brett65

My Feedback: (18)

I'm gonna try and mount the new OS 70 on a plane and fire her up. Anything special to do? I got 15% wildcat fuel that I use in the 2 strokers. Gonna read the manual completely tonight. What size prop would be good to put a tank through her with? I got a 10x5 3 blade, would that work? I know everything about a small block ford V8, but this little thing intimidates me!

MetallicaJunkie

I would run a couple of tanks on the ground first. I use 15% fuel as well. Ive run several props on my 70, right now i have one flight on a 12x8 mas, so far i like it. Ive also used a 12x7 apc which was great too , and an 11x10 for speed. I think he 10x5 3 blade might be small, but i could be wrong. I wouldnt run higher than 10k rpm on a 4 stroke

Mikecam

I just maiden a Cub with a OS 70 SII. For sure run some tanks thru her on the ground and then tune the low end before flying. Mine was way rich from factory as expected. What wasn't expected was having to run the idle so high to keep her running. Took three tries to slow the Cub down to land. Tune the low end and then richin it up a little before first flight. Mine ran very good after tuning the low end and now at idle she just ticks away. Sometimes its hard to tell she 's still running. I've left mine to idle for 2 minutes and she still rockets to full throttle with no hesitation. I used a APC 12x7 Good luck

jimmyjames213

My Feedback: (2)

heres a few
dont over rev a 4 stroke (aka prop it correctly) the valves will "float" and hit the piston resulting in a new engine comming in the mail from tower
4 strokes can chuck the prop when they are too lean (causeing a backfire), dont stand in front of the engine during tuneing and always double nut it.
set 4 strokes slightly richer than 2 strokes they have more moving parts

as for props try a 13x6

plan on checking the valve clearence after 5ish tanks

redfox435cat

run a least 2 tanks on the ground. Run it sloppy rich for a few seconds then peak the rpm with the needle for 10-15 seconds. richen it a full turn, run it for a few seconds then lean it to peak, do this for two tanks. The next two tanks fly it a little under a half turn rich.

MinnFlyer

My Feedback: (4)

I do like redfox suggested, but for only one tank. Then fly it a little on the rich side for a flight or two. Then let 'er rip.

One thing to note... 4-strokes DO NOT like to run lean!

As for prop, I use a Graupner 12x7 for break in and flying

FILE IFR

4 strokers smile and run well with a heavy weight prop like a Graupner. Light weight props like a Master Airscrew and wood ones are undesirable.

brett65

My Feedback: (18)

I noticed that the throttle arm is on the opposite side that it shows in the manual. Can the carb be flipped to wherever it fits the plane best? It looks easy enough from what I can tell.

Gray Beard

My Feedback: (-1)

BS!!!! Everyone that knows anything would be running a 13X6 APC but you must, and this is a very important must!! You must soak several 13X6 APCs in Ritt Dye to match your plane!!! They run much better with a color matched prop!!
What a bunch of silly people!! Everyone knows this!![8D]

MetallicaJunkie

yes you can switch it around with no problem

Campgems

Yep, turn the carb to where it fits best. Two thing to consider, throttle linkage and access to the needles. It's kind of a pain to get to the mix needle from the bottom, but what ever works for the aplication and the individual plane is good.

Four strokes run best with the head up, and the head to the side. Inverted is ok, but it needs to be realy warmed up before flying. I've got an O.S 52 in a Pheonix Fun Star and it is mounted with the head at 4:30 looking from the front. The engine runs just awful for a few minutes on the first run of the day. After it is warmed up well, it runs like a champ. I found that the rocker cover collected a huge load of oil that drained down from the cam area. When it was fully heated up and spun into a mist, all was good, but the first run of the day with the puddle was ugly for a few minutes.

Tune the engines when they are warmed up. Learn to tune the four stroke. They respond a bit different than a two stroke. The like big props for their size, and they like heavy props. My choice is the APC props and I kind of buck the advise of others here, if the plane will handle slow speed, use a low pitch prop. The 70 will crank a APC 13W with athority and it will let you go as slow as the wings will allow. When you need to punch it to get out of trouble, it will respond. Right now.

Put an armed guard on your wallet and check book. They are adicting. I've currently got 9 of the four strokes and love them all.

Don

brett65

My Feedback: (18)

I would try that except a color matching 3 blade on an FW-190 might look silly unless it was a racer. hmm....

HighPlains

My Feedback: (1)

Get a good tach, and use it to set the needle. 300 down from peak seems to be typical, but your mileage may vary.

GaryHarris

Brett, once you go 4-Stroke, you wont go back!

MinnFlyer

My Feedback: (4)

Try tuning it by ear before buying a tach. Some guys can't tune a 4-stroke without one, but nobody I know needs it

Gray Beard

My Feedback: (-1)

No Ritt Dye?? It will never run!!!!
Mike, I bet you I have one that every one you know would need a tach with!!!! I finally had to pull out my tach to get it correct. Hurt the heck out of my ego too!!! I guess better the ego then all the dead sticks though.

MinnFlyer

My Feedback: (4)

Nope, never met a 4-stroke i didn't like

ChuckW

It sounds like you have plenty of experience on cars and other types of engines. You'll do just fine. Just be sure it doesn't get too lean. It will let you know by knocking, detonating and possibly spitting the prop if you do. Get it dialed in and have fun.

Gray Beard

My Feedback: (-1)

My old YS 1.20 NC would give you fits!!! The low end adjusts with the regulator screw and by ear there is no way you can hear the RPM rise, it is running one second and goes lean the next click, you can turn the high end needle over a half a turn and hear nothing. I pulled out the tach and was finally able to see the rise and fall of the RPMs. This is the first one that I have ever had that is like that but it beat my mule. Runs beyond great once you find that sweet spot but finding it is a mystery without a good tach. It's my mystery engine!!

JOHNS3D

My Feedback: (5)

Brett a breaking-in is a key of a good 4 strokes engine. First follow the manual...run it rich by one turn...then close the needle to get max rpms for 10 seconds and then open again one turn...do it for 2 tanks. Its important to let the engine run rich to cool it down.

After a few tanks...run it rich for 10 flights. Start to close after that....most of the people is 500-800 rpms under from the max in this period to avoid any overheat.

Regards,

safeTwire

My Feedback: (2)

With regard to installing the prop...

First...Tighten the prop to the engine completely using ONLY the Prop Nut.

Second...secure the Prop Nut in place by holding it, then tightening the Lock Nut against the Prop Nut.

When tightening, keep in mind that the intended "target" of the lock nut is... the Prop Nut! Of course the final result will be a secure propeller!

It is a Two Step Process!

I suggest correct sized "combination" wrenches (open end on one end and box end on the other) as opposed to adjustable wrenches for 4 stroke prop installation.

bigtim

My Feedback: (13)

(quote)FILE IFR
4 strokers smile and run well with a heavy weight prop like a Graupner. Light weight props like a Master Airscrew and wood ones are undesirable.
NO!
MAS props work great on any engine including FStrokes and wood as well, if your flying a tail dragger then MAS props are durrable and can survive prop strikes, wood on the other hand are toothpicks in the making whenever they touch the ground

(quote)MinnFlyer
Try tuning it by ear before buying a tach. Some guys can't tune a 4-stroke without one, but nobody I know needs it.

if its your first 4stroke, get the tach it makes tuning much easyer for the first timer, once you have heard the sound of the engine changing rpm( there is little if no engine sound change frankly) then the choice is yours, its easy to get a lean run thinking your needle is set right, when the engine is on the lean side, I always use my tach on the first run of the day to set the needle after that its fuel and go.
on my 91 and 120 OS FS engines I get about 9,800 top RPM's back that off 300-500RPM as you richen it for flight, you will get those RPM's as the engine unloads in the air durring flight, if your running top RPM's then when the engine unloads you can get the floating like posted earlier,better to run a bit rich than run to the repair shop.

I use Coolpower 10% and they run well also

GaryHarris

And MAS props makes a 4 stroke specific prop called the "K Series". I don't know what that means though.

bigtim

My Feedback: (13)

not sure either, but here's a 2 and 3 blade MAS K series props on OS91's, for them I use the 14/6 to8 2 blade or 14/6 3 blade depending on the pull I want, both have survived several strikes with minimal dammage, the P-40 in particular is a real tipper it ends up on its spinner if I am not carefull on landing, I now use a 14/8 2blade on it.

redfox435cat

all I've ever used is mas k series props for my 4-strokes, the k series prop are fatter(wider blade than standard props, they better utilize the torque. The exception is my gee bee, I an apc for top end speed. With the MAS lightness I'll usually just used a bigger prop when I can, scale and pattern applications, they idle better with a big prop.