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McCoy BabyMac Question

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McCoy BabyMac Question

Post  NEW222 on Thu Mar 08, 2018 10:01 pm

So, I wanted a project engine and aquired a couple. First, and complete, is a Spitzy .045 engine. Turns over, but will clean it up before firing it up, or possibly let it go. Second, the reason I am here, is a McCoy .049 BabyMac. It is in rougher shape. The needle was missing, and teh back of the tank on teh rear of the engine is missing the backplate. So, I will just cut the tank as close as I can and use it that way. And as for the needle????? What to do. I do know that the OK Cub needles were nothing special, and have heard that back in the day, people making a needle out of a screw, and this is what I was thinking. Unless someone here may be able to help me figure out a way to remove the spraybar assembly and replace it. The threads are not on the outside, and whatever is inside looks very shallow, and almost non-existant? Anyways, I appreciate to hear any feedback from the members here to my plight. Would it be alright to use a homemade needle from a screw, as this would be th easiest? Thank you.

P.S. These both came with original documentation and tools.

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Re: McCoy BabyMac Question

Post  Mark Boesen on Thu Mar 08, 2018 10:32 pm

Use a couple dremel cutting discs (as you'll probably break one) to cut the tank. This is what Duke Fox did to the Fox .07's (tanks) he repo'd from Comet back in the day. I think a Wen-Mac needle will work on the McCoy. You might just make an aluminum backplate for the tank, wouldn't take that much more time to do. Cool little projects!




Last edited by Mark Boesen on Thu Mar 08, 2018 11:49 pm; edited 1 time in total
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Re: McCoy BabyMac Question

Post  NEW222 on Thu Mar 08, 2018 10:59 pm

Well, what the heck happened here? I typed out a little reply a few minutes before you posted saying I was probably going to make a backplate for this? So, now with your suggestion confirming my thoughts, I am now going to make a backarate for the tank. Thank you for your help. I wI'll keep an eye out for a WenMac needle to see if it fits.
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Re: McCoy BabyMac Question

Post  Mark Boesen on Thu Mar 08, 2018 11:48 pm

It does, but not sure if taper sets properly (they do look pretty close) threads are the same. It looks like the backplate of tank is just a disc pressed in, a guy could even cut one out of plastic...
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Re: McCoy BabyMac Question

Post  NEW222 on Sat Mar 10, 2018 3:05 pm

Ok. Similar to the other thread, the engine has been cleaned, repaired, and assembled. Now the last piece of the puzzle is to get or make a needle. Would anybody happen to know the thread pitch of a Wen-Mac or McCoy needle, so I may source out a screw in the meantime while I am searching one out? I do know for a fact that it is not 2-56, as I had already tried that. Anyways, thanks for looking and here it is. It is actually a nice looking little engine, as well, it is my first engine with a colored head! The gentleman I bought it from had 2 gaskets under the glow plug, one copper, and one steel(?). Is this a common thing, or should I remove one of them? I am also assuming a regular short plug can be used if I need one, fingers crossed I wont.

Now also, as I look at it, I would now kind of like to put it on a plane, but mounting it has me a bit confused. This is as the tank is held onto the crankcase by two bolts, and from what I read, these are to go through the firewall and mount from the backside. So, I am also assuming here that I pretty much need a profile plane with a plywood firewall, so I can access the nuts from the back of the firewall. Again, stay tuned for further progress. I am on holidays in a few weeks and then hope to get my engine test stand out from hibernation and run this thing.

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Re: McCoy BabyMac Question

Post  NEW222 on Sat Mar 10, 2018 3:42 pm

Ok. With a bit more digging online, I am now believing that the threat pitch I need is a 2-64 TPI. I now have some research to do to find one. Looks like I MAY have answered my own question. Cannot find anything locally, but when I go down to Fargo this spring, I will look around there to see if one can be found.
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Re: McCoy BabyMac Question

Post  Ken Cook on Sat Mar 10, 2018 4:00 pm

I wouldn't hesitate to press out that spraybar and reinstall a Cox assembly. That may require opening the stock hole. Just about every engine from that time frame .15 and under used a short plug. Probably the reasoning for the double gasket was to avoid the plug hitting the piston.
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Re: McCoy BabyMac Question

Post  NEW222 on Sun Apr 01, 2018 11:20 am

Just a little update. I did make a needle from a screw I found, somehow I had just one that size. I did grind it carefully on my rotary tool, and tried it. When fully threaded in, it does seal off all airflow (blowing through fuel line on nipple side), and a few turns out it does let some flow through. The only problem is that it is just a screw that bottomed out and had no easy way to adjust the needle. So, today I soldered a piece of welding rod with a bend on teh end and a piece of fuel tubing to seal it. It appears to work good. A bit stiff to turn, but the fuel tubing will keep the 'needle' in check and not undo itself. So, until I can get a few minutes to try running it, this will be it. Heading off to the US tomorrow, and will be checking Craigslist to see if I can find anything in Grand forks, either Cox stuff, or even a parts engine for this to get the real needle.
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Re: McCoy BabyMac Question

Post  NEW222 on Sun Apr 01, 2018 11:21 am

Just as a side note. The propeller on it will not be used for running. It is just installed for the picture.
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Re: McCoy BabyMac Question

Post  NEW222 on Tue Apr 03, 2018 12:27 am

A little unexpected update. While leaving for holiday, I grabbed my engine for a joke to see if I could grab a sprae 'needle'. While cruising around town, I stopped at a Hardware Hank. Took the engine in and solved a mystery. I found the screws, err needles, I was looking for. I am glad as I now know the needle thread pitch is 1-72 tpi. As a precaution, I picked up a couple spares... I am stil, hoping that my first attempt will work fine, but, I now have a spare, and I learned the proper screw size.

On another note, I also had the same luck there finding a screw with the correct pitch for the throttle stop screworking on my MDS 40 on my air car.
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Re: McCoy BabyMac Question

Post  roddie on Tue Apr 03, 2018 8:51 am

NEW222 wrote:A little unexpected update.  While leaving for holiday,  I grabbed my engine for a joke to see if I could grab a sprae 'needle'. While cruising around town, I stopped at a Hardware Hank. Took the engine in and solved a mystery. I found the screws, err needles, I was looking for.  I am glad as I now know the needle thread pitch is 1-72 tpi. As a precaution,  I picked up a couple spares... I am stil, hoping that my first attempt will work fine, but, I now have a spare, and I learned the proper screw size.

On another note, I also had the same luck there finding a screw with the correct pitch for the throttle stop screworking on my MDS 40 on my air car.

Good on you Chancey!! Thumbs Up Thumbs Up The needle that you made will likely work just fine. Nice job on that! I like the L-bend rather than a round-knob. I'd prefer that more model-engines needles were made that way.
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