martinoto

Romeojack,
Please, see the date of previous posts. The Ultimate was changed around late 2005 and the "new ones" works fine. See the following post where I asked Bax about it:

http://www.rcuniverse.com/forum/m_6183014/tm.htm

I have been following the threads regarding this engine, because I had a good offering from my LHS at this time. As far as I understand, original versions of the Ultimate were hard to tune, and many were crap. Evidently, OS noticed and changed something, but it is unclear to me what was it. Truth is now the Ultimate works fine and reliable. Only concern is to get one of the new version, which is a problem you could have in small dealers whom has this boxes in stock for long periods, since OS did not made a full recall.

So don't get mad at the people who made their opinions here, you both are most probably right.

Hope it helps.
Regards

rexracer

I love how a guy with 1 post comes in and puts down a bunch of people who I KNOW from previous posts have tons of experience with these engines. I don't have this engine, and I never will because if people with this much experience are haveing problems with it, then there IS a problem. There are too many engines, OS and others, that run trouble free for me to waste my time and money on a "Maybe".

rainedave

My Feedback: (1)

It would be very useful to see a photo of both versions side by side. Did OS change the location of the pump to protect it from overheating, i.e., are the changes externally visible?

Thanks,
David

togatoga

My Feedback: (42)

No external differences that I know of .They reworked the internals of the pump I think to prevent heat vapourisation of the fuel. The part numbers are still the same though ,although post 2005 manuals show that you can only purchase the pump unit whole that is backplate and pump unit- not separately.
I got a couple of post 2005 engines and they run great. Still prefer the YS63 though, just needed something different to play with!

martinoto

David, I was trying to find the post were Bax talk about the new model, but I couldn't find it.
I remember thou that the changes came in the pump, as Togatoga said.

romeojack

My Feedback: (3)

romeojack has been flying for 26 years maybe i just got a good motor ive tryed ever combation from low nitro to 15 inch props but always 18% oil s/c mix sorry for those who didnt get a good motor ive never had a nitro motor any better thanks OS

maukaonyx

Wow, I should have done more research before getting a used, like new, one of these engines six months ago. I finally installed it in a plane this weekend and cannot get it to run right. It exhibits the probs noted by others....sensitive needle, richens till it dies, extreme high pressure in the tank and tubes. I thought I got a a nice engine...looks like I got crap. I always thought of OS with the highest regard, but seems they can put out crap too, at least on this one. I must have an older version, and got taken by the seller on RCU. It was so appealing...high power, low weight, decent price. Buyer beware...I didn't think too hard about buying an OS engine, thought I couldn't go wrong. Now I have to figure out whether to keep trying (knocking head on stone wall) or try to pawn it off on another dummy like me, and put in a regular Surpass II black top which weighs 4 ounces more! I never had as many engine probs as with this engine and the one that it replaced, an FL-70. If anyone has the miracle cure yet, please offer it up! Thanks.

asmund

Go out and buy an "old" OS 91 FX to replace your 70 ultimate and see if it is any better, he he
Can OS put out crap? Oh yes you better believe it. They have many great engines too of course[8D]

OS is NO guarante of success I`m afraid

maukaonyx

Not sure if you are being sarcastic about the 91 FX since I am not familiar with it personally. Is it good or bad? Answer is moot since I don't want a two stroke for this plane. I have a couple OS 70 Surpass II (black top) so I might just have to put one of those heavy weights into my Excelleron 50 and sacrifice lightness. I figure the engine weighs 4 ounces more, plus I will need between an ounce or two in the tail to maintain my CG. Rats. It's better than not flying it at all.

asmund

I was only kidding they had ALOT of problems with the early 91 FX`s (I have one myself, took a carb swap to fix it, now it is great) I was just pointing out that the name OS is not always a guarante of a fantastic engine. The 70 Ultimate is notorious for having issues and was soon discontinued by OS for that reason.
You might get it to run as intended (a few have been successful) but chances are that it never will run right I`m afraid

If you need a lightweight powerful fourstroke that can swing a fairly big prop, I really think you should have bought a Saito 82

togatoga

My Feedback: (42)

Think of it as a YS engine. Needles lag in adjustment and more sensitive than usual.You need to wait a while for the engine to react . Try a light load initially on the engine. Problems of the older engine was when the engine got too hot and affected the pump. The pump system actually pressurizes the tank, so it must be airtight with no leaks. The one outlet that lets in ambient air must be kept clean or it'll cause problems to no end. There's a lot of engineering gone into the engine, unfortunately it didn't result in a user friendly engine.The pump system was a one off thing for OS,complicated and too expensive to replace.

maukaonyx

Thanks guys. I don't want or need a lot of stress and tinkering for what is supposed to be total relaxation. I already ripped the engine out and will have to build new engine mounting for either the OS 70 Surpass II or another four stroke of appropriate size, weight, and power. I am going to look around now for alternatives.

asmund

For light weight, powerful engine below the 91 size there`s really only two candidates: the YS 63 and Saito 82.
The YS will swing a smaller prop (13-6) at a higher rpm and the Saito will swing a normal 91 prop (14-6) at lower rpm
Don`t be fooled by OS`s new 81 size, although it propably is a great engine ( but very expensive) it is considerably heavier than the other two I mentioned (despite OS claims otherwise)
There`s a thread somewere on this forum showing all thre of these engines and their actual weight.

tadatuo

Thanks asmund. Overnight I have been looking around for alternatives. I think you are pretty right on about the options. I am leaning towards the Saito 82 AAC. It's as light as the Ultimate and even more powerful. Wish I could find a gently used one. Do you know how good that engine is? I don't want to run into another mistake like the FS-70 Ultimate! Thanks guys.

asmund

You can find ALOT of info on the Saito 82 if you use the search funktion in this forum. People seem to be very happy about this engine. It is not a very intricate engine like your Ultimate or the YS 63, so less things can go wrong with it and it is easier to isolate a problem if there is one. Will run fine on 15% nitro and propably less too if tuned correctly, but will deliver max power with more nitro up to 30%

sseward

My Feedback: (1)

I've been struggling with my FS-70 ultimate for a year, and I've concluded I have on of the earlier models. It runs great when cold, but when it heats up it starts stuttering out.

I thought I read in the manufacuters forum that Baz said the only differnce is the pump unit....the rest is the same. The pump is available for $88 from Tower. Is it worth it to try and change it out?

The first minute or two of flight, when it's running, I'm very happy with it.

Steve

the pope

Dont hesitate getting the saito 82 I have one and its fantastic. Ive never had a dead stick and the only time it wont start is when I forget to turn the plane on . Cheers the pope

maukaonyx

Guys, I decided to put the heavier OS 70 Surpass II into the Excelleron 50, replacing the Ultimate 70. Had to add some tail weight too for the heavier engine, but it runs great and seems to fly the same. I did get a nice Saito 82 off here the other day, and it looks like new for a used price. I will keep that for another plane unless something unexpected happens to the Surpass II. Jon

martin_solo

I convert OS 70 Ultimate to use in Control Line models and in the process I remove the carburator and the coverplate with pump and replace with other parts I make. So I have a few sets of carburators and coveplate w/ pumps that are new removed from the latest engines. Would any one be interested in getting these parts? If so please enter in contact directly with me at martin (at) stunthobby.com


Martin