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OS 70 Ultimate w/pump

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Old 07-18-2006, 12:26 AM
  #1
AmirN
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Default OS 70 Ultimate w/pump

Curious to see what experience people have with this engine. Reliablility, power (RPM, fuel, prop if possible) , needle sensitivity & anything else you're willing to share about the engine.

Thanks in advance,

Amir
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Old 07-18-2006, 05:15 AM
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Harry Lagman
 
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Default RE: OS 70 Surpass Ultimate

Amir, I will assume for the purposes of this post that you are referring to the OS .70 FS70 Ultimate (not Surpass) engine with the blue rocker cover and the pump.

I have worked on just one example. I started this engine for its first run for one of the guys at the field. For its first 15 minutes of runtime, this engine was almost impossible to dial in. It would run OK when started then when you tried to dial in the main needle for a rich full throttle run, it would approach peak then without any warning would drown itself with such a rich mixture, it would stop dead, completely flooded.

After restarting, I tried to redial the engine on several occasions and it was all over the place. Eventually, the owner was keen to get her in the air and I set a very rich mixture that seemed to be sustainable over time (in other words, it didn't drown itself out of the blue as it did in the earlier runs). Amazingly, once in the air, it leaned out some, and ran really well. Two flights later it went in hard (dumb thumbs - no fault of the engine) and snapped the carb mount tang from the backplate.

The owner ordered a complete backplate/pump assy and fitted it. A flying buddy and I ran the engine in a test stand with its new pump and guess what - it ran as sweet as any four-stroke I've ever seen. On 15% nitro, it pulled 10,200 rpm with an APC 12x8 (comparison: 9,900 for a Surpass .70 on 15% nitro and 10,600 for a YS .63S on 20% nitro) and idled at a rock solid 1700-1800 rpm with perfect transition. This engine is about to maiden in an Acro Wot so stay tuned for the report.

So where am I going with this?

Well, the OS .70 Ultimate seems to be a bit of a dice throw - it could run like a dog or it could run absolutely perfectly. Unless you are a real "engine guy" who is not scared of persevering with an engine that is not running right and who takes pride in fronting up to the field with an engine that's a little different, I would not recommend buying one based on my experience.
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Old 07-19-2006, 02:38 PM
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Default RE: OS 70 Surpass Ultimate

I had an OS 70 ultimate and did not like it one bit. Lots of dead sticks and starting it up made me nervous as it liked to throw its props.I ended up selling it and putting the money towards a saito 82.

Leigh.
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Old 07-19-2006, 04:10 PM
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Default RE: OS 70 Surpass Ultimate

Great planes discontinued the Ultimate after so much trouble.

Buy a Surpass 70 or a Saito 82
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Old 07-19-2006, 09:13 PM
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Default RE: OS 70 Surpass Ultimate

I'll second that for the Saito 82- you won't regret it.

I had a 70 Ultimate with the blue head, never could get it tuned, finally sent it to Hobby Services and they gave me a 91 Surpass in trade. This motor was discontinued because almost no one could get it to run well.
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Old 07-20-2006, 01:49 AM
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AmirN
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Default RE: OS 70 Surpass Ultimate

Harry and all the gang who took the time to write, a big thanks!

Yes, I did mean the blue head OS .70 pumper. I did run a bunch of OS 4 strokes and the non-pumpers have been very reliable & consistant. I've also read just about all the posts I could find on the Saito .82 on RCU....I've seen Saitos run, and tuned a few for local fliers, sweet engines. Even had a 300 twin a few years back. I was leaning (a little pun) towards the Saito 82 myself. It'll be going in an Exelleron 50....anyone flying or seen the Exelleron 50 & Saito 82 fly?

Thanks again,

Amir
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Old 01-17-2008, 09:23 AM
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Default RE: OS 70 Ultimate w/pump

the saito 82 has a spot where it runs rough. the os 70 ultimate has the power where the saito can not touch it. i use saitos and they are great engines. but the 70 ultimate will run circles around the 72 saito. the os has more power verticle in a hover. but the saito is hard to beat. i have had a saito 220-180 several 150's a few 72's and 1- 82 they are the best engines with out a dought. but the os 70 ultimate with a pump has more power. it is a sweet engine. i have two friends that have them. I went with a 72 saito on a profile omp edge, they have more power than I do. I also have a os 55ax with a ultrathruse muffler.
no one needs more power than that has.
good luck I THANK I WILL GET THE OS 70 ULTIMATE NEXT IF YOU HAVE ONE LET ME KNOW. BECAUSE I LIKE A 4 STROKE TORQUE. BUT THE 55 WITH A PIPE IS SWEET.
HOLLYWOOD
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Old 01-17-2008, 09:32 AM
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Default RE: OS 70 Ultimate w/pump

DOES ANY ONE HAVE THE 70 OS ULTIMATE 4-SALE FOR A GOOD DEAL?
IF SO PLEASE LET ME KNOW AT
BROWNSFLOOR@BELLSOUTH.NET
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Old 01-17-2008, 09:44 AM
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Default RE: OS 70 Ultimate w/pump

LXXA42 O.S. FS-70 II Surpass
Accessories Needed Possible Substitutions
Discontinued
THE SURPASS IS THE ONE THAT WAS DISCONTINUED.
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Old 01-17-2008, 09:59 AM
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Default RE: OS 70 Ultimate w/pump

Hollywood,
If you look at the date of the early posts in this thread you will see they were made several years ago.

After the OS 70 Ultimate was introduced, Hobbico decided to discontinue selling it because they would not run correctly. They were discontinued for 2 years before Hobbico/Tower started selling them again.

Now that they are trying to sell off the remaining OS 70 Ultimate production, there is a new model out and the OS 70 Surpass II has been discontinued. The Ultimate will be discontinued also as soon as they sell off the inventory.
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Old 01-17-2008, 03:38 PM
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Default RE: OS 70 Ultimate w/pump

DO YOU HAVE ONE. I NEED ONE. IT IS SWEET

IF ANYONE KNOWS WHERE I CAN FIND ONE OF THE OS70 ULTIMATE ENGINES,
PLEASE LET ME KNOW.
THANKS[sm=wink_smile.gif][sm=wink_smile.gif]
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Old 01-19-2008, 01:34 PM
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Default RE: OS 70 Ultimate w/pump

Tower has them. Any GP dealer can order one.
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Old 01-19-2008, 01:51 PM
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Default RE: OS 70 Ultimate w/pump

You can get a YS .63 that will run circles around the .70 ultimate any day of the week. I would not go out of my way to purchase an OS that is on the way out. From past history with discontinued OS were parts are non esistant about a year later. Then you have a nice paper weight. Try to get parts for the pump or regulater. You cannot without buying the complete assemblies. Look how OS discontiuned the best carb they ever made (OS 7D) as fast as the 1.08 was discontinued. Parts are allready limited stock and that engine is still very popular. Atleast you can get parts for a YS that is 10 years old, and a cheaper price than you will ever buy anthing for a OS.[X(]
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Old 01-19-2008, 03:23 PM
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Default RE: OS 70 Ultimate w/pump

Quote:
ORIGINAL: hollywood III
IF ANYONE KNOWS WHERE I CAN FIND ONE OF THE OS70 ULTIMATE ENGINES,
PLEASE LET ME KNOW.
THANKS
http://www3.omnimodels.com/cgi-bin/w...I=OSMG0875&P=0
In Stock
Price $299.97
Free Shipping
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Old 01-28-2008, 12:02 AM
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Roary m
 
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Default RE: OS 70 Ultimate w/pump

Just bought one at ultimate hobbies online; 229$ plus tax.
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Old 10-28-2008, 06:03 PM
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Default RE: OS 70 Ultimate w/pump

I have a FS 70 ultimate with pump blue head. Runs great, no dead sticks, ran right out of the box, I have put about three gals of fuel through it. Here is the problem... if I leave the engine for a week then it will not start.... reason no fuel is getting into it. If I turn over the engine with a starter the pump pumps fuel to the carb. The way I start it is to inject some fuel into the carb from the flight box pump then it starts first time. Now it runs and starts first every time for that day. But if I leave it for a few days it will not start without an injection of fuel direct to the carb from my flight box pump. Anybody else had this problem? Another guy in my club has the same problem.
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Old 10-29-2008, 09:23 AM
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Default RE: OS 70 Ultimate w/pump

The problem is that fuel in the pump/regulator system dries out and you have to turn the engine over a bit to get fuel back into the system. The best way to get fuel back in is to open the carburetor to full, choke it with a finger, and turn the propeller over by hand in the normal forward direction. This will eventually draw fuel into the pump and carb system, and then up, into the cylinder. When you can hear fuel spitting out of the exhaust port, remove your finger from the carb intake and briskly flip the propeller forward through compression several times. Now retard the throttle to just above idle, attach the glow plug battery, and start the engine. The pump needs to be primed, once it's become dry of fuel.
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Old 12-08-2008, 05:28 AM
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Default RE: OS 70 Ultimate w/pump

I had problems with this engine but once the plane was in the air it went fine. It never cut out on me. i had trouble setting mine because it was mounted inverted. works like a dream now though
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Old 04-20-2009, 01:06 PM
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Default RE: OS 70 Surpass Ultimate

My Os fs .70 ultimate engine with the blue head works a dream. I bought it at Christmas and i put on my Black horse chipmunk. I had a bit of running problems to start off but i took it upto my local club and the club trainer had a bit of knowledge on 4 strokes. He had to completely re tune it after the 3 tank running in period the engine still is running with 6 tanks having run through. My engine has loads of power and is running better than any 4 stroke i've ever had. My Chipmunk is super aerobatic and can do loads of 3D and aerobatic tricks i can do super fast barrel rolls and it flies straight. I think this engine is great and you just need to get someone with experience.
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Old 09-30-2009, 12:06 AM
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Default RE: OS 70 Surpass Ultimate

The OS FS .70 Ultimate has a "bad rap" for some reason, and it's completely unfounded. This was is outstanding motor for something just like the Seagull Edge 540 (which is, coincidentally, what mine is stuffed into). People who don't don't have the mechanical ability to understand small precision devices like the Ultimate shouldn't expect to be able to master a mechanical jewel like the four-stroke Ultimate .70, let alone maintain it. It was replaced more because of the .82 being larger, I suspect than any clandestine "scheme" as was implied above in another post. Those less mechanical folks should fly electric, or alternatively, get a Super Tigre 2 stroke.... which is comparatively easier to tune, and simple to maintain.
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Old 09-30-2009, 12:21 AM
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Default RE: OS 70 Surpass Ultimate

You are most fortunate to have a Ultimate 70 with a good regulator in the carb
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Old 09-30-2009, 04:11 PM
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Default RE: OS 70 Surpass Ultimate

I find it strange that OS has the 91 pumped 4 stroke which runs very well; I don't understand where they missed on the 70. I haven't gotten around to running mine yet.
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Old 10-01-2009, 02:50 AM
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Default RE: OS 70 Ultimate w/pump

Point of fact: The OS FS .70 Ultimate has no regulator. It's just a pump, at least according to OS. The carb's needles take care of the fuel metering as they normally do in carburated internal combustion engines.
There is more than one seal in the carb, too. A vacuum leak due to crash damage, unnecessary disassembly, or improper reassembly can screw up any motor. Just like a fuel line leak can make any motor "impossible to tune". There are a lot more fuel line connection points because of the pump than a simpler two stroke without a pump. When something complex looking doesn't work the way people expect, or want it to, they usually look for excuses before examining the simple things. Like air leaking into a fuel line where you can't see it...like in the back of the motor.

AS MR. BILL B simply stated above: "The problem is that fuel in the pump/regulator system dries out and you have to turn the engine over a bit to get fuel back into the system. The best way to get fuel back in is to open the carburetor to full, choke it with a finger, and turn the propeller over by hand in the normal forward direction. This will eventually draw fuel into the pump and carb system, and then up, into the cylinder. When you can hear fuel spitting out of the exhaust port, remove your finger from the carb intake and briskly flip the propeller forward through compression several times. Now retard the throttle to just above idle, attach the glow plug battery, and start the engine. The pump needs to be primed, once it's become dry of fuel."

It took me a while to get used to pumped motors, but after learning how to tame my trusty old HB .40 with the PDP carb and pump, I can do anything, except speak French in Russian.
javascript:void(AddText('','_image/s4.gif')) Maybe it's a case of a leaking pump gasket, who knows? The sell 'em at Tower. I've never taken mine apart, maybe that's why it works.
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Old 10-01-2009, 09:19 AM
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Default RE: OS 70 Ultimate w/pump

The OS 70 Ultimate has been discontinued by Tower

When first introduced it had a very checkered success whereby Tower Took it off the market

After more than a year, Tower again offered them for sale and the engine performed better with some improvements and tuning instructions

The problem area tended to center around the combined Regulator/carb which is no longer available as a spare part

The carb was a slide valve type rather than having a rotary barrel as in most model airplane engines

By the time the engine was running better, other brands including newer OS models had arrived on the market to have more power

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Old 10-01-2009, 10:47 PM
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Default RE: OS 70 Ultimate w/pump

Okeedokee, now the gloves are off Mr. Moderator Man.
Spend a couple minutes and do the research before you spread the BS about OS (and Tower). Here is the link to Tower's OS .70 Ultimate spare parts page. http://www3.towerhobbies.com/cgi-bin...NUFACTURER=OSM They have every single part in stock. Including the Pump. As far as I can see, "Club Saito" must exist to bash other brands? Geez. That's really productive. Tell you what, even though I only own one OS, I'll be certain to remember the Saito Club Logic, and never buy an overpriced Saito. BTW, In case you haven't noticed, Chevrolet no longer makes the 1967 Corvette Split Window Coupe. The USAF no longer flies the P-51D Mustang. Try and buy one of those, and you'll see that just because something has been replaced by another thing, bigger and more expensive, doesn't mean the original "probably doesn't run good".... Both the Split window, and the P-51D are nearly impossible to find, and cost fortunes..."used".
Don't bother arguing with me, I've got better stuff to do, like fly my OS .70 Ultimate...vertically....for hundreds and hundreds of feet straight up. Cheers.
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