajust is idle speed--the jets or float level may hav issues and the magneto cud be weak at kick

Stock it would be around 2 turns out.

These bikes shipped with only one jet needle (unlike other Yamaha's) the bike's factory jetting is 45 pilot, NBKF needle on the 2nd clip from the top, and 138 main. This bike tends to run a little rich off the bottom, so I'd recommend running a 42 pilot instead. When it's really hot out (over 90) you can run the 135 main jet.

Screwwing with carbs is fact of life with these bikes - you will have to do some tweaking no matter what.

i put 115 main jets in my 77 ge 750 and it will run but was told to jump up to 140 with pobs and 4into1 pipe (SM6) race pipe at the low side run 130 main and leave the stock pilot in. i rorde mine from NE to SD roude trip about 1300 miles got about 62 MPG with 115 jets jumping up to the 140 will drop the MPG but lets be real im not looking for MPG. hope this will help.

the us bikes are normaly set up to meet the california clean air regulations, as europe have/had no restrictions i would expect the would be jetting differences, prob on the lean side of things for the us bike larger main jet etc, if you find a carb check and see what jets are fitted for main and pilot, also the needle might be set lower..( weaker )

Stock Jetting for a 1994YZ250 is:

350 main
45 pilot
J8-6EJ33-61 needle

Adjust your jetting down one size for each 1000' of elevation above sea level. Needle clip position on the needle fine tunes the pilot circuit.

Scott

The stock main jet is 127.5. The stock pilot jet is 32.5 The stock jet needle is 0-8. The sizing on the needle refers to the taper in diameter.

Causes of flooding on your bike are:

1. Float level set too high
2. Too large a main jet, #420 std. ( 400 min, 470 max)
3. restricted air flow / filter
4. Pilot jet too large #40 std. (35 min, 45 max)
5. Air screw set too lean
6. Jet needle clip set too low on the needle

If you are not running an open or free flowing exhaust go back to the stock size jets but use the DynoJet parts instead of the stock.
DJ jets tend to run bigger than oem jets