Difference between OS MAX FP & FSR ?

Hi Guys,

I have two OS MAX Engines, a .10 FP and .10 FSR-S,
I looked at the OS MAX website and tried to find
literature but came up empty.
Is the FSR a Schnuerle ported engine like the FP ?
I believe the FP is a ABN? Is the FSR steel or ABN?
just curious.

Thanks,

LAST EDITED ON Jan-18-04 AT 00:28 AM (CDT)
 
In general, FP engines were plain bearing, FSR were twin ball bearing. But I don't know about the .10s. The .25FSRs I have (two) have lapped steel piston/liners. No guarantee they're all like that, of course - they made them over a long time. The trademark characteristic of these two series is that the cylinder ports are rotated 45 degrees, so they're really somewhere between a side exhaust and a rear exhaust, except that the muffler lugs are set up to take a side muffler.

I see what you are saying Iskandar, about the exhaust ports
both the FP and FSR are like that. I also know by the use of
a magnet that the FSR is lapped-steel running in a steel cylinder.
So that rules out ABN. I looked at the OS Max website again and noticed
the .25 FSR and the ball bearing housing, my little FSR is not ball bearing.
Now I need to find out if the FSR is a Schnuerle ported engine.
Thanks Isky, your answer provided impetus to put on my thinking cap.

>Now I need to find out if the FSR is a Schnuerle ported
>engine.

I have a 10FSR I purchased late 70's, pulled out the instruction sheet and here is the first sentence :
'The new MAX-10FSR engine incorporates a schnuerle scavenging system and is the first small size O.S. motor to do so.'

There's also an addendum sheet explaining two different liners used in the 10FSR - not interchangeable - May '77 being the change date. Two different crankcases for the 10FSR, both plain bearing.

Man! I've had that engine for 27 years, where'd the time go! I first used the .10 on an RC job, now it's on a Buster with the throttle wired open, must have 500 flights on that plane, great roundy-round trainer for the kids, engine still runs great.

Steve ..

The FP engine series started life as iron piston and went to ABN. The ABN were more tolerant of the lower oil content of much of the RC fuel being used, but I still liked the iron piston versions best. And they were lighter, too. Either should be adaptable to our purposes, and, yes, they were both Schnurle ported (and very similar, if not identically so.)

I was not aware that the FP's started out as iron pistons.
Always interesting stuff one finds here.

Thanks.