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Author Topic: OS 30 FS beginning stages of CL conversion  (Read 6450 times)

Offline Dane Martin

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OS 30 FS beginning stages of CL conversion
« on: September 17, 2015, 10:21:48 PM »
I've got the os30fs on the twister. Right now, just to fly we tried tying open the RC carb. First flight was inn suction and no muffler. It leaned out, so i decided to put the muffler back on and run muffler pressure. I couldn't get it running long enough to fly it. I found the intake was loose, and that must be the reason it leaned out. I tightened up all the screws and ran it on suction, no muffler. It sounded great and had a smooth, consistent 6min flight on 2oz.

I don't think i can leave it this way. When i pinch the fuel line to kill it, it stops almost instantly. Shouldn't it lean out and then die? Not an instant shut off? Its border line too rich in the air. I wouldn't really want to richen it up more, but the shut off is weird

Offline David Fountain

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Re: OS 30 FS beginning stages of CL conversion
« Reply #1 on: September 19, 2015, 09:48:31 PM »
Four strokes don't have the lean out/RPM increase like two strokes do, when you pinch off the fuel it will about instantly die that's something normal. The reason two strokes increase rpm when the fuel is shut off is because of fuel pooling in the crankcase and the larger volume and longer path the mix travels so it takes a second to clear out the case on shut off hence the RPM pickup. Hope this helps (David)
If it ain't broke, Don't Fix It!!

Offline Dane Martin

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Re: OS 30 FS beginning stages of CL conversion
« Reply #2 on: September 19, 2015, 10:29:27 PM »
Aha! That does help, because yesterday i flew it a couple times. Just fine tuning everything. The engine is running excellent at this point. Plenty of power. I flew through some of the pattern. Got through the vertical 8's and stopped because i haven't timed the tank yet.

I ordered some os nva assemblies from tower .Bob Z sent me a sweet manifold / venturi I'm going to try on this engine. I suspect I'm leaking air around the carb barrel right now.

Offline David Fountain

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Re: OS 30 FS beginning stages of CL conversion
« Reply #3 on: September 19, 2015, 11:20:11 PM »
Cool glad to be of help!  :)
Just make sure you don't over lean it. (David)
If it ain't broke, Don't Fix It!!

Offline Robert Zambelli

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Re: OS 30 FS beginning stages of CL conversion
« Reply #4 on: September 22, 2015, 08:19:01 AM »
Dane - the small OS 4S carb barrels are VERY LEAK PRONE.
They tend to leak at the lever. Here's what I do.

1) remove the throttle lever
2) clean up the barrel and lever with alcohol
3) run a bead of RTV at the barrel face
4) reassemble in the wide open position

I've never had a problem with this fix.

Bob Z.

Offline Dane Martin

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Re: OS 30 FS beginning stages of CL conversion
« Reply #5 on: September 22, 2015, 07:21:57 PM »
Thanks Bob Z!
I tried to call you the other day. I'll send a pm. I got some stock intakes to send you

Offline Dane Martin

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Re: OS 30 FS beginning stages of CL conversion
« Reply #6 on: October 05, 2015, 11:39:14 AM »
Here's Bob Z's intake. I used a normal os 40 fp springy nva i bought from tower. The only thing i had to do was make that little aluminum spacer in pic 2. I like this set up better on this plane than the modified carb i had on it. No muffler and running on suction.

Offline Dane Martin

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Re: OS 30 FS beginning stages of CL conversion
« Reply #7 on: February 04, 2017, 10:35:16 PM »
Long time, no update.
So, the Bob Z intake was real cool. Very nice and smooth consistent runs. Then the plane was crashed and repaired. I hadn't flown it in a long time. I finally flew it last weekend and it wasn't as consistent. I found the venturi was cracked at the cross drilled hole for the spray bar.
I made a new one out of nylon. Just drilled out a .257 ID nylon spacer I got at home Depot. I drilled it out to 3/8's and pressed it over the intake with a C clamp. Cross drilled it for the OS springy NVA again.
Will test tomorrow morning!

Offline Dane Martin

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Re: OS 30 FS beginning stages of CL conversion
« Reply #8 on: February 05, 2017, 06:05:22 PM »
Ok, so the .257 venturi might a little too much. I'm not 100% positive though. I'm using a 4oz tank but only loading 2oz of fuel. So I might be just iffy on the fuel delivery.
I'm going to change to a nice 2oz tank that I know works. I'm not saying my run is bad. Just not quite there yet.

The plane however, is rock solid. Makes it much easier to tune the engine knowing the plane is trimmed nice.

Offline Dan McEntee

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Re: OS 30 FS beginning stages of CL conversion
« Reply #9 on: February 05, 2017, 08:22:06 PM »
  Hi Dane;
     The .257 intake sounds huge for a .30.  On my Saito .56, I only have about a 6mm hole and the adjusting screw that Bob Reeves advocates. Four strokes are all about fuel draw. I would get the intake size down to less than 4mm. Keep fuel line runs short, and try muffler pressure. I run pressure and a regularly plumbed clunk tank, no unifow. I use the higher pitch prop/low RPM set up like Bob Reeves developed. I only have the Saito .56 powered Score right now, but have had good success since I tried the Reeves program. Through the year  or more of trying to tame the Saito, I have come to the conclusion that four strokes are just a different animal. You can't operate them like a two stroke, they make a different kind of power. I like it a lot, but not quite ready to sell all of my two strokes just yet!
   Type at you later,
    Dan McEntee
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Offline Dane Martin

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Re: OS 30 FS beginning stages of CL conversion
« Reply #10 on: February 05, 2017, 09:35:47 PM »
Excellent point sir. The next venturi I have to try is .195 or 4.95mm.
It ran better with a couple layers of panty hose over the venturi. So obviously it's too big. I'll have to see if I have a 4mm bushing. If not, I'll make one. Just nice to be lazy sometimes! Lol

Offline Dane Martin

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Re: OS 30 FS beginning stages of CL conversion
« Reply #11 on: February 05, 2017, 09:49:08 PM »
Edited for nonsensical rambling....

Offline Target

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Re: OS 30 FS beginning stages of CL conversion
« Reply #12 on: February 05, 2017, 11:00:22 PM »
Subscribing due to interest in 4S...
Regards,
Chris
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Offline Dane Martin

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Re: OS 30 FS beginning stages of CL conversion
« Reply #13 on: February 07, 2017, 07:35:44 AM »
Glad to hear from you again Chris! I've got several 4c planes going. In fact, I think all my "stunt" planes are 4c. Like Dan mentioned, I've actually done the Reeves method mods to one OS 40 FS. It works really nice on an OS engine.

Nothing new last night. Kids had a school skating day, then the LVCB club meeting. Long day, lol

Offline Dane Martin

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Re: OS 30 FS beginning stages of CL conversion
« Reply #14 on: February 12, 2017, 12:01:36 PM »
Ok so.... here's a Bob Reeves mod for an OS carb. I made this two years ago for a .40 FS and that engine is just sitting. It was in my banshee, which I generously loaned out as a trainer to everyone. Eventually it got gaped out beyond my desire to repair.

I'll borrow this off the .40 for now. When I get a lathe again, I'll make another.

The spigot is modified to be flush with the ID of the barrel. This allows the screw to go in pretty far and not disrupt fuel flow. The nylon screw is a number 10, matching the ID of the barrel. The barrel is actually the only part I made on the lathe.

Offline Dane Martin

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Re: OS 30 FS beginning stages of CL conversion
« Reply #15 on: February 12, 2017, 12:06:28 PM »
The nylon screw threaded into the new aluminium barrel.

Offline Target

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Re: OS 30 FS beginning stages of CL conversion
« Reply #16 on: February 12, 2017, 12:58:10 PM »
I'm kinda lost here. Does the nylon screw act as an adjustable venturi?
Regards,
Chris
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Offline Dane Martin

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Re: OS 30 FS beginning stages of CL conversion
« Reply #17 on: February 12, 2017, 01:06:05 PM »
I'm kinda lost here. Does the nylon screw act as an adjustable venturi?

Yes. It's basically a "throttle" valve. Bob has made many articles on this here on SH. It kinda just boils down to a more consistent and leak proof way to adjust the needle to whatever RPM range you are going for.

I'm not smart enough to explain it. I can just make the parts, follow directions and tune a plane to fly good. Lol

Offline Bob Reeves

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Re: OS 30 FS beginning stages of CL conversion
« Reply #18 on: February 15, 2017, 04:46:04 AM »
Probably a good time to re-post this link.
http://www.tulsacl.com/SaitoCarb.html

Lots of good info (at least what I discovered worked) at the bottom after the cab mod instructions.


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