09-07-21, 03:26 PM
Most likely the Float valve O-Rings, however there is no need to buy a kit as removing the O-ring is usually easy enough and the quality of the original need valve and seat is usually much better than non Mikuni replacements.
You need to get 7.5mm ID X 1.5mm CS (cross section) x 10.5 OD FKM/FPM 70 or 80 O rings Asking for Viton is the same but the FKMFPM is more specific. I have changed many of these over the years and only once have I had to replace the Valve seats and that was on a 1974 Honda 4
With the carbs off and the float bowl removed, Remove the Float and needle then remove the Float valve retaining screw. Spray around the edge of the float valve with wd40 and allow it soak for a while.Tape the jaws (duct tape is best) of a pliers . Lightly grip the valve and twist the valve half a turn. if it twists then pull it out gently. If not apply more WD40 and leave it soak for an hour.Prise off the O-ring taking care not to damage the o-ring seat. Do not mix up the seats as you will reduce any float height issues later. I use a small pick or a very small jewellers screwdriver. Spray the seat and new O-ring with WD40 and prise the O ring on with your fingers.
Spray the Carburettor Valve seat with WD40 and push the Valve back in. Screw in the locking Screw.
Continue with the other 3 and reassemble the carbs.
If you undo the Main Jet you may as well replace the O Ring there also and that is a 5.5mm ID x 1.5mm cross section x 8.5mm OD also FKM/FPM 70 or 80
You need to get 7.5mm ID X 1.5mm CS (cross section) x 10.5 OD FKM/FPM 70 or 80 O rings Asking for Viton is the same but the FKMFPM is more specific. I have changed many of these over the years and only once have I had to replace the Valve seats and that was on a 1974 Honda 4
With the carbs off and the float bowl removed, Remove the Float and needle then remove the Float valve retaining screw. Spray around the edge of the float valve with wd40 and allow it soak for a while.Tape the jaws (duct tape is best) of a pliers . Lightly grip the valve and twist the valve half a turn. if it twists then pull it out gently. If not apply more WD40 and leave it soak for an hour.Prise off the O-ring taking care not to damage the o-ring seat. Do not mix up the seats as you will reduce any float height issues later. I use a small pick or a very small jewellers screwdriver. Spray the seat and new O-ring with WD40 and prise the O ring on with your fingers.
Spray the Carburettor Valve seat with WD40 and push the Valve back in. Screw in the locking Screw.
Continue with the other 3 and reassemble the carbs.
If you undo the Main Jet you may as well replace the O Ring there also and that is a 5.5mm ID x 1.5mm cross section x 8.5mm OD also FKM/FPM 70 or 80