Looking for a 4 stroke for this plane, whats your vote? [link]http://aero-works.net/store/detail.aspx?ID=75[/link]
Its got a 60 inch wing span and weighs about 5.5 to 6 lbs. If you know another good engine that should be on the poll let me know. I don't know too many 4 stroke engine brands. And if you're wondering why OS is not on the poll its because they're too expensive.

You can't go wrong with the Saito's. I would opt for the smaller one, the 91, as you just don't need the 100 on that size plane. I can hang my Venture 60 on the prop with the 91, it has that much power with a 14x6 MAS. The 100 you would never get over 3/4 throttle, unless you were testing the glue joints. Have fun with that, you should love it.

The Magnum XL .70 RFS, Saito .72, and the Thunder Tiger F-75s four strokes would also be good choices for this model. I believe most 4-strokes in the .91-size category would be heavy enough to make balancing the plane a challenge. A good .70-class 4-stroke tuned and propped correctly should provide more than enough power to punch out straight up from a hover given the plane's all up weight of 5.5 to 6.0 lbs.

If the price of most O.S. 4-strokes frightens you, consider that this model would be a good fit for the affordable FL-70 as well.

Every time someone at my field has a problem with their engine, I try to learn from it what I can. I always ask what brand engine it is. I have NEVER seen someone struggling with an OS. I only have OS 2 strokes, and they start on the first, MAYBE second flip of a chicken stick EVERY time. I believe you get what you pay for, and you can always do 3Pay on tower to help defray the costs.

The Magnum's I've seen at our field tend to be problematic.

Saito is as good if not better than OS when it comes to four strokes. My field instructors swear by the Saito.

The Saito's are great, very easy to tune too.

I've never have had problems with the Magnum four strokers either, but the needles seem to be a bit more sensitive, so it becomes a bit harder to find the operating range...

I have a 60 size PT-19 ,with a saito .80 in it. flys great. I only own saito 4 cycles and have never had a problem with any of them. I take that back I have a OS 1.6 four stroke that I have not run yet. The only thing I have had to do with my saitos is adj. the valve clearence during break in and once after break in. I am sure there are many good 4 strokes out there . I'm just a saito kind of guy.........

So who out there messed with the Magnum .91, I want to find out their pro's and con's. Obviously one pro is the price, but I don't want to buy this engine if its worth spending a little more on a Saito .91. Also on tower they show two different OS .91 engines, one with a pump and one without the pump, whats the difference and whats the pump for?

Out of the engines you posted the Saito 100. It isn't going to hurt the plane and you will have A more usefull engine down the line. Magnums lack the power but not A real big deal, what they really lack is quality and they tend to wear out very fast. Ask yourself why they are only half the price of A name brand engine. The pumps on an OS are just that, A fuel pump. If you are going to spring for an OS the pumpers are always A good idea, you can mount your fuel tank anyplace in the plane without any fuel problems. Most people mount the fuel tanks right over the CG dead center.
I have A couple of all engines mentioned but my number one engines are the YS brand. Before you go to A four stroke you should check out what is the number one four stroke at your clubs, how many people do you know using them, it's A good idea to have someone close at hand to help you out with questions and to show you how to do things that is really using the same engine you buy.

this is great advice. I was interested in getting a YS four stroke, but no one at my club has experience with them, and I would have a bear of a time trying to get one running properly myself. see what's at your club and what's running well, and who's got them running well. If you get the same brand you've got a much better shot at things going your way.

I keep forgetting you can throw on a 3 blade prop. The 100 turns a prop 1" larger in diameter than the 91, and I didn't think the 100 would have proper clearance for the blades at about 15". The 100 is about only $10 or so more than the 91, but you will have to learn very early on what throttle management is. That thing will be a rocket, if you ever punch it on take off , you will flip it over on it's side.

I bought a Magnum 91 for my Model Tech Dragon Lady and after brake in on
the ground ( 1 gallon of fuel) it seemed to run OK but when I took it to the field
for it's maiden couldn't get the darn thing to idle under 5200 RPM, way too high.
Had my original flight instructor test fly the plane for me and almost had a disaster
on it's first flight. Sent the engine back to Global and they replaced the cam, and
that took 2 1/2 months to get it back. Took for it's second flight, same things were
happening, wouldn't idle down and didn't have much power. Had our club resident 4-stroke
guru attempt to do some adjusting and even he couldn't get it any better, suggested it
be sent back again.

I broke the engine inusing 10% nitro with a combination of MAS 14-6 and Zinger 14-6
wood props.Finally sent it back to Global for second time and they said they would replace
the engine but opted for 90 2-stroke instead of the 4 stroke.

Just about everone at our field run either Saito (#1) or OS (#2) when it come to 4-stroke engines.

Flip it?? Rocket??? You must be getting more powerful four strokes then we get here?? Yesterday at the field one of the guys was flying that plane with an OS 1.08 and it was perfect for hard stunting. The guy let my 13 year old student fly it without any problems. The plane is A very nice flying machine too.

A guy at our field had a problem with the Mag. 70. They fixed it but he had to send it in. I don't think they are as powerfull as Saito from what I have seen. If you have the bucks I would go with another engine than the Mag.

You CAN go wrong with Saitos, every once in awhile someone (me) gets one that shakes like hell and you will pull your hair out trying to get it to smooth out. My Saito 1.00 shakes so bad it is destroying the electronics and the plane its self. Have not found a way to fix the shaking yet. Beware.

I was reading the overview on Horizon Hobby for the Saito 1.00. I read something that reminded me about what you said about your engine shaking so badly. But here's what the overview said, not sure if you tried any of this: And it also said this: So maybe you're not running a high enough nitro %.

I have put the OS "F" plug in the engine, no change. I did break it in with 30% and flew it with 30% for a gallon or two but didn't see much if any difference. Trouble is that 30% is so expensive. But I'm going to the hobby shop tomorrow, I might buy another gallon and give it a try. The engine runs great right now, nice slow smooth idle, smooth transition, about 10k top end. All is fine except for the wicked shaking about about 5200 rpm. Even when clamped down hard on the test bench you can see "two muffler ends" at that rpm. Thanks for the suggestion tho, I'm trying most everything suggested. Just adjusted the valves (3rd time) for a tighter fit, tried a heavy Higley prop nut for more mass, different prop (upteenth time) different fuel (four stroke) and a couple of other small things.

New bearings on order. New bearings in a new engine... sigh.