The troublesome Corsair engine, the gruesome twosome, another Hero Testors McCoy .049 and the yellow prop returns.

rsv1cox Sat Jul 20, 2019 3:40 pm

The troublesome Corsair engine, I have another name for it but this is a family show.

Thought maybe the toothed venturi inlet had embedded into the soft pine, so I put it on stand-offs. Still no joy.

The troublesome Corsair engine, the gruesome twosome, another Hero Testors McCoy .049 and the yellow prop returns. P7140010

The troublesome Corsair engine, the gruesome twosome, another Hero Testors McCoy .049 and the yellow prop returns. P7140011

Then tried a whole new back-end postage stamp, same thing.

The troublesome Corsair engine, the gruesome twosome, another Hero Testors McCoy .049 and the yellow prop returns. P7160010

Basic problem is runs off the prime and quits. No fuel draw as observed through the tubing.

Thought maybe the fuel supply arraignment was at fault, or bad fuel.

Tried another Testors McCoy just received with the gruesome twosome and...……

The troublesome Corsair engine, the gruesome twosome, another Hero Testors McCoy .049 and the yellow prop returns. P7170010

Left hand yellow prop is drilled for the larger McCoy crank shaft so it gets a lot of use for those engines.

The gruesome twosome posted about here previously and friend.

The troublesome Corsair engine, the gruesome twosome, another Hero Testors McCoy .049 and the yellow prop returns. P7170011

They were not as bad as the seller had pictured, but both locked up so they got an A/F boil. Still locked up. First time I have seen this. Neither would move the piston. Heroic measures, profanity and burned hands finally got both to rock....slightly. More dipping into boiling A/F freed both but with considerable effort. Wow, new to me.

Rusty external cylinders got cleaned with the wire wheel and reblued which also coats the bore. A little Remoil and turning of the crank reveled out of round cylinders as evidenced by the bluing being scrubbed off and deposited on the top of the pistons.

Got out some JB bore paste and coated the cylinders and flipped the prop for ten minutes or so with little progress, still very stiff movement. Got out the drill and recoated the bores. Ran it for about 30 seconds which resulted in a nice smooth operation. Cleaned everything up and reassembled with new gaskets. Got a compression pop that any Cox engine guy would appreciate.

The troublesome Corsair engine, the gruesome twosome, another Hero Testors McCoy .049 and the yellow prop returns. P1010097

The troublesome Corsair engine, the gruesome twosome, another Hero Testors McCoy .049 and the yellow prop returns. P1010093

The troublesome Corsair engine, the gruesome twosome, another Hero Testors McCoy .049 and the yellow prop returns. P1010092

The troublesome Corsair engine, the gruesome twosome, another Hero Testors McCoy .049 and the yellow prop returns. P1010094

The troublesome Corsair engine, the gruesome twosome, another Hero Testors McCoy .049 and the yellow prop returns. P1010095

The troublesome Corsair engine, the gruesome twosome, another Hero Testors McCoy .049 and the yellow prop returns. P1010096

As for the Corsair engine, last chance.

I have fooled with this engine for years. The only thing I have never done to it is A/F boil it, unnecessary as it has excellent compression and yes, I know....if it has fuel, fire and compression it's going to run and it does, off the prime. It's problem is....no fuel draw as I said above. Yet, with the same fuel and setup the Testors engine ran fine drawing fuel even with out fingering off the venturi.

It's 103 degrees out in the garage right now. When I cools off I will give it one final try. If it doesn't run...probably. The first volunteer here - state-side gets it under these conditions. First - run it as received no alterations. Photo or video documentation. Then work you magic. If it doesn't run, hurl it. If it runs keep it with my congratulations. I would be happy to be rid of the thing...………………...But

Wait to see if I can get it to run first. I will post results here, then the first responder (victim)gets it.

Levent Suberk Sat Jul 20, 2019 4:25 pm

Perhaps reed don't move?

Mike1484 Sat Jul 20, 2019 4:38 pm

Possible case leak ? It has to hold vacuum and pressure to function and draw fuel . Does the cylinder have ports or is there blockage in them or to them ? If the intake is blocked on the screen end it should draw fuel . You will find the problem , don't give up .

Mike1484

rsv1cox Sat Jul 20, 2019 5:18 pm

Two different back ends. Different reeds tried.

The case gasket is in question. I have tried it with and without that gasket, but I believe it is for the cast case. Will replace it with a standard Cox gasket and see what happens.

**Cribbs74** Sat Jul 20, 2019 5:22 pm

You win the longest title for a thread award!

I am with Mike, sounds like you have a crankcase leak. Put that backplate under a magnifying glass.

If the backplate is sound then pull that spraybar and blow it out. That tiny outlet hole can easily clog.

Ron

rsv1cox Sat Jul 20, 2019 5:26 pm

Cribbs74 wrote:You win the longest title for a thread award!

I am with Mike, sounds like you have a crankcase leak. Put that backplate under a magnifying glass.

If the backplate is sound then pull that spraybar and blow it out. That tiny outlet hole can easily clog.

Ron

Same thing Ron, two different backplates same result. No fuel draw.

Could have divided this into three threads. My attempt to consolidate. Smile

Levent Suberk Sat Jul 20, 2019 6:10 pm

Yes, gasket is for cast case and leaks.

The troublesome Corsair engine, the gruesome twosome, another Hero Testors McCoy .049 and the yellow prop returns. Img_2012

**Cribbs74** Sat Jul 20, 2019 6:14 pm

You must have a case leak somewhere, assuming the spray bar is clear and the reed seals then you should be developing vacuum. Ain’t much to these things. Does it draw fuel when you place your finger over the venturi?

rsv1cox Sat Jul 20, 2019 7:08 pm

I guess some time ago after years of frustration with this engine I tried that gasket maybe just to see what would happen. Made no difference and must have just left it.

But this engines troubles go well before that as it never ran anyway even when on the airplane.

I replaced that gasket and headed for the garage. A comfortable 93 degrees now, turned into a sweat ball in about five minutes.

To check out the fuel supply I mounted the engine on the other side from the one I had used previously.

Same thing. No fuel draw, runs poorly off the prime. Engine has been cleaned many times my standard way and the NVA blown out with compressed air. Needle is fine. Can't finger the venturi when mounted.

Bummed....again, I mounted one of the just cleaned gruesome's. The one with the #6 cylinder, filled the tank primed and flipped. Started backwards. Ran in the house to get the camera..."without pictures it didn't happen!"

As bought:

The troublesome Corsair engine, the gruesome twosome, another Hero Testors McCoy .049 and the yellow prop returns. Grusom10

The troublesome Corsair engine, the gruesome twosome, another Hero Testors McCoy .049 and the yellow prop returns. Grusom11

The other cylinder is marked PL.

Flipped again, started running in the correct direction. Adjusted the NV...a screamer. Ran out the tank.

The troublesome Corsair engine, the gruesome twosome, another Hero Testors McCoy .049 and the yellow prop returns. P7200010

The troublesome Corsair engine, the gruesome twosome, another Hero Testors McCoy .049 and the yellow prop returns. P7200012

The troublesome Corsair engine, the gruesome twosome, another Hero Testors McCoy .049 and the yellow prop returns. P7200011

Tomorrow I will replace the horse shoe with the gruesome's tank and see what happens. Other option is to replace the horse shoe with one from a known good runner. If neither works, it get's hammered or off to the mailbox.

**Cribbs74** Sat Jul 20, 2019 8:22 pm

You are correct, you can’t get a finger on the venturi when mounted. Something to check before you bolt the tank on.

If you bolt a tank up and it works then you will know where the fault lies. Hope you get it.

Ron

Oldenginerod Sat Jul 20, 2019 10:19 pm

rsv1cox wrote:
The other cylinder is marked PL.

Bob. I'd suggest that cylinder should actually say P40. Simply an early Babe Bee with a specially ported cylinder for the P40 to give it a little more oomph to overcome a heavy poor flying model.

As for your Corsair engine, all I can come up with, if the back-end doesn't seem to be the issue, have you 1) checked if the crankshaft is a good fit in the case and not leaking there?
2) checked that the cylinder is screwed in straight, tight and sealing in the crankcase?
3) Now this theory is a doozie. Shocked

Have you checked that the cylinder didn't miss a manufacturing step and miss out on having the by-pass port(s) machined?. I've seen stuff like that in OK Cubs but never a Cox.

Two OK Cub examples- .06 reed engine which had no fuel hole drilled in the brass Venturi insert.
Second one was a brand new looking .049B car engine. Only ever just fired off the prime. Dismantled it and found that the crankshaft had no intake porting. I'm assuming that it mistakenly had a reed valve engine crankshaft installed.

Anyway, funny things happen, so check your bypass ports.

Rod.

rex f. Sun Jul 21, 2019 3:05 am

Check to see the reed is not being held closed by the retainer does happen

rex f. Sun Jul 21, 2019 3:16 am

Check if the bypasse have been machined so they connect eirh the exhausr
A big probability or is there alarge amount of piston clearance below the evhaust ports

rsv1cox Sun Jul 21, 2019 8:05 am

Well, the problem is in the back end.

Swapped the back end with the tanked engine and ran it twice. It started and ran fine although both times it started backwards. I thought the cammed spring starter prevented that!!!

If I thought the standard spring starter was bad, the one with the cam is a nightmare. I'm used to finger flipping and that springed starter caught me once so I started using a chicken stick. Once bitten...…..

So, I removed the BB's tank and swapped the gasket around on the Corsairs engine so it was next to the horse-shoe and tried it again. Same result, no fuel draw and runs off prime.

I have tried mylar, steel, and clear reeds but some how feel the problem is in that area. As I mentioned, this engine has been a problem since I got it many years ago. Maybe the plastic surrounding the reed is malformed.

This engine came out of the Corsair with the white propeller. Runs fine now along with the other Corsair, to bad they fly so poorly.

The troublesome Corsair engine, the gruesome twosome, another Hero Testors McCoy .049 and the yellow prop returns. P1010101

The troublesome Corsair engine, the gruesome twosome, another Hero Testors McCoy .049 and the yellow prop returns. P1010098

Runs great with the back end from the other engine.

The troublesome Corsair engine, the gruesome twosome, another Hero Testors McCoy .049 and the yellow prop returns. P1010100

Everything back to original. Only this is not the QZ engine with the #6 cylinder, it's the one marked P-something. Maybe P40 as rod said. My eyes are not what they used to be.

I always flush-out, blow out my engines after use. keeps them from locking up.

The troublesome Corsair engine, the gruesome twosome, another Hero Testors McCoy .049 and the yellow prop returns. P1010099

**944_Jim** Sun Jul 21, 2019 9:04 am

Hi Bob,

I may have missed this: Have you confirmed fuel is getting through the NVA? Maybe it is plugged.

Did you notice a difference in feel and compression bumps when turned with no fuel? Not necessarily dry, but with just a shot of prime?

If the Reed is failing in the original backplate, you'll feel the difference in the downward, crankcase compressing stroke. If you had a chunk of larger fuel line, you can test the reed by blowing air though it, and trying to suck air the other way. ISTR 5 mm fuel line will fit the backside of the venturi tube.

Are you good with backplates? Or do you need one?

rsv1cox Sun Jul 21, 2019 10:14 am

Thanks Jim, I haven't done the push/pull test.

Curious that it did not run with a known good postage stamp. I think it's a combination of things.

I haven't given up. Isolated to the backplate, now to investigate that. But it could be the fuel supply setup. Testors engines run fine on it though and I rotated the postage stamps backplate 90 degrees to get the supply even with the intake and fuel tank to no joy.

Thanks for the offer, but I'm pretty well set on backplates.

Bob

roddie Sun Jul 21, 2019 12:20 pm

Hi Robert, The two plastic backplates that wouldn't run; (orig. and postie)... try running those on a "known-runner" case and top-end. Be sure to open their needles an ample amount of turns from closed. I've found that I need to open certain needles more than others.. to get an engine to run after the initial prime. Also; the "postie" likely has a fine-thread NV and might require more turns "open" of its needle to start/run.

One more thing that wasn't mentioned; it's always a good idea to subject "new to you" and un-run Cox reed-valve engines to a decking of the rear (gasket surface) of the case. There are often uneven areas there, that a new gasket is expected to make up for.. and provide the proper sealing of the crankcase, which is crucial for proper reed-function.

A lite of glass from a small picture-frame placed atop another reasonably flat surface makes a good foundation for the decking-process. Obtain some ultra-fine (400+ grit) abrasive paper for atop the glass. Apply light but firm downward-pressure.. a few strokes at a time while moving the case in a circular motion over the paper. Observe the gasket-surface beforehand and after the first few strokes. You should see a smoother surface and also the transfer of aluminum to the paper. Don't be too heavy-handed.

Good luck! Thumbs Up

rsv1cox Sun Jul 21, 2019 2:19 pm

Now that's something I have never thought about Roddie, decking the case. Familiar to an old engine guy. I usually have 220 - 1000 grit wet/dry paper on-hand all the time. Flat glass too, great for mixing Bondo on. Bondo, my MG's middle name.

Bob

**Cribbs74** Sun Jul 21, 2019 2:51 pm

Sorry Bob, I probably should have mentioned the case needing sanding even when new, it’s a pretty common practice so I had assumed you had done that already.

I know you are tired about discussing the NVA but there are three holes, the one I am most concerned about is the one that resides in the venturi. If you blew it out from top to bottom that third hole in the middle could still be clogged.

An easy way to check is to attach a piece of fuel hose to the fuel inlet and blow into the fuel hose while slowly opening the NV. You should be hearing a hiss if that hole is clear.

Roddie brought up a good point, the needles like to be opened up to draw fuel well, did you ever cover the venturi and see if it pulls fuel?

rsv1cox Sun Jul 21, 2019 3:26 pm

Cribbs74 wrote:Sorry Bob, I probably should have mentioned the case needing sanding even when new, it’s a pretty common practice so I had assumed you had done that already.

I know you are tired about discussing the NVA but there are three holes, the one I am most concerned about is the one that resides in the venturi. If you blew it out from top to bottom that third hole in the middle could still be clogged.

An easy way to check is to attach a piece of fuel hose to the fuel inlet and blow into the fuel hose while slowly opening the NV. You should be hearing a hiss if that hole is clear.

Roddie brought up a good point, the needles like to be opened up to draw fuel well, did you ever cover the venturi and see if it pulls fuel?

Ron, I'm sending you that engine, it was always you or Kim. Sorry for you, too bad I like you both. If you can't get it running, send it to the Kimster, he can get anything to run. I owe you something anyway. I think I have your address, but PM it to me just in case.

I'm just sick of this engine. It's to you or the hammer. I have been really restrained in my contempt for this engine. Time and test fuel consumed over years has me up a rope. I have a couple of Enya's that have proved difficult but nothing like this and I always got them to run eventually.

Hopefully a few hours with it won't make you resemble your avatar picture...…. Smile

I DO NOT want it back!

Bob

**Cribbs74** Mon Jul 22, 2019 3:41 pm

sent you a PM last night.

rsv1cox Mon Jul 22, 2019 6:28 pm

Cribbs74 wrote: sent you a PM last night.

Thanks Ron, Got it, will mail it tomorrow.

BTW, I don't mind a little public humiliation should you get it to run as received. Hopefully it won't drive you to distraction as it did me.

Possibly you will find a cure and post it here.

Bob

**Cribbs74** Mon Jul 22, 2019 6:40 pm

Don’t worry Bob, if it doesn’t work for me it gets tossed in the parts bin. If I do get it to run I will post the fix. I imagine it’s not something readily apparent.

Edit: I forgot, if I can’t get it to run I am sending it to Kim and he can toss it in his parts bin lol!

NEW222 Mon Jul 22, 2019 9:30 pm

Coule there be any possibility of a small hairline crack in the horseshoe backplates? I remember reading about hairline cracks in horseshoe backplates somewhere before. And with a black backplate would make it even harder to detect.

balogh Tue Jul 23, 2019 1:05 am

That hairline crack was discussed somewhere here to be typical on the air intake of the grey backpkate of surestarts, near the screen but I do not think that causes starting problems.

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The troublesome Corsair engine, the gruesome twosome, another Hero Testors McCoy .049 and the yellow prop returns.

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