what engine is this?

LAST EDITED ON Apr-29-04 AT 05:49 PM (CDT)
 
My first OS engine and not sure exactly what model it is. The seller said it was a FP, but this has ball bearings.

Thank You

It's a steel sleeve .25

OS .25F. It could have made sense if they'd called it an FSR. Maybe FSR wouldn't fit on the smaller case? Steve

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Looks like a 25 SF case. Dennis

Some engines exactly like the one pictured came in boxes with "FSR" as the model name. The "fluted" style bypass was seen on the early iron and steel FP's and the first of the 21, 25, & 28 FSR's. At about the same time that the FP's changed from iron to aluminum pistons, the FP case style was modified, with a fillet to fill the side of that flute shape.

The smaller FSR's kept the same case when they were available in true ABC (and the box was labelled 25-F ABC), and beyond that, when they were ABN. The next model of the BB shaft OS Max 25's was the SF, when the filleted bypass first appeared on these engines. That was also about when the 28-F's were replaced by 32-F's, and for some reason the SF's had a shorter production run than the FSR's/F's, being replaced in their own turn by the FX's.

.

Kiwi