This looks great O.S.!!! Finally some new technology for 2 strokes.

http://www.os-engines.co.jp/english/index.htm

This is the second AX Series engine after 46AX.
Standard silencer is compact and easily enclosed in most cowls. Also, Extension adaptor and 90 degree adaptor offers several silencer installations.
Specifications: MAX-120AX RING

It is a torquer like the 1.6FX....usable rpm is only up to 9,500--small transfer ports(& case size).

If it is really only 21oz plus muffler that means with a good turbo jet it will be 28oz--same weight as YS110 and will beat it in power!!!!

2 strokes are back on top baby!!!

Notice no remote glow.

http://www.rcuniverse.com/forum/m_3380884/tm.htm

I can't say that I am pleased with some of the features of this new engine. First, the weight shown on the OS Web site is a contradiction. 647 grams divided by 28.35 grams per ounce works out to 22.82 ounces, not the 20.88 ounces shown on the OS Web site. I would think that the OS engineering staff can do better than this, so I'll blame their marketing department [8D]. I would tend to believe the higher weight of 22.82 grams because the OS .91 FX (25% smaller) weighs 550 grams or 19.4 ounces. Here is the link for the OS 91 FX:

http://www2.towerhobbies.com/cgi-bin...?&I=LXBY47&P=0

Second, five cylinder head bolts rather than six or eight bolts is a cost-cutting measure that results in more profit for OS/Futaba, not a better compression seal and longer lasting engine for the modeler. The OS 108, one size smaller, has eight head bolts:

http://www2.towerhobbies.com/cgi-bin...?&I=LXCK26&P=Z

While the OS 140 RX, one size larger, has eight cylinder head bolts:

http://www2.towerhobbies.com/cgi-bin...?&I=LXCK25&P=Z

and the OS 160 FX has six cylinder head bolts:

http://www2.towerhobbies.com/cgi-bin...?&I=LXUT09&P=Z

Third, even if this engine were to sell at a whopping 40% off MSRP or $270.00, it would still not be price competitive with other excellent engines in this class such as the Moki 135, Thunder Tiger 120, Webra Speed 120, etc.

Fourth, the standard muffler appears to be a copy of the Thunder Tiger 120 two-way muffler, but from the picture, it seems to extend pretty far down and could be difficult to enclose inside some cowls such as that found with an Extra.

To OS's credit, they finally moved the 120 AX needle valve to the right location.

Bruce

I think you can throw out the five head bolt issue, I have several SuperTigre, OPS and MVVS engines with four, never a problem and I think all my Enya fourstrokes have five. My two OS LAs .46 and .65 I converted to Diesel also have four head bolts and again no problem.

I agree with you on the smaller engine sizes. Bill W. designed the K&B Sportster Series with four-bolt heads, and of course, the OS 46 AX has a four-bolt head. But I think that when you start talking 120 size engines, the span between bolts gets pretty large with five bolts. It is probably OK for normal running, but what happens during a lean run or two? In this situation, more head bolts would help by providing more clamping points to reduce head warpage.

I am not an engine historian, but I can't think of any two stroke model engines larger than 120 size that have less than six head bolts. OS's competitors in this engine class use six bolts. Why introduce a new product at a high price against strong competition and have any potential liabilities? I happen to think that OS has lost the good engineering common sense that they used to have when they were privately owned. Just look at the mess they made with the last two 70 four stroke engines they introduced.

I suppose that time will tell as to the durability of the five-bolt head arrangement.

Thanks for your reply,

Bruce

cu.in

I don't apperciate your comments[sm=punching.gif]

1st, O.S. AX is a good series, specially now because they are using chrome on the 46 and instead of nickel

2nd, this wieghts less than the thunder tigre 120 or the ys 110!

3rd, Look at the cool muffler! Hell its a free inverted pitts muffler

4th, the lovley towerhobbies with thier nice 25-30 dollar off order on this engine will make it in the 220 dollar range for sure.

5th, I for one am really happy this came out 2-strokes are going to be king again.... muhahahahhaahah[sm=RAINFRO.gif][sm=RAINFRO.gif][sm=RAINFRO.gif]

Dang, I forgot all about the bad 70 four stroke that OS has come out with. I guess I was just expecting the best from them & wanting some new 2-stroke technology to hit the market.

Thinking about it, if OS were most concern about offering top performance they would have made the new .46ax maybe a .53 or a .56--maximized its displacement?

--------------

I have been thinking about the right prop for this motor and looking at its spects it shows max power to be a 9000 rpms and usable RPM rage to be 9,500 max. Not surprising as with its light weight it has to have small transfer ports which will cause the motor to go to sleep at high RPM. I would guess that the port timing compliments the small transfer ports making this a very torquey 120 2-stroke.

This being said, people that put something like a 15 x6apc on this motor will end up disappointed to find out it does not turn it any faster than a .91FX ( low 10's).

A 16 x6 will most likely be the a good prop to maximize thrust and still have the good forward speed, but I would guess it will pull a 17 x6apc with a little bit slower spool up. I am thinking a good 17 x6 Pro Zinger would be a very good prop as it would load the motor closer to 9000 rpm and still have fast spool up. Too bad that a 17 x6 is kind of an odd prop size.—cannot find it in a Pro Zinger or a wood Scimitar.?

A 17 x6 will be necessary if a semi tuned exhaust is used on this motor you will want to run it no higher than 9500 rpm to get max power.


Looking at Jett's 120 motor they show performance to be

BSE 1.20L R/C with semi tuned muffler AAC
16x8apc @9,200 27.8oz

http://www.jettengineering.com/

Disco Wings
What makes you think that OS uses chrome on the 40 AX?

here is a bigger pic:

I called hobbyservices and they said the Bi-Metal Liner is Chrome and 2 metals.
The original AX used Nickel, then they switch to "L"

Also, here are the prices:

269.99 O.S. 120 A.X. w/out muffler

299.99 O.S. 120 A.X. w/Muffler

TowerHobbies.com

Release date: Late November

The price is high but it looks to be a good design. I am looking forward to this engine coming out. I hope it runs as well on 5% nitro as the 160FX. The small ports should give good economy.

Yes. Although, I have found that the 108 gives great economy on a 10 pound plane and a 16 x6 prop & that has large ports. Will most likely improve though as you say.

How much do you think that stock muffler will weigh? It might be a real choker though as sound is more & more of an issue than ever. I think a good Jett muffler will be the way to go.

STG,

Like you, "I was just expecting the best from them & wanting some new 2-stroke technology to hit the market". I think that the engine will be just fine overall, and actually can't find anything else to criticize. FYI, the two-way, 90 degree Thunder Tiger 120 muffler weighs 234 grams or 8.25 ounces with mounting screws and lock washers. I would think that the OS 120 AX engine muffler would be close to this weight.

Disco Wings,

I guess you thought that I was bashing OS and the 120 AX engine. As far as OS is concerned, I still feel that they can do better, and I stated why. In the past, when OS was privately owned, I didn't think twice about engine quality or longevity, and OS was my number one choice. Back in the late sixties, I flew a Phil Kraft "Kwik-Fli" with an OS Max H60F R.C. cross-flow engine. I still have my OS 60 FSR that I flew in the seventies, along with numerous other FSR engines. I even bought a NIB 1940 OS K6 ignition engine. I'm not really that old....the engine is one of the few replicas that OS made of their very first engine that was built in 1940.

I have been an enthusiastic OS customer for many years, but I feel that they can do a better job on the products that they offer today.

Bruce

[b]Matt:

When I first saw the picture you posted I thought "Dang, OS is trying to `Outugly' the Evolution engines." On second look I decided that while they are trying, they haven't quite made it.

Disco:

OS is still using a nickel plated liner, there is absolutely no chrome in there. OS went to ABN cylinders, and didn't bother to change the ABC on the boxes. They got caught when the 46 FX engines started shelling their liners with amazing regularity, followed by many 91s, and other sizes as well. When they brought the 46 AX on the market they called it "Advanced Bimetallic Liner," but it was still the same cheapo nickel plating. OS has finally gotten their ABN quality up to the level of the Thunder Tiger's ABN cylinders. Maybe OS sent their engineers to Taiwan to learn how to do it - I've only heard of one TT liner failure, and that was foreign object damage.

Let's hear no more about the AX having a chromed liner, please.

Bill.

I'm with William, they are catching up on the ugly race with Evolution. To address some of my thoughts to one of the posts:

1, Like William said, No chrome in the AX. Last OS sport engines I know of that used chrome was the FSR's. I understand that some of the high dollar buggy engines use chrome plated sleeves.

2, I would venture tho guess that a great number of models that this engine would be suitable for would need the nose weight if this engine was used. Lighter is always better until you have to add dead weight to compensate.

3, Looks like a thunder tiger 120 muffler with square corners. Like the muffler's TT cousin, this one will probably prove to be easily vibrated lose and very leak prone due to too many screws and joints.

4, even if its at 220, OS has so many "OOP's" flawed designes out there to where I would risk 220. A TT 120 can be found for that or less and the Webra is out there too.

5, King again??? 2 strokes are king, look at the Moki 180 and 210, the Webra 160, the list goes on and on.

Lets hope that OS did something right for a new product (for a change). The last 9 OS engines I bought new were returned for service a minimum of one time. Three 46FX's and two 32SX's spit the nickle. The OS 70 heli engine could not keep a rod or bearings in it. The 160FX went back twice and was still junk after second brand new replacement. OS 50 could not keep bearings in it. And finally the wonderful new lightweight 70 four stroke that was a gift, it would'mt run worth a hoot. These engines all went back at least once and every time Hobby services was given the opportunity to return my money and keep the engine, which of course they refused. Only one of these engines I have now and that is one 46 FX that I forced HS to fix the peeled sleeve with a steel sleeve and a ringed piston (from the heli engine) and it still runs fine. The remaining engines went to ebay.

OS long ago forgot about the exceptional quality they built their name upon, now they are using thier good name to sell sub par engines. 20 years ago, I used to see the above types of problems I had, with other makes of engines, namely TT , ASP, Royal and the other OS want-to-be's. Now, look how the tide has turned, the once great OS quality is worse than even the average Chineese engine.
l was an OS fan, that's why I gave them so many shots to keep my business, after all, I am still running a Hanno 60 on a regular basis and two 45 FSR's very regularly. But when they get tired, that's it, no more new ones. On twelve current planes and helicopters, the only OS's I'm running are the FSR's and the Hanno, no modern OS's.

Too many good motors out there to be bothered with sending them in for warranty work. Buy an Enya, TT, Webra, Moki, MVVS, Saito, YS and yes, even a Fox, same or less money and light years ahead in quality.

[b]If you want an engine with a cheapo ABN cylinder just buy a Thunder Tiger and be done with it. Still a good reliable engine. You'll save a bunch of bucks too.

Bill.

[b]I have to be fair here. A local flying buddy who is also in twins has been having engine problems in them. GMS 32 engines shelling their rod bearings, the Magnum XLS 52s wont run together, but his planes running pairs of the OS 46 AX engines just keep going. He says he's becoming an OS fan.

As far as I know he's not tried the Thunder Tiger engines.

Bill.

Its funny you say that William, my OS 32SX's were bought as a pair, broken in as a pair and used on a twin where they ran identical. They ran great and always did everything together like idle, transition same top end and they both spit the nickle out within three tanks of each other in exactly the same spot just above the exhaust port. Now, to be fair, the 46FX's that had new ABN liners put in them (two of the three, the third 46FX was converted to the ringed version at my request), ran fine, but by the time I waited almost 8 months to get them back (HS did not have any parts because lots of FX liners were spitting the nickle), I lost all interest in keeping them long enough to do it again and were promptly sold.

....If they would only make an engine of the caliber of the Hanno's or the FSR's again.

If in fact this, or sould I say these are the prices IMO they are ridiculous! Looks like a decent prospect but the price is way out of line...

[b]Doc:

In twins I have K&B 40s and 61s, Magnum XL 46s and XLS 40s, one has a pair of HB 25S engines, I even have a pair of AMD (Norvel) 061s in the Tiggerkitty (See my avatar).

Now my shameful secret. I have a pair of OS 15s for my incomplete Duellist 2/15 prototype. But they are the iron piston/steel sleeve Max III versions so they will be fine. They are NIB even though they are more than 30 years old.

None of these engine pairs has given me any problem in normal use, but I have to admit the Tiggerkitty's engines are about run out. They are 13 years old, so I suppose that's OK.

OS needs to do two things for me to go back to them. One, look at the market and adjust their prices accordingly, and two, put the chrome back in.

Bill.

I meant King in power to weight. And I was comparing a 2 stoke with stock muffler on 5-15% to a 4 stroke on 30%.

Right now I think the Kings are:

18oz- YS63, SA82
21.5oz- SA100
27.5oz -YS110
33.5oz -YS160 and YS140, SA180
42oz -SA220

---------------------------

The education you guys are giving me on O.S. is really spoiling my fun.[] I have had nothing but great running motors so far.

O.S. 25fx --only mabey 1/2 gal thru
O.S. 46fx --8 gal thru
O.S. .91FX - 7 gal thru
O.S. 108fsr - 10 gal thru
O.S. 1.6FX- 10 gal thru

If nothing else it has cemented my feeling that I did not want to pay very much for a used motor that did not come with a manufactures warranty.

I was looking at this 120 to be a replacement for my 110 thinking it would have similar power to weight.

I guess it will cost ~$250 to my door and another $100 for a Turbo Jett muffler or $350.00

Maybe I will look at the Jett 120 again for $399.00 with the turbo jett muffler. [&:] I just don't like that it is not a ring motor at this large piston size, but I guess the guys at Jett most likely know what they are doing?

Maybe I will pay the 5oz weight penalty and get a Turbo Jett for a 108FSR. I am pretty confident power will be similar.

I'm not a historian either but I will tell you this story. I think many are forgetting when the 91fx came out. I owned two of them within the first couple months and returned them both with overheating problems and I was not the only one. This new 120AX has "pick me! pick me!
written all over it. I have several OS's and a big fan but the 91 fx is not reliable at all

I suggest you guys leave this thing alone for a while until all the suckers buy one and see how it goes. Design may over come the need for more head bolts. Whatever the case, I am sure that a G2300 at half the cost will have equal or better performance

STG,
5 ounces of weight is generally insignificant for an aircraft that would be of size enough to accept a YS 110. You could help make up for it by use of lighter servos, lighter battery, and so forth. The OS 108 is one of those that is on the good list in my book, they're very nice engines. Forget the Jett muffler (and depending on your application) use a Macs header with a moose can pipe, very light and effective.

Did not mean to spoil your fun. For the past few years I have been paid to test run engines for a model fuel company. Since I have my own private flying field and am out in the middle of nowhere and retired, I can do this till my heart's content and not bother anybody. Mostly I run them on the several engine test fixtures, then a few of them I will actually fly on one of my planes or heli's. I even have a set of load beams to mount on car engines and a ducting system to cool the head when I test run them. I have gone through lots of engines, some were good , some were junk.
I use as a baseline, the average 40 size two stroke will run 15 minutes (at varying throttle positions) on 8 ounces of fuel. My goal is to get 400 hours on an engine or 100 gallons, whichever comes first. I have had numerous engines make it past this mark and a few that did not. To be be fair, I do a few things that the less experienced modeler does like shut them down for the day and do nothing to them until they are run the next day, I also run them a bit lean but only to the point where the rpm's are peaked, not past peak and generally use a prop that is on the small end of the scale for the given engine. I do run them on a fuel type that is intended for that design or recommended in the instructions. and always two identical engines are run identically at the same time, one with a competitors brand fuel and one with the company I'm contraced by, just for comparison.
Anyway, to make a long story short, I have run the engines you mention above and a bunch more of the OS line, this is what I got before the engines just simply wore out:
25FX- got to about 6 gallons
32SX- got to about 20 gallons after the first set of sleeves
40FX- got to about 20 gallons
46FX- (early ones) about 6 tanks
46FX- (later ones) about 40 gallons
OS 50- (airplaneversion and heli versions)- could not get past 10 gallons without it puking the bearings, longevity testing suspended on the modern OS 50
61FX- got to about 65 gallons
OS70 Heli-got to about 3 tanks on both engines, rods gave out. replacement engines made it to about 15 gallons
91FX- got to about 35 gallons
160FX- (after several tries and replacement motors, testing was abandoned)
OS 120 Surpass III- bearings failed around the 15 gallon mark, heads warped around the 50 gallon mark
OS 91 Surpass- got about 80 gallons before it was just plain worn out
OS 70 FL- after about two gallons of frustration, testing was abandoned.

As a comparison, heres some of my test engines that are in either the 400 hour club or 100 gallon club
Fox 35 CL, 40 bushing, 40BB, 45, 46, 50 and 74
Enya- 25, 40's (all the 40's), 50SS, 50CX, 60 (all versions) and 4-strokes: 46, 53, 90, 120 (old and new) and the 155 (everything tested)
Irvine- 46, 53
Super Tigre (italian)- 34, 40, 45, 51, 75, 90, 2300, 4500 (no chineese ones tested yet)
K&B (Pre Mecoa)- 40 (4011), 48, 61
Thunder Tiger- 25, 40, 42 bushing, 46, 61, 65 bushing, 120 and 4 strokes: 91 and 120 (everything tested)
Magnum- 46 (the only model tested)
Webra- 50
YS- 45, 53, 91AC
Saito- 56, 65, 72, 80, 91, 100, 120, 180 (everything tested)
Moki 135, 180 (everything tested)
MVVS 40, 49, 77, 91 (everything tested)
Rossi 45, 53 (everything tested)

Now heres some that did not make it to the club:
Anything Mecoa
Anything Leo
Anything MDS
Anything OS (modern)


Don't flame me guys, these are just the results experienced. In all cases, fuel should not have been an issue since failures in the OS line on one fuel were very soon repeated on the other, which indicates design problems.

[b]Doc:

Maybe I've just been fortunate, or possibly I've only gotten old stock, but everything K&B and HB from Randy Linsalato, owner of RJL Industries. MECoA, and associated names, has been of the same quality I had gotten from the independent companies. No degradation in quality or working life that I've noticed.

Bill.

Bill,
My refrence to the " Pre- Mecoa", I should have clarified that the K&B engines I had tested were before the company was bought by Randy.
My Refrence to "anything Mecoa" not making it into the club, I should have clarified that any engine with mecoa cast into it, not the entire umbrella of the brand names Randy ownes. I ran the 46 and 61 Mecoa brand name engines and they were OK, nothing spectacular but made it past the 70 gallon mark before they just wore out. I have heard nothing bad about the K&B's, and HP's he's producing, but have not run them either
I have an HB 61 PDP engine, its my own, not a test engine, it is from before Randy bought that company too, it still runs great, I do not have a Mecoa built HB 61

I am sorry for any misunderstanding, I should have been a bit more specific when referring to the above.