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O.S. GF40 4st gas

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Old 05-12-2013, 05:38 PM
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MKnutson
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Default O.S. GF40 4st gas

Has anyone tried one of these yet?
I've got one on the way, (yes I know it was alot of coin), but it IS an OS after all.
I'm installing it on a GP Giant Super Sportster for some nice laid back cruiser flying.

Mark.
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Old 05-12-2013, 05:50 PM
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Default RE: O.S. GF40 4st gas

Oh please keep us posted. Very interested. I've had only good experiences with their 2 stroke gassers. Saito gas has been less than steller, unfortunately.
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Old 05-12-2013, 06:12 PM
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Default RE: O.S. GF40 4st gas

Would love to see how it powers that airplane. I built a fellow club members super sportster with a dle35 and it is way over powered and I am interested in this engine for a ESM corsair.
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Old 05-12-2013, 07:33 PM
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Default RE: O.S. GF40 4st gas

I also have the Saito FG-57T gas twin, and am not totally impressed with the design quality. The cams run almost dry, very little lube gets up there so I oil them after every flying session.
That is why I liked the particular design of the OS, the way the oil blowby mist is circulated thruogh the engine and up through the rockers then into the intake.
I will keep you all posted how it runs and flies the super sportster. I'll try and get some numbers with different props.

Mark.
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Old 05-15-2013, 03:13 PM
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Default RE: O.S. GF40 4st gas

The brown truck stopped by and had the engine!
First off I can say it looks typical OS perfect casting, and it's a little lighter than my NGH38.
Overall a very nice looking engine.
It has unbelievable compression just out of the box.
A decent baffled muffler comes with it, which is good for our field.
Only a couple of gripes that I can see are (1), it comes with an RCexl made in china plug, cm-6 type.
And (2), the prop shaft is a little small for this size engine, I have to make an adapter bushing to fit any of the props that this engine will use.
These size props all come with a 10mm hole and the shaft threads are 5/16 or appox. 8mm.
Other than those two small issues, she's a sweet engine!

Mark.
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Old 05-15-2013, 03:33 PM
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Default RE: O.S. GF40 4st gas

When do you propose to have it running?
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Old 05-15-2013, 04:34 PM
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Default RE: O.S. GF40 4st gas


ORIGINAL: MKnutson

I also have the Saito FG-57T gas twin, and am not totally impressed with the design quality. The cams run almost dry, very little lube gets up there so I oil them after every flying session.
That is why I liked the particular design of the OS, the way the oil blowby mist is circulated thruogh the engine and up through the rockers then into the intake.
I will keep you all posted how it runs and flies the super sportster. I'll try and get some numbers with different props.

Mark.
You can do the same thing to your FG57 W/some check valves.

You will have to dismantle the engine to drill & tap a breather nipple in the case between the cams.

Then, use an inlet only check in the rear breather & an outlet only check inbetween the cams.

The FA300TTDP was set up that way to pressureize the gas tank to feed the dual carbs that are mounted high above the fuel tank cenerline.



The breather air will enter through the rear check valve & be forced to the area between the cam housings.

You could also probably put breather nipples in the exhaust rocker covers & run lines from them to a "T" & then to an inline check valve in the outlet line.
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Old 05-15-2013, 07:28 PM
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Default RE: O.S. GF40 4st gas

I'lll have it running VERY soon. I had to make the prop shaft adapters down at work, but it will be running soon.
I know this was alot of money, but, after fondleing it for a bit I think it's going to be worth it.
MUCH better design than the Saito, of which I've had or have quite a few.
I don't think anyone will be dissappionted with this.

Mark.
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Old 05-15-2013, 07:32 PM
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Default RE: O.S. GF40 4st gas

I'm hoping this engine works out great, with no fiddley attributes. also want to pick one up! Keep us informed
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Old 05-15-2013, 11:01 PM
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Default RE: O.S. GF40 4st gas

Anyone have a link to this new 4-stroke OS engine?
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Old 05-16-2013, 09:04 PM
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Default RE: O.S. GF40 4st gas

I got it all mounted up to the test stand and ran it this evening.
The idle mixture screw was way too rich, so I leaned it up a bit then it finally started up then we went in a little more to get the idle to smooth out.
With just 5 mins running on 20:1 mix it turned some pretty good numbers, once loosened up and a leaner oil ratio gets run through it it will get even better!
Once I get it on the plane I can really tweak the needles like it needs. Transition is ultra quick from idle to full back to idle again.
We tried a hand full of props to get some figures, all props are Xoar laminated but one Mejlik carbon.

Mejlik 18-10 8200rpm/1600idle
Xoar 18-8 7900 1700
19-8 7400 1700
19-10 6700 1700
20-6 7500 1700
Keep in mind these will get better with more time and less oil in the fuel, but for now these look pretty good to me.
This engine runs very smooth and tight, very OS like. Also, the muffler actually works, it sounds like a goood running OS 120 surpass!

It's a KEEPER!


Mark.

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Old 05-16-2013, 09:07 PM
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Default RE: O.S. GF40 4st gas

Ernie,
Tower has them on their web site, and in stock too.

Mark
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Old 05-20-2013, 09:13 PM
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Default RE: O.S. GF40 4st gas

Iv'e been flying it on my new Giant super sportster and it's getting better every flight!
About 10-15 flights so far and it pulls like crazy! 19-8 Xoar laminated is what it seems to like so far.
Running Klotz kl-100 synthetic oil at 32-1 so it still smells like a model plane.
It runs very smooth, doesn't shake the crap out of the ailerons or tail at idle, plus it's quiet!
Everyone that sees it at the field wants one.

Mark
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Old 05-21-2013, 12:20 PM
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Default RE: O.S. GF40 4st gas


ORIGINAL: MKnutson

The brown truck stopped by and had the engine!
First off I can say it looks typical OS perfect casting, and it's a little lighter than my NGH38.
Overall a very nice looking engine.
It has unbelievable compression just out of the box.
A decent baffled muffler comes with it, which is good for our field.
Only a couple of gripes that I can see are (1), it comes with an RCexl made in china plug, cm-6 type.
And (2), the prop shaft is a little small for this size engine, I have to make an adapter bushing to fit any of the props that this engine will use.
These size props all come with a 10mm hole and the shaft threads are 5/16 or appox. 8mm.
Other than those two small issues, she's a sweet engine!

Mark.
Sounds like the engine uses the standard 8mm shaft size, same as on their 33cc 2 stroke. APC has that hub size standard on their props. APC has recentlyreleased several props intended for the YS170 and 175 glow alky engines. These should work well on the OS40cc, (I think)
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Old 05-21-2013, 12:54 PM
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Default RE: O.S. GF40 4st gas

Mark, Outstanding! Very glad to hear of great running qualities for this new four stroke, any chance for a vid?
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Old 05-21-2013, 05:52 PM
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Default RE: O.S. GF40 4st gas

What's that sound? Yes, the sound of money leaving my pockets...not sure if that was a good or bad report...but it's making me go broke.

Keep the reports coming.
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Old 05-21-2013, 06:43 PM
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Default RE: O.S. GF40 4st gas

Hey, I figure one good engine is worth at least two China ones.....Right
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Old 05-21-2013, 07:38 PM
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Default RE: O.S. GF40 4st gas

How would you say the power to weight ratio is compared to a similarly powerful 2-stroke?
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Old 05-21-2013, 08:54 PM
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Default RE: O.S. GF40 4st gas

Iv'e got the DLE 35RA rear exhaust also, and it is no slouch in the power dept.
Power to weight, the 4 strokes will never be as good as similar size 2 strokes for all out power.
I wasn't going for sheer power it the choice of this engine, my dle 35 will spin the same prop a bit higher than the OS. I got this engine for the inherent quality of OS and for the 4 stroke sound.
OH, and the "sound", my wallet is a touch thinner from this thing too! I like it enough to possibly get another one.
I could really see this engine residing on the front of a H-9 1/4 PA-18 cuper cub! That would be another perfect combo.

Mark.
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Old 05-24-2013, 12:51 PM
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Default RE: O.S. GF40 4st gas

Mark, you say this engine runs smooth, without much vibration I take, what about the throttle responce? Does it have a linear throttle ? Or the typical walbro on/off switch?
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Old 05-24-2013, 09:31 PM
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Default RE: O.S. GF40 4st gas

The throttle response is very quick, and yes, since it has a walbro it doesn't have a linear throttle.
What I do is use the throttle curve in the transmitter to help linearize the power, it works really well.
I tweaked the high end needle today, and now it rips the 19-8 xoar in level flight on the giant super sportster, and this plane isn't exactly the most clean airframe.
This is turning out to be a real sweet engine!

Mark.
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Old 05-26-2013, 09:06 PM
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Default RE: O.S. GF40 4st gas

ORIGINAL: SkyPilot101

When do you propose to have it running?
Hi everybody who loves OS 4-stroke engines.

I got my GF40 3-4 weeks ago from TowerHobbies and run it on stand (braking in) a week ago for about 1 hour.
Its quite impressed me compare to my SAITO FG-36, buy very quick response and clean running (no extra oil spill vent).
I have run it for the most brakin in time in idle mode and also noticed as it is set a bit rich by manufacture.
Running smooth and stable especially with a bit heavier APC 18x8. With Xoar 18x8 it is also good runing, but static thrust is a bit higher with APC. Regarding vibration do not be fulish by statements above in the posts. Yes, it has some RPM spots, where it is get in resonanse a bit with heavy stand, but as soon as you a bit off by RPM it is running well smooth. I didn't find much difference in vibration between Saito FG-36 sitting on the heavy motor mount and GF40 sitting on 4x 50mm standoffs. Props have been balanced to the perfection before testing.
I'd like to highlight again ... it is very responsive engine, which bring my attension right away. In the manual OS is asking to use throttle accurately avoiding very sharp changing . . . I have tried VERY fast throttle change and engine responced VERY WELL !
This engine is close to 300gr lighter than my SAITO FG-36 thus looks as a very good replacement with more power and less mess from extra oil spill vent on FG-36. The temperature wise looks good to me on idle and close to 4500 RPM on the ground. The lowest Idle I got was close to 1150 RPM with APC 18x8. I think after a few flights it will be very stable at quite low RPM.
Regarding close to 8mm shaft and props => Tower has 18x8 Xoar props with 8mm hole. One thing what I have been missing right away is adapter for the spinner. A bunch of adapters from SAITO FG-36 and FG-21 doesn't fit, thus I ordered one from Tower for the next time as I like to use my ALIGN Starter. Regarding casting I would say my particulr one is a bit rough compare to my 3 SAITO engines, but it is less important thing.
First time I started engine I forgot that engine has a choke. All my SAITO engines doesn't have choke. It is a good addition, which allow to prime engine very fast, although I didn't try it in inverted installation when extra fuel may get into the chamber.
Ignition box is very small, even smaller than I have from Rexel for my FG-36. It is also has quite unique feature not to ignite spark untill it will reach 120RPM. You fingers will be safe rotating prop back and forward by hand !!! My came with Rexel spark plug, which I replaced by very high quality Japanees made one right away. The fuel consumption looks the same as with my SAITO FG-36. The sound is good and mufler is big enough to silent it. Although I didn't run FG-36 and GF40 side by site the sound and noise level looks very similar. I also noticed that 18x8 is easy prop for GF40 although for FG-36 it is just right one. I think to run APC 18x8W, which is equivalnt to 19x9,5 or 20x7,5. I found that APC props better on 4-stroke engines as they a bit heavier and profile is better than Xoar, although Xoar props looks nicer. Also ... I had many hard landings with APC props and never broke them, but Xoar props are very sensitive by toutching soil and they brakes easily.
I am looking forward to run my new engine on my 27% RV-8.
Sorry for my English.
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Old 05-26-2013, 09:17 PM
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Default RE: O.S. GF40 4st gas

Thank you for the nice report and information. Your English is fine - good to hear you are having fun and a positive OS 4-stroke experience!
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Old 05-27-2013, 12:54 PM
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Default RE: O.S. GF40 4st gas

Once you get it leaned out from the stock settings at idle, it will get smoother running. Have you tried running it at full throttle yet since you mentioned youv'e had it up to only 4500 rpm. As far as vibration goes, NO single cylinder engine can be totally balanced perfect. This engine has strong power pulses but it doesn't shake the plane as bad as the DLE 35 at idle. I'll have to try the apc 18-8w and see how it runs.
I don't want to tout this as the be all end all 4stroke gas engine! After comparing the design between this engine and the Saito, which Iv'e got one of, (FG-57T), I liked the OS better. The cams run on bushings and almost totally dry with the Saito. Don't get me wrong, my Saito gas twin runs like a top, and very smooth and sounds cool too.
I don't want this to be a debate beween OS and its competitors. This has been a good ownership experience for me with this, (OS), engine. Compared to the NGH 38 gas 4 stroke that I also have, the OS has been a dream!

Mark.
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Old 05-28-2013, 04:22 AM
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Default RE: O.S. GF40 4st gas


ORIGINAL: MKnutson

Iv'e got the DLE 35RA rear exhaust also, and it is no slouch in the power dept.
Power to weight, the 4 strokes will never be as good as similar size 2 strokes for all out power.
I wasn't going for sheer power it the choice of this engine, my dle 35 will spin the same prop a bit higher than the OS. I got this engine for the inherent quality of OS and for the 4 stroke sound.
OH, and the ''sound'', my wallet is a touch thinner from this thing too! I like it enough to possibly get another one.
I could really see this engine residing on the front of a H-9 1/4 PA-18 cuper cub! That would be another perfect combo.

Mark.
So, thinking of getting one of these for my 88 inch Tiger Moth.
What do you think?
Tiger Moth needs a 4 stroke, just for the sound.
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