Exploded View of Older Pump?
 

I may be getting stuck with an OS 120 surpass with pump. The first version that is out of production.
The pump is not working properly and I may end up taking it apart. Before I do it sure would be nice to see an exploded view of the pump so I know what I'm gettting into.

Thanks,
Jeff

Exploded View of Older Pump?
 

Jeff,

We're sorry, but we don't have an exploded view of the old pump from the original FS-120 Surpass engine. That pump was never repaired outside of the factory. It is made of several machined layers that are separated by glued seals. Opening the pump usually rendered it useless.

Pumps were replaced here and repaired by the factory. Unfortunately, O.S. no longer supports that pump because it's been out of production for so long.

Exploded View of Older Pump?
 

OK.
What does the large brass screw in the center do?
While the in and return fuel fittings move absolutely no fuel and no amount of pressure will push fuel or air through them, the out fitting to the carb does move air.
I'm fairly adept at taking things apart and putting them back together in working order.
I just don't know what is inside this thing.
Any help would be appreciated.

Thanks,
Jeff

Exploded View of Older Pump?
 

Jeff,

The large brass screw adjusts the regulator diaphragm. It's supposed to be adjusted so that the engine is running at peak RPM with the high-speed needle at one turn out.

The return line will open only when the engine's running at low throttle and the pump is moving fuel. A spring on a check valve keeps it closed otherwise.

Usually, fuel will move through the pump only when it's turning. You can't really blow through it and expect any results.