I posted this on the fly fly forum also but, I'm about ready to start on my secong 4 Star 40. I had a OS 46 SF on the last one and it flew nice and had decent speed. Thinking of going the 4 stroke route. So I'm very new to 4 stroke and have only seen 1 fly at my field last summer.So I dont know much about them. Anway, would the 4 Star 40 like a 4 stroke? What advantages or disadvantages will I get if I go with a 4 stroke? Will it still have good speed or will it be some what slower since the 4 strokes turn less rpm. If I do go with a 4 st ,what would be the best size for the 4 star 40 and which one? Will I have to get a on board glow system? The one I saw fly last summer did. Thats why I'm asking. Thanks for answering all my questions in advance. I come on here before I try something new. Free advice is priceless. Thanks, JT


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12-17-2002 5:06 PM

Some good choices for a 4 stroke.

Saito 56 for normal overall good flight.

Saito 72 for all out crazy

Magnum 61

O.S. 54

YS - not really sure what size they offer now.

Advantages or disadvantages are very much a matter of opinion, less annoying sound , a little less mess, the Saito 56 will do a little more run time on same amount of fuel and perform pretty close in this particular aircraft. Sense the 4* is really not made for speed you should be able to get about the same speed using a higher pitch prop .

Because of the RPM differences there is really no way to compare which is better, its a matter of what the pilot wants. Comparing the two is almost apples and oranges.

IMO it would be worth it to use a 4 stroke simply because of sound and mess, but if the 46sf is working o.k. why fix it.

Nothin' against four strokes but it is interesting to note that two strokes (gasoline) are widely used at TOC...........

I think a 50cc twin would be just about right for a 4 star .40 . :stupid:

That's only because no one has come out with a good running gasoline burning and powerful four-stroke, Rajul!

Our club has gone 4st crazy the past couple of years. I have a Magnum 80 ( soon to replace a 2st .61 in a Tiger 60) and a Thundertiger .91 which is in a Sig 4star 60. There is a big difference in fuel consumption compared to the 2st. But I also have a SuperSportster 40 which has a Thundertiger pro46, and resist going 4st in it. (this is a similar plane to your 4star 40) I personally like the higher RPM and quicker response of a 2 stroke in this size. But some of those smaller 4 strokes are tempting. Good luck!!!!!

JT,

A four stroke will throw a bigger prop than a 2 stroke allowing more thrust to be produced. A 65/70 four stroke would be plenty of powe plus some for your 4-star 40. As I let you know already my saito 65 pulled the GP Venus arf with authority. I was able to go right into knife edge from take off without any problems. I believe the venus weights more than the 4-star also. The 65 would be just right.l

Rich

Aaaahh ! So, it's a question of availability...........

It won't win the race, but it will dance divinely.

Quote:

"Aaaahh ! So, it's a question of availability..........."

Not available because they aren't practical. You don't see two stroke gassers powering certfied 8 place full size planes either !

A small 4 stroke gasser would sacrifice :

1) Power, Methanol fueled engines have higher output than gassers.

2) Cool running , Gasoline burns hotter.

3) Weight, The addition of a spark ignition system would add considerable weight and take up space not always plentiful in smaller planes.

The big gassers fly great. We have the engines for them because they are practical.
Sport flyers have a broad range of fine four strokes to choose from. We are very lucky ,they came just in time to save many fields we may well have lost due to the objectionable sound of the two strokes.
Are they worth it ? the percentage of four stroke flyers is growing constantly. Many people now fly four stroke ONLY !

More power to 'em

I got to coment on that 50cc gasser for a 4*40. That is the equivalant of a 3 cu. in. engine where a .40 is the size recomended. Another thing is the TOC poeple don't fly anything as small as a 4*40. thats why they use such large engines.[gassers]

Daggonit....I keep coming back after 10 and nothing changes.

LOL ! Anyway, Merry X'mas everybody !

JT
I have heard that the 4st requires some periodic adjustment of
the valve train as it is a solid lift valve train. How simple or complicated the adjustments are I have no idea as they probably
vary from manufacture to manufacture. In an automobile engine
that has solid lift valve train the valves would generally need adjustment once a year @ 20,000 mi. per year. The automobile engine rarely see's RPM in excess off 5000 RPM. If it did it would require more frequent intervals of valve train adjustment. I'm thinking about going 4st myself but until these questions are answered I'll stick with what I have. though the 4st sounds so awsome. Just food for thought.

....The answer to your question...for the 4*40 is the
Magnum .60 4-stroke.

Dave.

If you set the lash after the first hour it will be a long time before it is needed again. I check them about twice a year but very rarely is another adjustment needed.

Thanks for all your replys. I've decided to go with the Saito 56 for the 4 Star 40 . It will be here Monday. I guess go ahead and run the Cool Power 10% in it that I still have left over. Some of you on another thread said it would be fine. I was alittle concerned that Cool Power is only 17% lube and Saito says to use 20% lube in their engines. Thanks ,JT

I have an old .46 enya 4stroke (which is a 52 now days) on my 4 star 40, and I love it, I'm turning a 12-6 prop on it. works great, I have several 4 strokes and I run 15% 2 stroke fuel in them, 2 stroke fuel has more oil than 4 stroke fuel, it works fine for me. and I can use one fuel to fly everything, good luck

You will be more than happy with the performance of your 4st 40 with the Saito 56 installed . A 12x6 prop does a good job for starters

Fuel is another thread in and of itself, but here's some information that might be useful to dispel some myths:

1. "4-Stroke" fuel is not for ALL 4-stroke engines. It is a special blend for older 4-stroke engines that required less oil. Most of today's 4-stroke engines are designed to run with regular glow fuel.
2. You can doctor your fuel mixture by adding oil. It's a simple math problem to figure out how much. Most hobby shops stock a few quarts of Sig castor oil, so if your engine can handle castor, add some to make your fuel match the manufacturer's specifications.
3. Always follow the manufacturer's recommendations for fuel. That way, if the engine fails during the warranty period, you can't give the distributor a reason to deny your warranty claim.
4. Unless the manufacturer says to use a specific "special" blend of fuel, always use regular fuel. Regular fuel is fuel that is marked with the nitro content only. It won't say "4-Stroke," "Heli," or "YS 20/20."
5. All fuels are made from the same materials: Methanol, nitromethane, and oil. The only differences between the various types of fuel are the type and percentage of oil, and the amount of nitromethane. The most important of these is the oil content. If the fuel has the right amount of the right kind(s) of oil, you're generally pretty safe.

As technology advances I think you may see gasoline 4-strokes commonplace on big RC planes. Ryobi makes a 26cc 4-cycle gas engine that Jagengines is currently finishing up the conversion for. It has an oilsump that supposedly works fine inverted. Time will tell. What do you think?

I have read in an engine review or two to take the rocker arm covers off and put a blob of some kind of grease in the covers for the extra bit of lubrication it will give you.I have been doing that for all of my four strokes for a while.I can't say that it has helped,but I can say it has'nt hurt.I have always used lithium grease.Hope this helps you.

You will be happy with the Saito 56. It is pretty simple to run and adjust the valves the first time. After that you won't need to mess with it too often, if ever. I flew two strokes for many years and the Saito 56 was my first four stroke. Now I have six four strokes and other than the higher price I prefer four strokes. Well except for really fast planes, where only two strokes will do.