Automatic Project

Oil Mixer Addition


After a little research I found that the oil mixer device on the PK50 and PK 80 Automatica was similar to the one on the PK 125 Automatica. Also it seemed that all the casings were cast the same regardless of whether they had an oil mixer system or not.

The wheel side of the crankcase has a small bearing cover on the non-mixer model, but has all the holes for a mixer device. I found the carb also has the linkage in place to accept the mixer device.

I removed the cap by removing the three retaining bolts to expose the end of the crank. It turns out that the only difference between a non mixer engine and a mixer engine other than the system itself is that the crank nut is different and incorporates a drive gear..

Above shows the special nut that drives the mixer device from the parts manual.

To remove the nut I locked the crank with a con rod holding tool, and then loosened the nut..

With the nut removed I could start searching for a mixer device. I found the best place to look was the German eBay site. Ralf at SIP Scootershop was very helpful and offered to allow me to use their address for sellers that weren't willing to ship outside of Germany. Now if I can just find one - more to come soon.

I managed to score an oil mixer device from a PK 50 Automatica, which looks the same from the outside, but I am concerned it moves less oil due to the original bike being a 50cc. Since it will now go on a 125cc I may have to modify it so it pumps significantly more oil. Looking at the part there is a throttle arm connected to the carb (green arrow), a drive from the end of the crank (blue arrow), and a small tunnel where the oil is pumped out (red arrow). The long tube is the oil intake from the tank.

I have taken apart the whole engine since the previous shots so the crankcase half is no off the motor and cleaned up. I found that non-oil metered bikes have no hole drilled through to the intake area for the oil to mix with the gasoline/air mixture.

Only one thing to do! I found a drill bit the same size as the hole out of the oil pump, figured out where it needed to be drilled, and then drilled straight through the casing half.

A test fit on the bare casing shows how the mixer integrates with the casing half. I might need to trim the intake tube depending on what happens inside the small frame engine bay.

One more modification that needed to be made to the crankcase half was to srill a larger hole to allow the linkage from the trottle to operate the throttle arm of the oil mixer. The arm passes through the space just under the carb intake shown with an arrow above.

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