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LT-40 Four Stroke Engine

Old 08-11-2008, 06:30 AM
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Supa Koopa
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Default LT-40 Four Stroke Engine

Hi Guys,

I'm going to be starting the build of a Sig LT-40 and would like to put a four stroke engine in to it. I just love the sound of four strokes. I have a choice of three engines a OS FS52 surpass, Saito FA62a, and a os FS 70 surpass II. Now the prices are all very similar as my LHS has a sale on the OS's. I know the right engine for it is the 52, some will say a 46ax two stroke, but ideally I would like to be able to use the engine again on another plane. The 62 and 70 will be of more use than the 52. Am I going to experience major problems with either of the bigger engines? Should I just stick with the 52 and hope to find a plane that it will fit in and work well with.

Any thoughts and info are greatly appreciated.

Craig.
Old 08-11-2008, 07:52 AM
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Fred 1969
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Default RE: LT-40 Four Stroke Engine

I have the 70 surpass on mine. Great engine. Good combination.
Old 08-11-2008, 08:39 AM
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Supa Koopa
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Default RE: LT-40 Four Stroke Engine

Thanks for the response Fred 1969. I read someone else's post on here that they had put the 70 surpass on there's, but had a few issues with balance and slowing it down for landings. Have you experienced any of these issues? You have cheared me up though, as it's the 70 I really want as I know I will have more options in the future.
Old 08-11-2008, 09:08 AM
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Default RE: LT-40 Four Stroke Engine

I just put in a 35 minute flight with my OS 70 on a 13 oz tank in my Four Star 60 - sweet combination. Couldn't believe how long it ran, and I wasn't loafing around.

However, the OS 70 is a heavy engine. A friend's LT-40 balances just fine with a Fox 40, which only weighs 12 oz. That tells me I don't want a 20 oz engine on this plane. The little Fox pulls the plane straight up, but it's a beautiful floater too. He has a ball with that plane, and he is an experienced pilot who has flown much hotter stuff. If it were me, I would buy the Saito 62 for your LT-40 - you'd save a quarter pound in the nose, the stress on the airframe would be less, and I think it would be a "ham and eggs' combo.

The Saito 62 has a great reputation and it will fit "46 size" planes - you will always fine a use for it. Jim
Old 08-11-2008, 09:11 AM
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sawdust
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Default RE: LT-40 Four Stroke Engine

The weight should not be an issue. The 70 is less than an ounce heavier than a 46 AX.

This one of the best planes to teach some one how to land. You just line her up cut the throttle and let it settle to the ground.

Now if you don't hve your 70 tuned to slow idle then slowing down might be an issue.

I have a 70 on a Kadet Senior and a 46 fx on my LT40 ARF. Love both planes

Todd
Old 08-11-2008, 09:18 AM
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jester_s1
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Default RE: LT-40 Four Stroke Engine

Trying to save money has cost a lot of guys their airframes. If you will get the appropriate engine for the plane you are flying now, you will have the best chance of flying it successfully. When it gets time for a second plane, start from scratch there too. Buying an engine that's too big for the plane you are flying now, especially as a beginner, will just increase your chances of crashing. Buying radio gear with thought for the future is a good thing, but putting a too heavy engine on hoping to use it on your second plane is just not good building. A light weight 2 stroke engine is tailor made for a plane like yours and will fly it better than anything else.
Good luck.
Old 08-11-2008, 10:06 AM
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w8ye
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Default RE: LT-40 Four Stroke Engine

I have a OS 52 on my LT40 and it has plenty of power. There were no balance issues. All the radio/battery stuff is in the regular positions. in fact I used to have a Tower 46 in the plane and the OS 52 is bolted into the same holes and the same throttle tube line is used. I've had the plane close to 10 years andit has well over 100 flights on it.

I think that you will never regret having bought a Saito 62 for this plane and future uses. It seems to have as much ower as the OS 70 and weighs a lot less. After all I have 22 Saito engines. I also have four OS 52 four strokes.
Old 08-11-2008, 10:09 AM
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Supa Koopa
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Default RE: LT-40 Four Stroke Engine

Thanks for the help. It would seem I have quite a mixed bag of responses. Jester this is not meant as a cost saving exercise as here in Rip Off Britain we pay a lot more for this stuff. An OS 46AX is around $140, an OS FS52 is $200, Saito 62a $240 and the OS FS70 is $240. This is with finding the cheapest prices around, retail on the Saito is around $300. I have already built a 4*60 with a lovely Saito 82a in it, but have decided I should try a trainer first. I have quite a bit of flying under my belt but this is with Helis, so I am hoping my orientation transfers over. It's just the landings that will be quite a bit different. So my thinking is that if I do go past the trainer quite quickly whatever engine I bought could be used again. Now if I have bought the correct two stroke this will more than likely go the graveyard that is the spares box. I am a bit sick of two strokes from the helis screaming their nuts off all day long, so the four strokes were a bit of a revelation.
I can see what people are saying about the weight issues and this has made me think twice. Weights are OS 46ax 13.3oz, OS 52 15.3oz, Saito 62 16.4oz and the OS 70 20.3oz. I know I should be buying the 46ax but it just sounds like a scooter on steroids.

Decisions, decisions.
Old 08-11-2008, 10:26 AM
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Default RE: LT-40 Four Stroke Engine

Make sure you're including muffler weight when comparing engines. The .46 AX is actually around 17 ounces or so with the sport muffler attached. A .52~.56 four stroke will likely be lighter weight than a .46 AX with muffler.

Too many pilots short change the .52~.56 size four strokes. These are very powerful motors that are every bit as hot as a good ball-bearing .46 two stroke.

A .70~.75 four stroke is really more similar to a .51~.56 two stroke with regard to power output. These engines are great for heavier or high performance "50 Size" airframes, but are complete overkill for an airframe like the Kadet LT-40.

There are a hundred great uses for a .52 four stroke after you decide to take it off of your Kadet LT-40. Don't buy into the notion that you have to have the biggest crank case possible to strap onto the nose of your next plane.

Good luck and good shopping!
Old 08-11-2008, 10:29 AM
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Default RE: LT-40 Four Stroke Engine

That weight for the .46 is without muffler, whereas those 4 stroke weights are with muffler. The .46 with muffler will be up around 17 oz., so it is really comparable to the smaller 4 strokes on your list.

I have recently started using 4 strokes and I enjoy them so much more than a screaming 2 stroke. I actually feel like I fly better when I'm not listening to those high revs, and the 4 stroke sound really enhances the whole experience. You probably save some on fuel too, but that is not the issue - it is the experience we go out to the field for, and the extra for a 4 stroke, given all the other expenses of the hobby, is well worth it to me.

Sawdust - I think we are talking about 2 different 70s - maybe you have the FL, which is about 18 oz w/muffler. I have the original Surpass, which is a little over 20.

Jim
Old 08-11-2008, 12:42 PM
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Default RE: LT-40 Four Stroke Engine

If you are just learning use the 2 stroke because they are more bulletproof for crashing then a 4 stroke.
Old 08-11-2008, 12:46 PM
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Default RE: LT-40 Four Stroke Engine

I think a lot of time and effort is being misplaced in talking about engine weight. With an LT-40, so long as you're in the ballpark you're fine. It's a big airframe with a very generous wing size.

Four-strokes are nice motors. The quality is generally much more even than two-strokes. I don't know of a bad four-stroke on the market right now. The prices are slightly higher. They're really no more difficult to run, just different. A tachometer becomes a necessity, but that also takes the guesswork out of tuning. That may make it easier for a beginner. At any rate, it's a personal choice. It won't greatly impact how the plane flies, but it may impact the level of personal satisfaction involved.
Old 08-11-2008, 01:29 PM
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Default RE: LT-40 Four Stroke Engine


ORIGINAL: Supa Koopa

Thanks for the help. It would seem I have quite a mixed bag of responses. Jester this is not meant as a cost saving exercise as here in Rip Off Britain we pay a lot more for this stuff. An OS 46AX is around $140, an OS FS52 is $200, Saito 62a $240 and the OS FS70 is $240. This is with finding the cheapest prices around, retail on the Saito is around $300. I have already built a 4*60 with a lovely Saito 82a in it, but have decided I should try a trainer first. I have quite a bit of flying under my belt but this is with Helis, so I am hoping my orientation transfers over. It's just the landings that will be quite a bit different. So my thinking is that if I do go past the trainer quite quickly whatever engine I bought could be used again. Now if I have bought the correct two stroke this will more than likely go the graveyard that is the spares box. I am a bit sick of two strokes from the helis screaming their nuts off all day long, so the four strokes were a bit of a revelation.
I can see what people are saying about the weight issues and this has made me think twice. Weights are OS 46ax 13.3oz, OS 52 15.3oz, Saito 62 16.4oz and the OS 70 20.3oz. I know I should be buying the 46ax but it just sounds like a scooter on steroids.

Decisions, decisions.
If it were my decision I would buy the Saito 62
But this is only my opinion.

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