I recently acquired a red head McCoy 35 from a gentleman's collection.  It is on a Ringmaster probably from the late 5o's or 60's.  I cleaned up the spray bar and it runs well on the engine stand.  However back on the plane it runs 30-45 sec. with bubbles in the fuel line before shutting down.  I've not gotten in the air because of the stopping.  I cleaned the spray bar.  Reinstalled with the hole pointing down at the angle of the venturi.  Is that right?  I'm using 29% powermaster fuel and as stated it runs fine sitting vertical on the enging stand.  On the plane it sits outboard with exhast port aimed down.  I have the spray bar installed with the needle valve exiting up.  The fuel line comes out of the wedge tank at near entrance angle with port.  It goes down around the back of the motor and enters at the bottom on the venturi.  Compression seems good.  all screws are tight.  I've changed the glow plug several times...It sometimes stops after removing the battery.  The glow plug is a Fox plug. Hoping to get this ship in the air real soon!!

Randy posted while I was typing.  I see your problem a bit differently than he does.  While bubbles in the line is almost always the case at the END of th erun when the tank is about empty, your problem is when the tank is full!

Mind you, I will never purport to know half of what Randy does about engines.

QUOTE:
However back on the plane it runs 30-45 sec. with bubbles in the fuel line before shutting down.

It is because the engine is quitting right after you start it, with bubbles in the fuel line, that I wrote this:

The fuel is foaming due to vibration is the first obvious problem.  That has to be cured or it will never run right.  Make sure the prop is balanced first.   Could well be the nose is just weak from the years.  If it (the plane) is as old as you think, I am positive no epoxy was used in the nose construction.  Couple that with very short maple motor mounts, and that can easily cause vibration.

Possibly a small air leak in the tank, also.  Take th etank off, empty it and submerge it in water.  Block off the vents tight, and blow through fuel line connected to the feed line.  Air bubbles naturally mean a leak.

What *brand/heat range* glow plug?  A hot plug is probably necessary.  How are you setting the engine to run?  Are you running it n a 4-2 style? (that's how the old McCoys are meant to run).

Lots of reasons for it not running on the plane, but if it runs on the stand all right , then 99,999 times out of 100,000  it is a problem in the airframe.

Big Bear

1.  Check the venturi opening.  Maybe one of the past owners removed the insert or drilled it out.  A temporary fix, you can partially block half the opening with a wood plug.

2. Back in 1959, my father attempted to buy me a McCoy 35 for my birthday.  Mr. John Kilsdonk, the control line expert at the Royal Craft Bike & Hobby Shop advised my father that the McCoy would only lead to frustration followed by abandonment of modeling.  He was able to persuade my father into spending an additional $1.50 to upgrade to a Fox Rocket 35, which served me well.  I've always wondered if John tried to hit up my dad for $7.00 to step up to an OS Max III 35.

3.  There are a few satisfied McCoy 35 owners.  But there are many times more guys who quit because of them.  They are sort of the next step in running the gauntlet, for those who survive the Cox PT-19.

(ship)3.  There are a few satisfied McCoy 35 owners.  But there are many times more guys who quit because of them.  They are sort of the next step in running the gauntlet, for those who survive the Cox PT-19.

Hi Paul,

While there is a lot of truth in what you are saying, there are also a whole lot of people who stuck with it and had a McCoy .35 to start out with.

McCoys were often mistreated by unknowing individuals who used the wrong fuel and ran them too hard.  I've been lucky.  I've had the same McCoy Red Head since 1963 and it still runs great with MANY hours on it.  And who's to argue with George Aldrich?  He said the McCoys were the best times Stunt Engines that were mass produced.  No they are not the best engines ever produced when it comes to materials used by Testors.  The Lighting Bolt cases actually did do something to help the issues, but the pistons were still too soft for lasting a life time.

Yes there were, unfortunately, LOTS of QC issues with them as time went by, especially.  But, that has also happened to a lesser degree with about EVERY mass produced model engine.

Big Bear

   And because they were only $4!  The old "run it till it blows, then buy another one" effect.

     Brett

LOL!!!!!!!! so true! LOL!!!!!!

Bill

I'd also replace that 50 year old wedge tank with something a bit newer. Available and not too expensive from both Brodak and RSM. 

Just an update.  Today I ran a 3rd Fox .35 with Brodak 29% fuel.  It ran quite well.  Then to those 3 McCoy .35's.  The first engine was not tight on the fuse!  It looked like it was but....opps...about 4 turns to every bolt.  Then a restart...this time I could set the 4-2 and it ran the entire tank.  I then ran 2 other McCoy .35's setting each needle for 4-2. 

RIGHT TANK, RIGHT FUEL, SPRAY BAR CLEAN and POSITIONED correctly, MINIMAL VIBRATION, BALANCED PROP, STRONG BATTERY and NEW FOX GLOW PLUG.  Now I'm ready to FLY!!  That should be in the next day or 2 if the weather co-operates.  THANK YOU for all ADVICE.  GENTLEMEN, you make me smile!!!

Another great night running one of those McCoy 35's I've been working with.  Did a maiden voyage on a bi-plane I inherited from the 60's.  My friend Bob was there to see it fly.  He started the construction 50 years ago!  I covered it with tower coat in red black and white.  It is very sharp. He must have a 6 oz. tank in it?  It ran for 6 plus minutes.  Very nice run with 29% Caster/ 10% Nitro Brodak fuel and a Fox RC Long glow plug on 52' lines.  It was a memory making moment.  I've taken the many posts here to heart and success is becoming a reality.  Once again, thanks for the suggestions.  The Ringmaster is now flying well too.  Just need to tweek the needle valve a bit.  Right fuel, right spray bar setting, right glow plug and joy is at hand!