Pilot Screw Hole Diameter

[olatheracer]

Anyone know the correct diameter of the hole at the bottom of the pilot screw? Looking at a bike that runs rich, jetting is correct, wondering if pilot screw has reamed out orifice.

[DiverRay]

If in doubt, replace the jet! I know on the early carbs you cannot really see the hole, it's that fine(or my eyes are getting that bad!).

[BA80]

Anyone know the correct diameter of the hole at the bottom of the pilot screw? Looking at a bike that runs rich, jetting is correct, wondering if pilot screw has reamed out orifice.

If you are counting turns instead of properly adjusting the idle mixture there's your problem. Counting turns is OK for a base setting to start with but the fact of the matter is every cylinder will be slightly different and evert carburetor will be slightly different.

If it runs rich no matter the adjustment, the carbs are probably dirty or there is something wrong with a float or a float valve.

What year is the bike you're looking at?

[TopCatGr58]

Anyone know the correct diameter of the hole at the bottom of the pilot screw? Looking at a bike that runs rich, jetting is correct, wondering if pilot screw has reamed out orifice.

Like Greg/BA80 said, what year bike/carbs? The 78-79 have a small hole and the pilot SCREW tip is very fine and often gets stuck, then breaks off, and some folks have had to drill out the hole to get the tip out. After that, adjusting it can be a bit tricky because the opening changes size much quicker with very slight amount of turn of the pilot screw vs. one with a smaller hole.

You say the jets are correct?? Are they GENUINE MIKUNI?? The K&L jets may have the same sizing stamped on them, but they are NOT the same, their sizing is different than MIKUNI and are known to run too large/rich vs. the same listed size of Mikuni! IF the jets don't have the double diamond stamp on them, then they are NOT Mikuni, and they need to be changed.

T.C.

[BA80]

You say the jets are correct?? Are they GENUINE MIKUNI?? The K&L jets may have the same sizing stamped on them, but they are NOT the same, their sizing is different than MIKUNI and are known to run too large/rich vs. the same listed size of Mikuni! IF the jets don't have the double diamond stamp on them, then they are NOT Mikuni, and they need to be changed.

T.C.

Good point TC. When I rebuilt my carbs originally it ran EXTREMELY rich and stumbled on acceleration. Put the OEM jets back in and it cleared right up.

I missed that point.

The pilot jets are particularly touchy that way.