Does anyone know the difference between the OS .45F and the OS .45F-SR?

Couldn't find anything about the .45s, but Iused to have a .25FSR and a .25F ABC. The primary difference between the two was the FSR was ringed.

i have a 60SR and a 61 F-SR and the FSR has a bigger bore carb


maybe its the same thing with the f and the f-sr

Yes, I don't think a .45f exists.

http://www.osengines.com/history/osm...ax-45fsr-h.jpg .45f sr-h

http://www.osengines.com/history/osm...ax-45rsr-m.jpg .45rsr

http://www.osengines.com/history/osm...-max-45fsr.jpg .45f sr

http://www.osengines.com/history/osm...5rsr-m-abc.jpg .45RSR-M ABC

http://www.osengines.com/history/osm...-45fsr-abc.jpg .45f sr ABC

http://www.osengines.com/history/osm...x-46vf-abc.jpg .46vf ABC

http://www.osengines.com/history/osm...46vr-m-abc.jpg .46vr-m-ABC

Does your engine look like any of these?

i have a 45 F-SR the box says 45F-SR abc the engine just has 45-F stamped on it

Mine has the F stamped on it. I have seen others that have SR stamped on them.

I don't have a box or paperwork for reference.

Maybe BAX will chime in?

As I remember it, the F version was ABC, the FSR version was not.


Vince

O.S. made a .45 FSR ringed and a .45 FSR ABC. The "SR" meant it was Schneurle ported. The "F" meant it was front intake. O.S. made other engines that were "RSR" or rear intake engines. The rear exhaust versions were the "VF" and "VR" engines.

Usually, the case had a small "SR" just under the exhaust port. Because the center crankcase was identical in the FSR and RSR models, it would not have an "F" or "R" cast into the case.

There was no engine designated just ".45F". The FSR was sometimes written as "F-SR". The O.S. Max .45 FSR came out in 1978:
http://www.osengines.com/history/ostimeline07.html

Thanks.

Just a minor point there Bax but the original crankcase casting was made for the first Schneurle ported OS which was the pylon/rat racing rear drum valved OS 40SR which probably indicated Schneurle port Rear induction (maybe even Racing). The same crankcase was then used for the Front induction sports engine so the engines were then called FSR although still keeping the SR under the exhaust port. I don't know if the 45FSR kept the SR or whether it was replaced by a 45 under the exhaust.

Bax,your almost completely correct. Only 1 small mishap,that everyone makes. I have the OS complete tare down and manufacturer's labeling for pretty much,every OS engine up to 1991. The Letter's following all the FSR series engines,actually is a acronym for short. The F stands for FOUR,the number of ports in the case. The S is for Schneurle the type of porting. Last but not least is the R,it stands for RINGED only,not rear.

Every FSR engine is a Ringed engine,unless it was modified,which i have seen people do to make the ABC version.

Good lying all Art

Except if it's an ABC like [link=http://www.osengines.com/history/osm640/osm-1980-max-45fsr-abc.jpg]this[/link] one or other FSR's that were ABC/ABN.

Hmmm... The front intake engines all had "F", and the rear intake had "R", as in ".61FSR" and ".61RSR". The front-intake, rear-exhust engine was a "VF", and the rear-intake, rear-exhaust engine was a "VR".

.60 FSR: http://www.osengines.com/history/ostimeline05.html
.60 RSR: http://www.osengines.com/history/ostimeline06.html

.61 VF and VR engines: http://www.osengines.com/history/ostimeline07.html

The airplane VR is here: http://www.osengines.com/history/ostimeline09.html it came out later than the marine versions.

Incredible, OS had a rotary engine back in 1970.

There's some history behind this (and I may not have it completely correct because I'm going from memory ). Graupner in Germany were awarded the license to build small Wankel engines (up to about 100cc IIRC) but didn't have the necessary machinery to make them so asked OS if they would make them. OS didn't have the machinery either but they invested in modern CNC which was the only way to make the epitrochoidal cylinder. The Wankels were sold as Graupner OS (or OS Graupner, whatever ). The big deal about all this was that OS now had CNC machinery which was perfect for mass producing normal 2 stroke engines (which obviously sell in much larger quantities than the Wankel) so they did a total redesign from anything they'd made before and came up with the 40SR pylon engine which soon morphed into the FSR.

So, I have just come into ownership of a "45F" (Stamped under exhaust). This is a ringed version; I already have two ABC(N) versions,

I always thought these were fitted with a standard type ring. This one has a Dykes type ring.

Can anyone enlighten me?

Thanks,

DF