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Help changing cox medalion venturi

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Help changing cox medalion venturi

Old 03-08-2011, 06:58 AM
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sealdoggy
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Default Help changing cox medalion venturi

Hi Folks I'm a newbie here, my name is Steve Agrella, I live in California been building and flying control line models on and off for 40 years, I'm just getting back into because of my Grandsons.
My question is this, I purchased a Cox Medalion 049 on e bay, unfortuantely it has a cracked venturi across the bottom, I purchased a new venturi but not sure how to install it.
Can someone be kind oenough to give me some direction on how to replace it please.

Best Regards

Steve
Old 03-08-2011, 09:15 AM
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hllywdb
 
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Default RE: Help changing cox medalion venturi

Hi Steve,
It's fairly straight forward.
1. Remove the prop
2. Remove the collet in front of the venturi (It threads off, righty tighty, lefty loosey looking from the front)
3. Slide the venturi forward off the crankshaft. This may take some "pursuesion" if it has a lot of castor built up.
4. Slide the new one on.
5. Tighten the collet.
6. Remove the needle from the old one. Then push the spray bar out (It only slides one way)
7. Transfer the spray bar to the new housing. Screw in the new needle.
8. Attach prop, fill tank with fuel, attach glow igniter and flip prop while swearing loudly until engine starts.

Bill
Old 03-08-2011, 09:31 AM
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Jim Thomerson
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Default RE: Help changing cox medalion venturi

1a. Remove drive washer. Take the engine apart, backplate off, cylinder and piston off. Put a 5 x 40 screw in the crankshaft and drive it out of the case with light taps with a hammer.
2.

Be careful removing the spraybar as there is a tiny C-clip holding it in. Easy to lose.

When you are ready to start the engine, prime the exhaust with the piston up, Open the needle about three turns, choke it a couple of times, Attach glow driver, and hit the prop forward with your gloved finger. With a little practice, this will work every time. Flipping the prop on that engine is an exercise in futility.
Old 03-08-2011, 10:11 AM
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sealdoggy
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Default RE: Help changing cox medalion venturi

Thanks Gentlemen, couple of schools of thought here , I get the idea which one to follow though ???
Old 03-08-2011, 10:42 AM
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Default RE: Help changing cox medalion venturi

Hi Steve,
Same school of thought generaly. I have done it both ways on the 049's and 09's and it will depend on your engine's condition. Most times I find the thrust washer will pull off by hand.

A lot of times the reason the venturi cracked is because of grunge build up between the crank and the plastic. In which case it is prudent to follow Jim's advise and disassemble the motor and clean it (not bad advise when buying a used motor anyway). If it just cracked because of age or a less than perfect landing, you can pull it off from the front and replace it. If it slides off fine, proceed, if it is stuck, best to disassemble and tap it out as Jim suggested.
Old 03-08-2011, 10:47 AM
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skaliwag
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Default RE: Help changing cox medalion venturi

A little pre-soaking in hot, not boiling water or a few minutes under the hair dryer might help
Old 03-08-2011, 10:50 AM
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sealdoggy
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Default RE: Help changing cox medalion venturi

Thanks so much for taking the time to answer my question.

Regards

Steve
Old 03-08-2011, 11:44 AM
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Remby
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Default RE: Help changing cox medalion venturi

Hello Steve;

I would suggest finding a Cox instruction sheet for your Medallion, the instructions give good details on working on the engine. Any Year would work for your needs.

Also, when you replace the venturi, do not over-tighten the retainer for the Venturi, just snug it lightly. otherwise, damage, or binding of the crankshaft/crankcase can happen.

As you are returning to the fray, the fuel avalable is not as it used to be, many here use the 25% Sig Champion with a extra ounce of pure castor per quart.

Keep us posted!
Old 03-08-2011, 11:59 AM
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Default RE: Help changing cox medalion venturi

Hi Steve,
Might not hurt to mention that Bernie is a great source of parts now. They have done a lot to keep the Cox engines alive. http://coxengines.ca
Old 03-08-2011, 12:58 PM
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sealdoggy
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Default RE: Help changing cox medalion venturi

Wow, you guys are wealth of information, I'm excited to get the boys up in the air.

I have so many fond memories of all those younger days, started off with the Cox PT19, then I built the infamous Flight streak, I had a couple of VooDoo's, graduated to a Ringmaster witha Mccoy Red head .35, then a Nobler etc.

I'll probably get dizzy and fall down now, especially flying this 1/2 A on 35ft lines, I'll just put a 1/2 tank in and pray like heck.....lol

Steve
Old 03-09-2011, 07:34 AM
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Default RE: Help changing cox medalion venturi

One more thing.. If I remember right, when you're on step 5 don't thighten too hard as an over-tightened collet can also cause the plastic carb body to crack / break.


You can turn that engine into a screamer with a Dual Boost SPI Cylinder / light piston setup and high compression head. Good luck with it. My son an I fly a small combat wing powered by my "screamer" Medallion around 25ft lines. Dizzying indeed

Good luck with it.
Old 03-09-2011, 07:49 AM
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Cox International
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Default RE: Help changing cox medalion venturi


Replacement instructions for carb bodies is a common question we receive and below is a copy and paste of our standard reply. Although geared towards the TD series, it nontheless aplies to the Medallion series as well.

Cheers
Bernie
www.coxinternational.ca


Carburetor body installation
· Unscrew needle valve
· Unscrew venturi
· Remove needle valve body & spring
· Remove cylinder
· Remove backplate
· Remove piston
· Stand crankcase upright, drive-plate facing upwards
· Insert prop screw as deep as possible
· Tap with hammer until drive-plate separates from crank
· Unscrew collet
· Wedge flat tool between carb body and crankcase and twist
· (carb body is pressed on, not screwed)
· Press in new carb body
· Re-assemble engine
For ease of dis-assembly / assembly we sell the following tools:
· Wrench
· Dis-assembly tool
· Assembly tool
Old 03-09-2011, 05:00 PM
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Silvaire
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Default RE: Help changing cox medalion venturi


ORIGINAL: xenalook


Replacement instructions for carb bodies is a common question we receive and below is a copy and paste of our standard reply. Although geared towards the TD series, it nontheless aplies to the Medallion series as well.

Cheers
Bernie
www.coxinternational.ca


Carburetor body installation
ยท Unscrew needle valve
ยท Unscrew venturi
ยท Remove needle valve body & spring
ยท Remove cylinder
ยท Remove backplate
ยท Remove piston
ยท Stand crankcase upright, drive-plate facing upwards
ยท Insert prop screw as deep as possible
ยท Tap with hammer until drive-plate separates from crank
ยท Unscrew collet
ยท Wedge flat tool between carb body and crankcase and twist
ยท (carb body is pressed on, not screwed)
ยท Press in new carb body
ยท Re-assemble engine
For ease of dis-assembly / assembly we sell the following tools:
ยท Wrench
ยท Dis-assembly tool
ยท Assembly tool
Those are pretty good instructions to include with a new venturi, but I would suggest a slight change:

Put "Remove backplate" before "Remove cylinder" in the disassembly sequence.

It is much easier to hold onto the engine when removing the backplate if the cylinder is still in place.
Old 03-09-2011, 05:38 PM
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Cox International
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Default RE: Help changing cox medalion venturi

Great suggestion, Silvaire, and wewill amend the instructions accordindly.

Bernie
Old 03-10-2011, 07:21 AM
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sealdoggy
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Default RE: Help changing cox medalion venturi

Thanks everyone for your input, very much appreciated

Steve

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