Have we talked about this engine yet? It seems so hard to search within an aera and find anything?
http://www.os-engines.co.jp/english/081010/

http://www3.towerhobbies.com/cgi-bin...?&P=G&I=LXWHW8

A great deal of the parts are common with other OS four stroke engines

Nice looking engine. Velocity stack, cooling fins on cooling fins (they forgot the rocker cover), nice intake and exhaust manifold attachment points to the cylinder, glow plug in it's proper place. Do .71s cost that much these days? Wow.

Bill

Figures are with apc 13x8 - 9850rpm and apc 14x6 - 9360 rpm. Quoted in a jap magazine review. Exact mounting holes as the fl70. A replacement for the 70U which like the fs200FI are now discontinued.

Those are impressive rpm numbers but I wonder what we will git?

I mentioned it in a thread back in the spring. I said something negative about the price and caught he**. It would be nice to see some real world RPM numbers. It may be worth a little extra green for a stout reliable 72 size. For now I am happy with the Saito 82.

david

I know O.S. Max makes great engines, but:

$339.99 - O.S. Max FS72-a (Tower)
$259.99 - Saito .72 (Horizon)
$259.99 - YS 63s (Central Hobbies)
$209.99 - Thunder Tiger F-75s (Tower)
$179.99 - Magnum XL .70 RFS (Tower)

At $80 more than the Saito .72 or YS 63s and almost double the price of the Magnum XL .70 RFS, I don't know I'll be seeing a lot of these FS72-a four strokes at the local fields. Tower is selling the TT F-75s at well above the regular $169.99 street price, but even at Tower you'll save enough over the O.S. Max FS72-a that you could almost buy an extra .55 AX 2-stroke.

There is a coupon code for $60 off $300 or more right now (01440 for Super Saver members), so $279.99 doesn't seem quite so outrageous for the FS72-a. If Tower has to jack up the prices of their products simply to account for their own coupon/discount promotions, however, I'd suggest that they simply offer fair pricing to begin with.

The price really is a bit unreal. Now, to be fair, Horizon does have a "list" price of $415.99 on the Saito .72, but that's no where near what anyone (Horizon included) sells them for. Is Tower selling OSes at list prices, and hoping that a percentage of customers will pay it? Of course they are. Tower provides regular discount codes for those that care to find them, bringing the products to "street" prices. Customers then feel as though they're "saving." How many times do we see that phrase here in the forums? It's akin to "winning" an auction. Marketing at work, eh? The really sobering thing about Tower is that they apply their discounts not to a given product or line, but across the board. Their pricing is 20% above street price on everything if you apply the discount coupon percentage. Isn't that comforting when placing a small order? "Oh, but you should buy in bulk..."

Between the increasing prices for the engines themselves and the cost of high-nitro glow fuel, I think we're beginning to see the end of glow. Electric is a real alternative, and for the price why not go gas? For me, a lack of physical space is the only reason I haven't gone gas.

One has to wonder if companies tied to glow, such as OS, are happy with the pricing provided by their US importers. The US importer doesn't care if their revenue comes from glow, electric, or gas modeling. OS sure must care about the future of glow, however. Their ducted fan business is largely done, they don't develop gas/electric/turbine products, and their only other business line is miniature steam locomotives.

The 72 was just put on the Tower site yesterday according to their details. I think it was on the Japanese site on January 8

I have not noticed any of the new OS four stroke engines in the market place yet

It's been on the Tower site for several weeks, but as a placeholder with just the photo and price prior to yesterday. Been on the OS site for at least a month or so. I remember wondering why Hobbico wasn't importing them, back before the placeholder was on Tower.

Hello; Can that engine be mounted any way but upright? Will gravity interfere with OS' much publicized oiling system? I think so. So all you potential FSa 72 owners really want an engine that can only be mounted upright? Or are OS hoping no one will notice this little oversight? Why has no one thought of that yet?

Doc, go into more detail about the inverted problem?

Do you have a problem with an inverted installation. Do you have any details you'd like to share? The manuals for the currently available Alpha series do not warn against inverted mounting. I have my FS-52 with the same oiling modifications mounted sideways and didn't see any issues. There have been a couple Alpha series on the marketplace.

I found the 56 with the broken back plate

There was just an FSA-81 listed sold for $265 NIB. Good deal, but I couldn't do it right now.

I pays to keep an eye out there

Hello; The way I understand it, the final port for the exiting (used) oil is in the bottom of the chamber containing the valve rockers. That oil won't go to the bottom of that chamber if the engine is inverted or side mounted, at least it won't until the chamber fills up entirely. I hadn't considered that the rocker chamber filled with used oil. That oil would eventually leak into the intake tract, and perhaps find it's way out of the engine through the carb, or even into the combustion chamber, if the engine stopped with the intake valve open.

The old OS Surpass I engines had the crankcase nipple on the bottom of the engine. If these were inverted, the nipple was on the top of the engine. This fact of the nipple being on top of the engine never caused any problem with the engine filling up with oil. They still blew out oil.

Couple of questions: Where does the oil go in a conventional 4 stroke? Does it just fill the rocker cover-of course. I have been flying a 56 upside down for some time without any issues. OS has run them every which way before they released them. That is what an R&D dept is for.
Oh buy the way I also fly Saito's.

L.

I'll say this, it ain't easy to cut the electrodes necessary to make molds like that. Carbon or Copper. The mold work is Killer!!! The flash seams are so very very thin.

Oil that is expelled by the crankcase finds its way via the pushrods and is sucked in the hole in the intake valve.The oil exists in vapour form i.e atomised droplets and is drawn into the combustion chamber during the down stroke and pressure differential that exists.It will be independent of the engine position. Oil residue in the rocker case inevitably will reach an equilibrium. I have run my setups in inverted mode and it has never been an issue.

You don't need to worry about it. The pressure inside the crankcase that's caused by the pumping action of the piston going up and down will drive oil throughout the engine. The front bearing will get lubed, the cam bearings, the valve lifters, the pushrods and rocker arms, and finally, the valve stems. Even oil will find its way up, inside the piston to lubricate the wrist pin/rod junction.

You may rest assured that the only problems involved with running any O.S. engine inverted are those people have had since glow engines were invented...if you don't have it broken-in and tuned correctly, you'll have difficulty with idle and acceleration because the glow plug will become the lowest point in the fuel system and tend to "load up" at low-to-mid-throttle settings.

Is anybody running one of these?

Yep,

I have one on my Great Planes Big Stik 40.

I'm still running the engine slighty rich and haven't peaked the top end yet, but so far i've had a half dozen flights and its going great. I'm using an APC 12x7 and it pulls that 5.5lb plane around like a pylon racer and makes it a blast to fly. I'll probably move to a 13x6 to slow it down some for the club fun fly events.

A local magazine reviewer recorded the 12x7 at 10,700rpm on 10% nitro. I set my needle so that it held an even 10,000 for the break-in flights and that was slightly rich.

The idle on my engine still needs to some adjusting and this weekend i plan on getting those needles tuned right.

The engine sips fuel even when running rich. I flew for 10 minutes and come back with 1/3 of a tank each time.

I like this engine so much i'm going to get another and put it in a Kyosho Osmose. It should be a good match.

I recently disassembled my OS 81a after about 30 flights in my U-Can-Do 46. I previously had installed a breather and a cam oiling nipple as shown in my post #20 at http://www.rcuniverse.com/forum/m_80...tm.htm#9161332 I was curious as to the amount of carbon that had accumulated in the combustion chamber compared to the previously installed OS 70 FS with a similar amount of flights. I was also curious about how much oil was in the valve cover as the engine is inverted. What I found was that the carbon accumulation was about identical to the 70 as was the amount of oil in the valve cover.
I had expected to find an increase in both areas for the 81 since all the oil is passing thru the valve cover and the cylinder. There is never any oil discharge from my breather port. I also found that the interior of the engine was immaculate.

I do notice an increase in the amount of exhaust smoke compared to the 70, particularly when opening the throttle after idling during descending manoevers. The engine is one of the smoothest and most reliable singles I have flown.

It seems I’m a bit late to the party here. I see that OS released an updated FS-72α called the 72IIα with BLACK valve covers. They are also now using a nipple on the engine backplate to vent excess oil. The beauty of the Alpha was that they all recirculated spent oil internally back into the combustion cycle, thus making for a very clean and efficient setup.

With the BLACK valve cover 72IIα having a nipple on the back for oil venting, it seems OS is going backwards.

Does anyone know WHY OS did this? Were there any problems with the BLUE valve cover version of the OS FS-72α?

I’m looking at replacing an old OS 70 Surpass II and wanted to use a 72α as it is supposed to be cleaner, but not sure why the change was made to the ‘second-gen’ FS72α.