Hey guys,

Just wondering whats the difference between the OS FS-70 Ultimate and the OS FL-70. All I can see is the price

Cheers

gosk8ing,
Ok, here are the differences between the two engines. The FS-70 has ball bearings in it where the FL-70 has bushings. The FS-70 has a low speed needle valve where the FL-70 has an air bleed low speed adjustment. And finally the FS-70 has a metal backplate and the FL-70 has a plastic backplate.

Of all of these differences I would say the biggest of them is the low speed adjustment. IMHO an air bleed low speed adjustment is about the most worthless thing on an airplane engine. They are very hard to make minor adjustments and very frustrating. I fly almost all OS engines and I have had exactly one air bleed adjustment, and will never have another one. Period. If you want my opinion spend a little extra and get the FS-70.

Hope this helps

Ken

They are two totally different designs. The "Ultimate" 70 has not enjoyed the reputation earned by it's Surpass 1 & 2 counterparts.

The FS-70 is not much more expensive than the FL-70, and is a proven winner. It gets my vote.

Well from someone who didn't know better I bought the FL-70.It was my first 4 stroke engine.I followed the manufactors break in and operating instructions and have never had a problem.It has several gallons of 15% Cool Power through it now and still cranks out plenty of power for a 40 sized plane.Maybe I got an exceptional one?I'd buy another.

Say what??????

I've got an OS FL-70. I just went to the shop and pulled out the Owner's Manual to verify a couple of things. I couldn't believe what I just read and figured I had to have gotten a couple of things horribly wrong when I bought my FL-70.

The sucker has two very robust looking ball bearings. Honest. The case certainly has bulges where they'd be, and the manual has parts numbers for them.

As for the primary differences between the FL and the Ultimate and the Surpass, I'd have to say that there are a couple. And what I've seen and read, they are in conflict with what's just been posted here. But hey, check out Tower's online catalog. It's often the last word.

The FL costs $180 and the Surpass costs $210 and the Ultimate is $300. That's $30 difference to the Surpass and $120 difference to the Ultimate. A friend just bought a MagnumFS, and Magnum is a lower cost mfg, right? Well, the Magnum 70FS and the OS FL-70 were both selling for $180 last week.

The Surpass is appreciably heavier than the FL. They advertise the FL as being a lot lighter. It is. The Surpass is 22.1oz with muffler (anybody fly one without a muffler?) and the FL-70 is only 18.3oz with muffler. I bought the FL-70 because it's about the weight of the OS46AX (two stroke). The Ultimate is actually lighter than the FL by about as much as the 46AX is. If the Ultimate wasn't $120 more than the FL, I'd have bought it instead of the FL. But so far, the FL has shown no faults and seems to be a typical OS, excellent.

To sum up the difference:
FL costs $120 less than Ultimate
air bleed vs LS needle
Tower says Ultimate is unavailable

BTW, I just tried to find out if the Ultimate is ringed or ABC or what, and couldn't find out. That might be one reason for the difference in cost.

Boy, this is interesting...............

In trying to find out if the Ultimate is ringed...............

They list a ring in the parts list. But it's described as the ring for a .91FX. Honest! And the wrist pin is also described as for the .91FX. Since they also describe the engine as "very compact", I would assume that the sucker is what one could call "overbored". It appears to be a short stroke, "bored out" design.

very interesting

Darock,
I do stand corrected. You are correct and I made a mistake about the bearings in this motor. I was thinking of the LA motor when I typed that. I apologize if I created any confusion for anyone reading this.

Ken

If I understand what I read, the difference in the 2 are the rings in the piston on the FS, and the FL is sleeved.
[X(]Oops![X(]and the carb low end adjustment!

chuckle.... chuckle.....

You are almost always right so when I read that I almost fell out of this chair. I was getting ready to kick myself for paying that much for a plain bearing engine, but mostly for somehow not noticing the fact. and then........ to top that off............ you don't like airbleed........ man, what's wrong with me!!!!

Truth is, I've not ever had any problem with airbleed. That's really what I "grew up" with. I've got a couple of students flying plain bearing, airbleed OS40s and them suckers have been trouble free. And I flew airbleed for years with no complaints. They're not as easy to set, but once set are good. Matter of fact, since they work the same air density as the venturi, they're more apt to "follow" what the venturi is getting from the pressure/temperature changes. A low speed needle isn't. Of course, that's really academic since the lowspeed works just fine in it's environment.

Hey, I almost broke my leg checking out the bearing deal. Can I have the name of your insurance company? grin..........

BANJO,
Yup, the FL seems to have the same piston/sleeve TYPE that the OS-AX engines have. And the Surpass and Ultimate are ringed.

hmmmmmmm...... wonder if the Surpass uses a .91 ring...........

darn, this thread has turned into an hours worth of work!!!

OK, to make that clearer........

The FL piston/sleeve is an ABC (or whatever OS calls it) and the manual explains the breakin the same as they do in the .46AX manual. The FL would have a plain piston, no ring.

And after further checking (I ALMOST BROKE MY OTHER LEG!!!! running up and down them stairsteps!!!) the Surpass ring is listed in parts number sequence with the other Surpass parts. I'd guess it was a "normal" ring for that displacement.

Hey, BANJO, whereabouts around Burlington do you fly? I got a sister lives in Elfland (gotta call it that, she's my baby sister) and am over that way every so often. And what you got the FL70 on?

For the record, virtually all of our model engines have sleeves/liners. The castings would never take the abuse.

Darock,I fly at Copper Head field with BARKS club.Out off of hiway 54.I am only 10 minutes away in town.Let me know in a pm the next time you're coming and I'll show ya how to get out there.The FL is on a 40 Ultra Stik.I am flying both today and tomorrow after work.Flew yestarday too.In fact I fly almost everyday!