logo
Thread Tools
Old 01-07-2018, 09:38 AM
Fletch88 is offline
Find More Posts by Fletch88
Registered User
United States, GA, Valdosta
Joined May 2017
34 Posts
Discussion
Who's Flying OS GF 40

So I picked up an almost new OS GF 40 for my next possible warbird build. I have read all about the rocker problem one person had which I hope is an isolated occurrence. I use Redline 40:1 in all my other gassers will this be sufficient for this OS 40? Anyone out there love these engines, hate these engines. Any advice appreciated.
Fletch88 is offline Find More Posts by Fletch88
Reply With Quote Quick reply to this message
Sign up now
to remove ads between posts
Old 01-07-2018, 04:30 PM
Fletch88 is offline
Find More Posts by Fletch88
Registered User
United States, GA, Valdosta
Joined May 2017
34 Posts
No one using these? Hello
Fletch88 is offline Find More Posts by Fletch88
Reply With Quote Quick reply to this message
Old 01-08-2018, 11:20 AM
Kiva Flyer is offline
Find More Posts by Kiva Flyer
Registered User
New Mexico
Joined Sep 2007
422 Posts
I bought one in 2014 from Tower and installed it in a 73" AJ Laser. I'm used to hand starting my engines but this one was electric start only, at least for me and my shoulder. It has good, not stunning by any stretch, power. Be sure to Loctite the muffler as it has a tendency to come loose easily.

I had problems starting it on and off for most of the flying season last year. I set the valves, replaced the plug, cleaned the carb, but still no joy. It finally quit altogether last fall and I sent it to Hobby Services. The ignition had failed completely. Hobby Services replaced it free even though the engine was out of warranty.

Since then it has been a pleasure to operate and starts flawlessly, although still not by hand. I have not experienced the rocker problems posted on Youtube. I run Redline and Sunoco purple race gas at 32:1.
Kiva Flyer is offline Find More Posts by Kiva Flyer
Reply With Quote Quick reply to this message
Old 01-09-2018, 06:50 AM
74Ranch is offline
Find More Posts by 74Ranch
Registered User
74Ranch's Avatar
United States, VA, Midlothian
Joined Sep 2013
433 Posts
I bought one used about a year or so ago, and I set it up on my test bench. I had a devil of time getting it to run. turns out it was mostly me. I finally figured out that the carb setup is not like a walbaro carb at all, that the butterfly plate travels way past "full" throttle point. once I figured that out and set up the servo/carb to work properly it ran assume. just don't have anything to put it in at this time.
74Ranch is offline Find More Posts by 74Ranch
Reply With Quote Quick reply to this message
Old 01-09-2018, 10:32 AM
AA5BY is offline
Find More Posts by AA5BY
Registered User
Joined May 2016
19 Posts
I was given one by someone who had reached his patience limits with it.

The original ignition had crapped out and he had borrowed and substituted an RCexl ignition and the engine ran but not well.

First
The stock ignition had an rpm sense where it would not fire unless turned over rapidly by a starter. OS intended the engine to be started with a starter.

Second
The engine given to me had two problems... it was missing the ball and spring to the PCV valve and it needed an ignition. My first test of the engine yielded only 8lbs of static thrust.

An RCexl ignition substitute would work, but the timing was wrong because of the differences in the way the OS ignition fired, it using a time delay scheme whereas the RCexl uses a release of dwell firing.

Just substituting an RCexl using the stock pickup yielded 15° btdc timing, way too early. The fix was to install an RCexl pickup and that required elongating the slots so as to use the two stock mounting screws. To obtain 28° timing requires positioning the RCexl sensor very close to one of the screws... so close that the screw head has to be ground off somewhat.

The missing ball and spring for the PCV left the crankcase open and thus reduced pulse pressure to the carbs fuel pump. When installing the valve.. static thrust increased to 11.5 lbs. After setting the timing to 28°, static thrust increased to 16.5 lbs where it is now and where it flies a 20 lb 90" bipe fairly well.

There is a reason it seems why OS didn't want the ignition to fire for hand propping. When mounted inverted, it can flood easily and when burning off the flood, when the plug does fire, the heavy fuel load can produce severe kickback.

I suffered a severe blood blister 1/4 wide and a 5/8 long across my middle finger to teach this truth. Though the prop didn't cut the skin, tissue damage was severe and took two months or so to heal and left the finger tip a bit numb from nerve trauma. I still hand start the engine, but now use a leather glove and even so, if detecting a flood, the plug is pulled and dried out.

Once the problems were sorted out and the character of the engine was understood... it has proved a good engine offering realistic early era sound with rpms and torque working well with a 20" prop for the slower flying large 20 lb - 90" bipe.
AA5BY is offline Find More Posts by AA5BY
Reply With Quote Quick reply to this message
Old 01-12-2018, 08:10 PM
Fletch88 is offline
Find More Posts by Fletch88
Registered User
United States, GA, Valdosta
Joined May 2017
34 Posts
Thanks for that heads up on the safety issue with flooding AA5BY. I have a high torque starter I think will turn it over. I haven't bench tested it yet but plan on it soon. I also have a welding glove I will use if I have to try to hard start it, but hopefully will not need to.

Thanks alfir all the other responses as well. Now to figure out what airframe to put it in. I think a TopRC Spitty is my first choice but I like the Bipe that the OS crew has on test flight flight video too. Any other advice on a good frame for it let me know please.

Thanks,
Walt
Fletch88 is offline Find More Posts by Fletch88
Reply With Quote Quick reply to this message
Old 01-12-2018, 11:46 PM
birdbrain is offline
Find More Posts by birdbrain
Registered User
Joined Oct 2009
355 Posts
I have this one set aside for mine
http://www.supercheaphobbies.com.au/...an-p-3072.html
birdbrain is offline Find More Posts by birdbrain
Reply With Quote Quick reply to this message
Old 01-13-2018, 09:39 AM
3DJP is offline
Find More Posts by 3DJP
Registered User
United States, NJ, Penns Grove
Joined Dec 2015
1,073 Posts
What does the book say for oil mixture.. 40:1 sounds lean for a 4 stroke.. every 4 stroke i have owned has been 15:1 or 20:1.. just check the last thing you wanna do is run lean!
3DJP is offline Find More Posts by 3DJP
Reply With Quote Quick reply to this message
Old 01-13-2018, 06:20 PM
74Ranch is offline
Find More Posts by 74Ranch
Registered User
74Ranch's Avatar
United States, VA, Midlothian
Joined Sep 2013
433 Posts
I run 20:1, because I use it in my 60r3, 3 cyl. Saito radial. I have only next run mine, and I'm not sure I'm going to keep it. I got way to many motors.
T
74Ranch is offline Find More Posts by 74Ranch
Reply With Quote Quick reply to this message
Old 01-13-2018, 10:23 PM
Fletch88 is offline
Find More Posts by Fletch88
Registered User
United States, GA, Valdosta
Joined May 2017
34 Posts
OS Oil Recomendation

Quote:
Originally Posted by 3DJP View Post
What does the book say for oil mixture.. 40:1 sounds lean for a 4 stroke.. every 4 stroke i have owned has been 15:1 or 20:1.. just check the last thing you wanna do is run lean!
I think Redline 40:1 or at most 32:1 would be fine. The manual says they approved Zenoah 2 stroke oil at 40:1 and Klotz at 50:1 ratio.
Fletch88 is offline Find More Posts by Fletch88
Reply With Quote Quick reply to this message
Old 01-15-2018, 01:58 PM
Fletch88 is offline
Find More Posts by Fletch88
Registered User
United States, GA, Valdosta
Joined May 2017
34 Posts
Quote:
Originally Posted by birdbrain View Post
Nice looking Ryan! I put it in my cart just to see what shipping would be. No way it can be $18 AUD to the USA? Is the build quality good on this frame?
Fletch88 is offline Find More Posts by Fletch88
Reply With Quote Quick reply to this message
Old 01-15-2018, 04:13 PM
birdbrain is offline
Find More Posts by birdbrain
Registered User
Joined Oct 2009
355 Posts
Yeh I doubt the shipping price . The larger (33cc ) one seems to be a bit scarcer than the 15cc one . I hope they still make it . You have get in contact with the owner before ordering as he doesn't have that much in stock he just orders it in . Check on the Phoenix website 1st to see if its still in production . The single seated has been one of those planes that I've liked since I was a kid and knew that when it came on the market I new I had to grab one cause they don't make em forever . cheers
birdbrain is offline Find More Posts by birdbrain
Reply With Quote Quick reply to this message
Old 01-15-2018, 07:08 PM
Stingerson is offline
Find More Posts by Stingerson
Registered User
Stingerson's Avatar
Joined Sep 2015
5 Posts
OS GF 40

I use an GF 40 in my Phoenix Top Model P-47.
2m span, 8.5kg weight.
(Needed 800gm in the front to balance)
18x10 apc.

Running standard 32:1. One minor tweak on the low end since the first start, haven’t touched the settings since.

I use a starter.
Stingerson is offline Find More Posts by Stingerson
Reply With Quote Quick reply to this message
Old 01-20-2018, 10:27 AM
swuest is offline
Find More Posts by swuest
Registered User
United States, AZ, Tucson
Joined Dec 2017
51 Posts
I have one lined up for some 30cc airframe, but it is still NIB.

In general, the 4-stroke gas/petrol engines don't put out much power.
I think that both Saito and OS gas 4-strokes are for people who like to hink with engines, and want only scale power.

I didn't like the OS 15cc gas engines, but their GT-22 seems to be running fine.
swuest is offline Find More Posts by swuest
Reply With Quote Quick reply to this message
Old 01-22-2018, 10:19 AM
Fletch88 is offline
Find More Posts by Fletch88
Registered User
United States, GA, Valdosta
Joined May 2017
34 Posts
Well I got it up on the bench this weekend and wow at the compression this engine has. I have a high torque starter but barely as able to get it cranked. I popped the prop nut several times when it backfired on me but finally got it running. Runs very well at idle and too end but does it ever have a severe vibration resonance it goes through when transitioning from idle to about 25% throttle. May be the wooden angle plate I built for running gas engines on but I think I love this engine. How about a Great Planes Giant SuperSportster for this engine? I could see that being a great combo.
Fletch88 is offline Find More Posts by Fletch88
Reply With Quote Quick reply to this message


Quick Reply
Message:


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion savox servo shipping issues cap23244 Radios 14 06-04-2013 09:10 PM