wannabflyboy

My Feedback: (10)

I'm running a OS FX .61 on my sport plane currently but I'd like to go 4 stroke. Can anyone recommend a motor that will give me more vertical without going off the charts?

nexxa

OS .75 AX or OS.91FX... much more power and practically same engine weight 19oz. Same bolt pattern for all three.

.75 on a 14X4, 13X5, 12X6 work great. My favorite is on that engine APC 14X4 Wide or 12x6. Other prop suggest by OS just load the engine too much, out of engine power range.

Just my two cents...

Jetdesign

My Feedback: (8)

Saito 100. I'm an OS two stroke guy, but my next four stroke will be a Saito; great reliability, power to weight ratio.

wannabflyboy

My Feedback: (10)

So are you saying the Saito 100 definately pulls harder than the .61FX? Most of the 4 strokes don't list power ratings so it makes it hard to judge. I understand the torque curve is completely different between 2 and 4 strokes, but just the same it's hard to come up with a comparison.

Jetdesign

My Feedback: (8)

I don't have experience yet withe the Saito four strokes. However, a .46 two stroke would be about a .70 four stroke, a .90 two stroke about a .120 four stroke, so I figure the 100 would be in the same power range as the .61. Four strokes give more power at low end though, so even if it's not more power, you can use a larger prop and get more pull and better climb.

Hopefully you'll get some more answers from people who've used these engines, but I'd say a 100 or a 115 would be right around what you're looking for 'without going off the charts'.

I'm considering a Saito 125 on a 9lb plane and a .90 two stroke would probably leave more to be desired, but videos of the 125 show very good vertical performance. So you shouldn't need a 125.

ChuckW

First off, ignore any listed power ratings that you see. There are so many variable behind them that they are almost useless.

The 4-stroke will generally have a lot more low-end torque giving it the capability of swinging a more agressive prop (larger diameter or higher pitch or both)

A 4-stroke replacement for you .61 should be in the .90 range. Something like an OS .91FS, Saito .91, etc. Saito also makes the 1.00 which is pretty much a bored/stroked .91. I hear Saito is coming out with a 1.15 in the same size & weight range too. OS is releasing a 1.10 as well. While I have not tried them but I know Thunder Tiger makes a .90 class 4-stroke. Then there is Magnum and YS.

What kind of plane do you have? You can pretty much figure out a 2-stroke or 4-stroke to do what you want.

I'm a big fan of the OS .91FS. It is just as user friendly as their 2-stroke engines in my opinion, ultra reliable and has good power. I've personally found that the Saitos are a little more finiky when new (maybe just my perception) but they run so sweet once they are broken in and tuned well.

I say go for the 4-stroke. No matter which you choose, the sound, the fuel economy, the torque and all the other stuff is very cool in my opinion.

JohnBuckner

My Feedback: (1)

The FX 61 is a wonderful engine that becomes an awesome engine with one of these for seventy bucks:

http://www.pspec.com/details.asp?ProdID=61&category=8

A lot less money bankable performance with a true quarterwave pipe (with the internal tract to perform the magic) and a whole bunch cheaper, far less work and saving the best for the last a far better sound that is totally unique from a true resonent pipe much different than the muffled two stroke and much better the the fourstroke.

John

JohnW

My Feedback: (6)

Prop selection can make a huge difference in your vertical. I know this was touched on in one of the above posts, but I'd like to point it out again to be sure it wasn't lost. Hard to go wrong with any of the major brands of 4 stokes as posted here. I’d also consider piping the engine you have now as John B. suggested.

tunes079

A comparable 4-stroke would be a .91. I redomend the saito, but i'm biased. I just love em.

carrellh

For $7.95 you could try an APC 13x4W prop on your existing engine
http://www.apcprop.com/cgi-bin/store...1236&ppinc=apc

If the "wide blade" is too much load for the engine you could try a 13x4 Sport prop for $4.89
http://www.apcprop.com/cgi-bin/store...1235&ppinc=apc

One of each, plus shipping, would be a pretty cheap experiment.

Or, spend the bucks to get a 1.00 to 1.25 cubic inch Saito four stroke.

wannabflyboy

My Feedback: (10)

The tuned pipe sounds like a possible alternative for now. I'd love to hear from anyone that's used one. The only thing I'm not crazy about is the size: 8 inches long for my 61. Could have fuselage clearance problems since I mounted the motor sideways but I'll look into iy. Thanks for the suggestion.