I read about 1000 posts on UCD's and what engines are flying them. I figure for my style of flying I want a 4-stroke and that a YS 61, Saito 72 to 100 or an OS 70 to 91 Surpass will do the job. The data I have seen shows they all weigh within a few ounces of each other. My number 1 objective is to get an engine that is easy to start and run and has ok durability. I would pay the extra money for the YS if it is easier to start and run, but not if its a little more hassle but more pwerful than say the Saito. Most of the local fliers won't think of anything but OS 2-strokes. One of my gurus loves Saitos. The other says they are junk 'cause his only one broke rods twice. He will have nothing but YS. What do you think? I want minimum hassle.

If it's under 5.5 lbs saito 72. If it's over saito 91, both are easy to tune no fuss engines that run great

I have a saito 91 in my ucd and its the best thing I could have done for it. It has unlimited verticle and will pull out of a hover and excelerate on the way up...I had a os 70 in it when I first put it together and it flew nice but the 70 was just not enough. Im also using a apc 16x8 with the saito

I just checked availability of YS63's and Central Hobby says they are sold out. Same story from the wholesaler. I think I will go with the Saito 91.

I have omitted all the unecessary "junk" from the UCD (cowl, pants, spinner, all those ugly monokote color splashes, and decals - basically anything that adds weight that does not help if fly!) , I used lithium Ion power and a micro servo for throttle, and hand-made some carbon fiber landing gear. I also converted to rudder pull-pull since there was more room with a mini throttle servo (got a LOT more rudder throw!). Weighs in at 4.5 pounds. UNLIMITED vertical with a Saito 72 on 15% Nitro.

Of all the .70 sized 4-strokes, I think the saito is the best. In fact, when I was into glow, I canned all my OS engines and ran only Saito (YS for pattern).

I can make the UCD dance up and down in a torque roll at will, so there is no shortage of power with that engine! They key is to build it as light as possible. Its already a hideous plane, so why bother putting all the plastic crap on it... to try to make it look good? It won't work! !! just fly it!!

Its gonna scrape the ground now and then any way if you punish it the way its meant to be punished!!

You will be amazed at the tricks you can do when it weighs only 4.5#

DP

Hey Jack Chief Aircraft still has some YS63's in stock. I ordered one today to go on a funtana. Free shipping too.

YS is coming out with an updated version of the 63.

I haven't heard anything about a redesigned 63. What are they changing? How about some details rhd.

Desertpig,
Every time I look into the Saito 72 I think the 91 is the same weight, about the same price and is 45% more horsepower (per the specs). Why would I not want the 91 instead of the 72? .I am really close to ordering.

Then there is the YS63. I thought it was out of stock US wide. Now I learn Chief has them. It seems to need special fuel and I have seen comments about it being touchy to get running right. My favorite guru says YS is the way to go. The other expert says go Saito.

I am looking for easy operation with adequate power/wt and ok durability at this point. A Toyota instead of a Lambogini.

Well, there's always an OS Surpass.91 (with pump) which is handy.
The new and super .71 ultimate with (pump/pressure)
or a Saito .91 without one... or indeed the 1.10, againwithout one.
If a no brainer is needed, go OS.

Everyone's milage varies from engine to engine. I like ys engines because of the pump, power, and the fact that I rarely ever have to touch the needle. It's true that 20/20 will make this engine rock, but I wouldn't call that special fuel. Just get an engine that you think you will like. There will always be a bunch of people out there to talk good and bad about whatever brand.

trailingedge, you just said a mouthful. The last two sentences should be the header line you see everytime you go in the engine section.

Ed M.

My two cents,,, Saito 91 or YS 63. With the 63 and it's pump you can relocate the tank close to the CG. You will have to put some effort in to keeping the plane lighter. I had both and chose the Saito 91. I put all the gear I knew I was going to use and added up all the weights of the plane. It looked like it was going to end up about 6 pounds. That is really about the limit of the 63 for good vertical. I knew I wanted great vertical so mine got the 91. After having to add one ounce to the tail for balance I ended up at 5lb 15 oz. that should be about perfect for me. My 63 ended up on a 40 size profile that weighs 4lb 7 oz. I did put the Perry oscillating pump on the 91 and moved the tank back close to the CG. Actually I had an old nalgene bottle I used that just fit perfect. I couldn't find a decent sized tank that would fit. Mine holds 12 oz. Both my Saito 91 and YS 63 run great on regular Powermaster 15% castor/synthetic blend.
Good Luck,,,basmntdweller

I think Ohio Model Planes also has some YS 63s in stock.

One more thing. What is the weight of the Saito 72 and 91 with muffler? It seems I find various numbers. I guess because some quote weight w/o muffler and others with muffler but don't say. I got 16.7 oz for the 72 and 18.3 oz for the 91 w/o muffler - I think.

Jack....
May have got this wrong but the saito .91 seems to realise 33.33333333333...% more power than the .72.. ? Regards. Dave

I have a OS surpass II without a pump, runs great and starts easy and had unlimited verticle, I used HS 605s and the planes balanced tail heavy so the OS was the best choice.