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Author Topic: McCoy 35 will not draw fuel  (Read 1708 times)

Offline Ronald Eshleman

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McCoy 35 will not draw fuel
« on: April 12, 2010, 06:27:36 PM »
Hi,

      Today I was trying to start a McCoy 35 on the test stand with a standard vented wedge tank.  It would only stay running with my finger on the venturi.  It would run 4 cycle.  When I took my finger off, it would stop.  The needle valve (original) was set between 3 1/2 and 4 turns. The fuel was Powermaster 10:29.  Any ideas?

Ron Eshleman



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Offline Tim Wescott

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Re: McCoy 35 will not draw fuel
« Reply #1 on: April 12, 2010, 06:53:09 PM »
Just the usual:

1: Clogged needle valve -- how long has it been since the engine was run?  I got back into the hobby in a big way a few years ago after a 15 year hiatus, and all of my needle valves were full of dried castor.  It makes quite a plug.

2: Air leaks, either at the fuel tank/tube joint (you'd see bubbles in the line), at the tube/needle joint (you'd only see bubbles if you looked really close, then your vision would be blocked by the blood from your forehead), or in the needle housing.

3: (long shot) do you have good secondary compression?  If the crankcase is leaking air then you won't draw fuel, and a bazillion other things will be wrong.
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Offline Jim Thomerson

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Re: McCoy 35 will not draw fuel
« Reply #2 on: April 12, 2010, 07:37:00 PM »
Maybe a leak around the backplate.  The paper gasket is fairly fragile, and if the backplate has been opened up it could have been torn.  Check that all screws are tight.  The needle valve body should be tight with no leaks.  Your basic problem is that you have one or more leaks.
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Online Brett Buck

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Re: McCoy 35 will not draw fuel
« Reply #3 on: April 12, 2010, 08:05:15 PM »
Quote from: Ronald Eshleman on April 12, 2010, 06:27:36 PM
Today I was trying to start a McCoy 35 on the test stand with a standard vented wedge tank.  It would only stay running with my finger on the venturi.  It would run 4 cycle.  When I took my finger off, it would stop.  The needle valve (original) was set between 3 1/2 and 4 turns. The fuel was Powermaster 10:29.  Any ideas?

    I like Jim's idea. But another would be that the engine is missing a venturi insert. Most of the McCoy front-rotor engines I have seen are supposed to have a steel insert to reduce the choke area over just using the bore of the case. Without that it won't draw fuel very well at all.

     Brett
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Offline RandySmith

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Re: McCoy 35 will not draw fuel
« Reply #4 on: April 12, 2010, 10:05:03 PM »
Quote from: Ronald Eshleman on April 12, 2010, 06:27:36 PM
Hi,

      Today I was trying to start a McCoy 35 on the test stand with a standard vented wedge tank.  It would only stay running with my finger on the venturi.  It would run 4 cycle.  When I took my finger off, it would stop.  The needle valve (original) was set between 3 1/2 and 4 turns. The fuel was Powermaster 10:29.  Any ideas?

Ron Eshleman





as Stated make sure you have everything clean and open
It sounds like you may have a spraybar that is topped up, or the orifice hole
I would take out the NVA and tale it apart clean it with acetone then blow it out with WD-40 or the like
Reassemble and try it again

Randy
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Online Brett Buck

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Re: McCoy 35 will not draw fuel
« Reply #5 on: April 12, 2010, 10:32:23 PM »
Quote from: RandySmith on April 12, 2010, 10:05:03 PM
as Stated make sure you have everything clean and open
It sounds like you may have a spraybar that is topped up, or the orifice hole
I would take out the NVA and tale it apart clean it with acetone then blow it out with WD-40 or the like
Reassemble and try it again


Somewhat on topic, I have been looking for a source for these ever since my Sullivan cleaning kits all got given away. And, gee, if one of our "cottage industry" suppliers called them up and asked for just the two sizes we need in bulk, they would be pretty cheap.


   http://www.justmanbrush.com/catalog/plugins/lineitems/browse.asp, select "micro brushes"

   I think you only really need the smallest two.

   Brett
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Offline Kim Mortimore

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Re: McCoy 35 will not draw fuel
« Reply #6 on: April 13, 2010, 12:20:40 AM »
Quote from: Brett Buck on April 12, 2010, 10:32:23 PM

Somewhat on topic, I have been looking for a source for these ever since my Sullivan cleaning kits all got given away. And, gee, if one of our "cottage industry" suppliers called them up and asked for just the two sizes we need in bulk, they would be pretty cheap.


   http://www.justmanbrush.com/catalog/plugins/lineitems/browse.asp, select "micro brushes"

   I think you only really need the smallest two.

   Brett

Based on my experience, this definitely seems on topic--especially when you have a pesky hair or clothing fiber from the cheap nitro stuck in the needle body even after leaning your full weight on your syringe and propelling a power-wash stream of fuel 20 feet away, smack dab onto your buddy's freshly rubbed out super-stunter.   LL~ 

I was told last week that dental "flossing" type mini-brushes from the local drug store work.  I have not yet checked these out.  Has anyone checked them out already?
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Offline Jim Thomerson

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Re: McCoy 35 will not draw fuel
« Reply #7 on: April 13, 2010, 09:02:43 AM »
Another place a McCoy 35 can leak is the gasket between the crankcase and cylinder. HB~>
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Online Paul Smith

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Re: McCoy 35 will not draw fuel
« Reply #8 on: April 13, 2010, 02:03:51 PM »
Having gotten the engine to fire at all, you are in the upper 50% of McCoy 35 owners.
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Offline Ronald Eshleman

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Re: McCoy 35 will not draw fuel
« Reply #9 on: April 14, 2010, 08:26:08 PM »
 
Gentlemen,
Thanks for the advise.  I've had success!!  I removed the spraybar and cleaned it with WD-40 and high pressure.  Checked the needle valve for play and from my stash of old McCoy parts created a new needle assembly that seemed more snug.  I also replaced the spraybar with the center hole turned down in the plane of the the venturi angle.  Then I replaced one head screw that appeared to be a bit short.  Tightened all phillips screws, cleaned the fins around the head and applied several drops of engine after run oil.  The compression felt much better!  Today after school was the magic moment.  2 very successful runs of 4-5 minutes mostly at 4 cycle on the verge of 2.  The starting was easy.  The needle ajdustment was very consistent and the motor is now installed on a bi-plane I'm about to take on a maiden voyage. Thanks for the insights and I'll be back again I'm sure!  Happy flying to all!

Ron Eshleman
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Offline RandySmith

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Re: McCoy 35 will not draw fuel
« Reply #10 on: April 15, 2010, 02:54:26 PM »
Quote from: Brett Buck on April 12, 2010, 10:32:23 PM

Somewhat on topic, I have been looking for a source for these ever since my Sullivan cleaning kits all got given away. And, gee, if one of our "cottage industry" suppliers called them up and asked for just the two sizes we need in bulk, they would be pretty cheap.


   http://www.justmanbrush.com/catalog/plugins/lineitems/browse.asp, select "micro brushes"

   I think you only really need the smallest two.

   Brett


Hi Brett

You maybe right that they would be cheaper, but you can buy these now at the drug stores  , look in the toothpaste dept at flossers, they have several sizes and types of very small brushes like this
I buy them at Walgreens
Randy
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