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O.S. GF40 4st gas

Old 05-06-2017, 05:35 AM
  #201  
marksp
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Interwebs

I suggest search, search, search...

As for me, I hope it sounds at least as good as stock. I'm prolly a week or so away from running and I've never heard the GF w/Keleo combo!

Cheers
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Old 06-16-2017, 06:35 AM
  #202  
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Cool

Originally Posted by marksp View Post
Interwebs )

I suggest search, search, search...

As for me, I hope it sounds at least as good as stock. I'm prolly a week or so away from running and I've never heard the GF w/Keleo combo!

Cheers
This response does not sound like you're "sharing"
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Old 06-16-2017, 06:45 AM
  #203  
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Originally Posted by karolh View Post
This response does not sound like you're "sharing"
Putting it in nicer terms, he WOULD mind sharing and so maybe it's not a hobby for him.
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Old 06-16-2017, 02:17 PM
  #204  
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Originally Posted by PCT View Post
Putting it in nicer terms, he WOULD mind sharing and so maybe it's not a hobby for him.
Possibly.
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Old 06-16-2017, 09:30 PM
  #205  
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I put a saved search on eBay. I put a saved search on RCU marketplace. I created a Google alert. I searched RC Groups...i figured somebody had one from a crashed plane, or one that was never used, or an extra. Net - searched until I found one.
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Old 02-21-2019, 02:50 PM
  #206  
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Originally Posted by sandseeker View Post
Fitted and ran with the turboheader....not at all quiet! will sound nice in the air.

chris
Sandseeker,
This a great install. Your going to like the sound.
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Old 02-24-2019, 01:03 PM
  #207  
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Default Carb kit ?

anyone know the Walbro carb kit part # or the specific Walbro carb part #? Id like to freshen up the carb for next season :-)
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Old 05-10-2019, 09:18 AM
  #208  
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Default Carburettor Mods

Firstly - Mark the carb is a WT-1070. So a WT series refresh kit will do the job.

Anyway, back to the reason for posting. I've been wrestling on and off for about 12 months with a GF40. The conclusion I've come to about the carburation is:
  • If you set it up as OS intend, you will have a rock solid idle, fantastic pick-up and good high throttle performance. However, the midrange will be very poor, running very rich.
  • With careful adjustment, you can get lovely smooth running from about 2700rpm to W-O-T. However, you cannot get a stable low idle as the idle mixture is far too rich.
From reading around the forums, the first option is good enough for a lot of applications and folks. But for me, I have the engine in a scale civilian aircraft and it spends most of its life at 1/3 to 3/5 throttle with occasional trips to high power for a Lazy Eight or Chandelle. So it has to run well in the midrange.

In the second case, the tickover problem is caused by the need to close the butterfly more than usual to get the tickover down with the not-too-rich mixture. I believe this accentuates the effect of the little half-moon cut-out in the butterfly valve, ensuring that the majority of the air going into the engine is whistling straight over the third slow running fuel hole and giving a rich tickover. So I removed the butterfly, filled the half-moon with solder and dressed it back to a disk shape, theorising that this would mean the butterfly would need to be open a little at tickover and less of the air would be directly flowing past the fuel hole. Sure enough it was now a bit lean at tickover - I had to set the slow running needle about 1/4 turn richer to get a good idle, but this was enough to upset the midrange a bit. So I removed the butterfly - several times - each time using a needle file to enlarge the half-moon until the idle was about right with slow running needle where it needed to be for a good midrange. Bye eyeball, I reckon the half-moon I ended up with was about 20% of the area of the original - pretty damned small!

Time will tell whether this is a good long term solution, but the last couple of flights I had today were the first with this engine where I walked the model out with a solid 1800rpm tickover, taxied, took-off and flew the entire scale schedule with the engine purring at all throttle settings.

I'd be interested if anyone else has similar experience with this engine and any other solutions!
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Old 05-10-2019, 06:41 PM
  #209  
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I had a similar situation where it sounded like the mid-range was running too rich and stumbling, but idle & top end were fine. This was initially the condition of the engine. As it went through the break-in period, this problem completely went away as I burned more fuel through the engine. I don't see this as a permanent condition. Now I'm delighted with the engine & would buy another as soon as I save up the $$ for my 1/4 scale Pup.

Greg

Last edited by Eindecker_pilot; 05-10-2019 at 06:50 PM.
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Old 08-29-2019, 11:04 AM
  #210  
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Hey all,

I was given one of these engines by a fellow flyer, he did something really bad with it, and it means to get it running I need to spend around $250 on it to get it right again. One of the things that needs replacing is the con-rod. I have stripped the engine down and noticed there is a stop screw on the big end, and I need to get it off. According to parts photo's it is a threaded screw so should be able to undo with a screwdriver, but it is a very narrow slit for a crew driver, and it is also a long slit. Anyone got any tips on how to remove this.
I see some people have had PCV' valves missing, others with the ball/spring installed incorrectly. Which way is it supposed to go. Assuming it needs to draw air INTO the engine, then the spring would go in first, then the ball, and then the nipple, is this right?

Regards,
Andy
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Old 08-30-2019, 11:53 AM
  #211  
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As confirmed by "the pope", that stop screw is indeed, a left hand thread. I got it off without too much of a fight, but when replacing, should I put some loctite on it, or is that a waste of time?
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Old 10-17-2019, 09:59 AM
  #212  
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Just ordered one of these for my Hangar 9 Fokker D7 WW1 bipe.

The engine will be mounted with the cylinder up, as the crank on this plane is in the bottom of the aircraft.
Should I be worried about less lubrication to the rocker box ?
Anyone else run it with the cylinder upright ?


Aslo, seen the GF80 yet ? :-)
This seems to be a UAV engine, but still looks cool


And also a GF30II







Last edited by SJN; 10-17-2019 at 10:02 AM.
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Old 11-08-2019, 01:36 AM
  #213  
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Does anyone know what the thread is of the exhaust pipe fitting? I am looking to but a right angle and then find out whether any of the OS flex pipes will fit on it. But I need to find the thread sizes and cannot see any info on web or manuals? The same goes for the prop nuts...

Anyone help?

Thanks and regards
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Old 11-08-2019, 04:15 AM
  #214  
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Cathurga,

The exhaust port on the GF 40 has a 16x1mm thread. I don't believe you will find a 90 adapter that will work with the flex pipes.We have other options available on our website.
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Old 11-14-2019, 05:46 AM
  #215  
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Originally Posted by cathurga View Post
Hey all,

I was given one of these engines by a fellow flyer, he did something really bad with it, and it means to get it running I need to spend around $250 on it to get it right again. One of the things that needs replacing is the con-rod. I have stripped the engine down and noticed there is a stop screw on the big end, and I need to get it off. According to parts photo's it is a threaded screw so should be able to undo with a screwdriver, but it is a very narrow slit for a crew driver, and it is also a long slit. Anyone got any tips on how to remove this.
I see some people have had PCV' valves missing, others with the ball/spring installed incorrectly. Which way is it supposed to go. Assuming it needs to draw air INTO the engine, then the spring would go in first, then the ball, and then the nipple, is this right?

Regards,
Andy
I think the ball goes in first and then the spring.
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Old 12-08-2019, 12:14 AM
  #216  
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Well its been a while since posting here, and I have eventually managed to get the engine mounted on a test stand......but its not all plain sailing...

AA5BY, firstly to respond to your comment above, I believe that the spring goes in first, and the ball sits in the back of the nipple. Once installed, you can blow INTO the crankcase, but you cannot suck air out the nipple. This kinda makes sense, given that the forcing the PCV closed under pressure, will allow gases to pass into the cam area and up into the valve box. Its a smart system, I like it. But as mentioned by others, over-revving the engine is likely to interrupt that process, with detrimental effect.

So, mounted the engine and put some Stihl HP, mixed 30:1 with 95 pump gas, in the tank. The engine was given to me, and they did not give me the ignition unit, nor was I provided with the pickup sensor. I have installed a standard Rcxel sensor, supposedly for a DLE-61 engine, and the CDI is from an NGH 38.
Hand starting seemed out of the question, and considering there are a lot of 'variables' in the ignition department, I decided to use the Align starter that I have. Its quie a powerful unit, and swings my Saito FG60 without a problem, as well as a Saito FG40 and the NGH38...
I dont have a servo to operate the throttle on the test stand, so just installed the idle stop screw, and got it just off 'closed position'....between the ignition timing and the throttle position, it was a bit of a problem getting it to swing nicely. At one point it would go through one rotation, and then fire (BTDC obviously), and stop it dead! I retarded the timing as much as possible, and managed to get it swinging through multiple revolutions, and eventually it fired. I noticed that there is a LOT of compression on this thing, and if you open the throttle too much, it sucks in even MORE air and the compression goes UP!
It was running at a fast idle but as soon as you try and advance the throttle, it just dies. I opened both needles to 1.5 turns, and fired it up...much better...managed to set the high needle to give me just on 6500rpm on a cheapy 18x10 wide blade prop, which I though was pretty good. Tuned it back to 6350 so its not rich when it unloads. Its very good, but there seems to be something not quite right, the idle is a little erratic, but given that its got new piston, rings, con-rod and bearings, it might take some time to bed in. I also need to go and check the ignition timing again. I have heard the OS ignitions had a weird curve, or they had some trickery built in to the curve. The NGH ignition curve is also apparently a bit odd. So I will try a simple Rcxel unit and see if its any better. Most engines run well on a 28Deg BTDC curve, that is electronically retarded to 4-5 Deg BTDC at starting...this one should be no different.
The carb is also quite sensitive on the needles, and I did have a mid/low-range 'rough or flat spot' which is typical of Walbro carbs, hopefully sorting the timing will allow more accurate tuning to reduce the mid-range stumble.

My FG40, NGH38 are also engines that just DO NOT LIKE hand starting, and expect this one will be the same. Given that I paid nothing for it, forked out $200 to get new parts and have ignition units lying around, it could be a good find...I really dont like the huge muffler, and am reluctant to spend money on a Keleo or Turbo header. I have no flight restrictions and the ideal component would have been an 90Deg Elbow and some of the flex pipe that OS sells, seems like the 16mmx1mm thread might prove difficult to find such an animal...

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Old 12-08-2019, 05:40 AM
  #217  
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Carthurga,

I have a TurboHeader for this engine that is anodized black. It was a experiment and the anodizing didn't take very well at the weld. I can make you a super deal on it. You would need our RCS16x15S adapter to mount it.
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Old 12-08-2019, 11:28 AM
  #218  
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Appreciate the offer, and may take you up on it. I was thinking of putting your elbow, and then a flex pipe. I think OS do a 15x1mm flex pipe. Your elbow is 16x1mm male, and 15x1mm female side right?
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Old 12-08-2019, 11:57 AM
  #219  
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The RCS16x15S adapter has a 16x1mm male and 15x1mm female. Flex pipes without a jam nut to tighten will not work on our adapters.
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Old 12-08-2019, 10:08 PM
  #220  
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Does anyone know whether OS used Rcxel CDI tech when building the Ignition module? I am trying to figure out whether the curve is different to othe modules. I saw a thread once (not here, by the looks of a search, maybe on another forum) where people were saying that OS programed the CDI not to fire at low rpm, meaning that user would have to use a starter...and not hand start, but there are many people who seem to be able to flick start it easy...There was also talk that the timing is not set at 28Deg as there was some proprietary CDi programming
Any engine with a 'near-to-standard' curve, will work at 28Deg timing. I am hoping it is this simple, so I can use an olff the shelf ignition.
If anyone has info on this, I would be grateful to hear about it.

Regards
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Old 12-09-2019, 01:44 AM
  #221  
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One of the guys at my field hand starts his pretty easy on his cub . The same with his OS 33GT 2 stroke.


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