Cox 020 PeeWee rebuild questions

LooseSpinner99 Wed Sep 25, 2024 10:03 am

Hi all,
I am a novice when it comes to this process. I am looking for input about rebuilding and trying not to fall into any post holes! As a kid i would take “new” used engines apart and back together. But I’ve never started with an old frozen engine. I don’t have an ultrasonic cleaner. I plan to use an old toothbrush and airbrush cleaning brushes, like tiny bottle brush brushes. I’ve read that you can loosen up a frozen engine as follows, assuming it it because of just old caster oil: 1) soak it in fuel overnight, 2) let it sit in a pot of gently boiling water, or just use a heat gun.

For me, since I only have this one engine so far, fuel is expensive and not to be wasted . I was thinking of soaking the engine overnight in 91% isopropyl alcohol (IPA) with about 10% caster oil. That way, as I disassemble and initially remove and wipe off part, the evaporation of the IPA leaves a thin film of caster oil on each part. Any comments here good or bad? Do you think the IPA soak will work?

I’ve also read about using a special brush to “de-varnish” the piston cylinder. Frankly, I couldn’t tell you if a cylinder needed that by just looking at it. Would IPA work here or would I need to use acetone or something else? Does the piston get a similar treatment? Is this even necessary?

I hope I can get a little guidance here on the max size, weight or wing loading that would be appropriate for this little guy. I have a Cal Aero Senior Playboy kit I am starting to build, 36 inch wingspan. The kit is vintage mid 1960s and there is a free plan on Outerzone.co.uk free plan website. The plan calls for a Cox 020 TeeDee. But it looks to be very lightly built ( my assumption based on looking at the plans). From what I’ve read a TeeDee is about twice the power of a PeeWee. Any comments here would be appreciated.

Finally, I loved reading about rdw777’s 020 peewee throttle article! Very cool and if I can get this little motor going, I’d like to give that a try myself as I fly park size electric RC planes. This little motor would be perfect, even without a throttle. Has anyone tried a throttle at the air inlet side with success on this little engine?

Yes, I am long winded with lots of questions! Sorry about that and I hope that doesn’t put anyone off from commenting! Ok, I think I’m out of breath now!

Thanks in advance for any help,
LooseSpinner99

Ken Cook Wed Sep 25, 2024 10:38 am

Heat will work better then alcohol soak. Using penetrating oil or air tool oil followed by heat and more heat. One thing about a Pee Wee. DON"T PULL THE PLASTIC FUEL TUBING OFF the backplate . Heat it first and make it pliable or you run the risk of breaking the die cast nipple off of the backplate. In addition, retain your circlip on the reed as it can be considerably thinner then new rebuild kit provided circlips. The circlip is also directional, while it can go in upside down, it will only work when orientated correctly in it's groove. The return leg which runs through the center of the clip is angled and it needs to be installed so it's facing up. If installed upside down, the reed will not be able to operate as it will pinch it against the seat of the tank. The reed must rotate under the circlip which can be done carefully using a #11 blade after the clip is installed. After reed is installed, using a syringe and a piece of fuel tubing, hook the tubing up to the rear of the tank's venturi. The syringe should not be able to be withdrawn AT ALL. If it's passing air, try a drop of oil on the reed and try again. If the reed is still passing air, try and flip the reed over and try again or try another reed.

After engine assembly, I close the needle down lightly just enough to seat and pressurize the tank using the syringe. Cover the opposite fuel nipple with finger or plug and pressurize the other. You should not audibly be able to hear air passing. If you do, it's a multitude of areas. Tank to tank back, tank to crankcase, both or the needle valve assembly or needle itself. In addition, screws could be leaking which is also problematic as these use no sealers or gaskets. Typically, if you hear air exiting via the venturi screen hole, this is a direct result of the o-ring leaking air. Using drops of oil on all of the areas I mentioned will reveal bubbles showing leaks. If and that's a tough one because rarely does a engine pass the leak tests I mentioned. If the syringe immediately provides resistance during the pressure test, go play the lottery. If it does, you can bet your engine will run as good as new with little issue.

If I see a lot of varnish on the cylinder, I use 0000 that's 4 not 3 steel wool and oil. Using this with penetrating oil, kerosene or any lightweight oil works well. I don't do this dry and I do this in a circular motion . If you install the piston and it's freely moving in the cylinder without dragging, I would opt out on this. I clean this out using hot soapy water followed by towel drying and a heat gun to fully dry. Oil afterwards using air tool oil, trans fluid etc. Don't use WD-40, it's the worst choice you could make.

GallopingGhostler Wed Sep 25, 2024 11:15 am

Ken Cook wrote:One thing about a Pee Wee. DON"T PULL THE PLASTIC FUEL TUBING OFF the backplate . Heat it first and make it pliable or you run the risk of breaking the die cast nipple off of the backplate. Oil afterwards using air tool oil, trans fluid etc.

Truly an understatement, I have broken off my share of Zamac back tank nipples on both Pee Wee and .049's, over impatience and inexperience. The plastic used for the fuel pickup tubing hardens over time to almost rock hard, guaranteeing breakage unless softened.

The Zamac backs especially on the Pee Wee are harder to find, and those sold used command a heftier price than most would want to afford. The old days are gone where one could venture to a hobby shop or even a major department store like Sears, Montgomery Ward, etc. and buy such parts off the shelf. I remember those days, when in the latter 1970's, these stores liquidating their parts stock in the Honolulu stores. I purchased my share of parts on sale then.

(Shoot, I remember buying small motorcycle tires for my 1971 Honda CB100 then from these department stores, a story for another thread.)

rdw777 Wed Sep 25, 2024 11:55 am

Ken’s advice is excellent LooseSpinner…. I’ve used these a lot and get good results….If the tank/backplate/screws don’t pass the leak test in flying colors, Don’t panic there’s still some things that can be done…. fyi I use 25% nitro and usually two head gaskets on my .020’s…..

For the planes, If you like electric park flyers you’ll love .020 RC…. Gives them an attitude!… If you like to fiddle with numbers….I use two things to help predict the outcome…. Power to weight ratio and wing load….Power to weight is pretty easy….. 50 watts per lb minimum to fly…..
100 watts per pound things begin to go fast….. PeeWee’s are rated at about 26 watts…Kind of like park flyer stuff anyway right? Very Happy

For me personally, I like to keep the wing load below 2 grams per sq in of wing…. Helps keep the glide speed down (engine off) and therefore landing speeds are slower and less likely to cause damage…..

Here’s one example that’s maybe sorta close to your Playboy, An .020 powered glider….

150 sq in wing
Weight- 6.6 oz (187 g)

Power ratio = 63 watts per lb
Wing load = 1.25 grams per sq in

balogh Wed Sep 25, 2024 12:25 pm

For cylinder devarnishing I prefer using household oven cleaner i.e. cold-degreaser fluid instead of the devarnisher brush or any mechanical cleaning with steel wool , fir my fears these will unavoidably leave micro scratches on the cylinder wall, that may cause compression loss.

A cotton earbud drenched in the degreaser fluid, swiped on the cylinder wall with the piston top cranked just to cover the top of the exhaust ports will do. You do not even have to force the cylinder off the crankcase which, with old stock cylinders not having the square on the top fin for the wrench is not easy, anyway.

Once cleaned and the last earbud no longer stained by varnish, crank the piston to TDC to scrap any varnish remainder off..clean the cylinder crown, then wipe the cylinder wall with alcohol or nail polisher, oil, and you are good to go.

LooseSpinner99 Wed Sep 25, 2024 12:42 pm

Aaaaaah! This is totally awesome and exactly the kind of advice I was hoping for! I’m so glad I found this forum! I’m waiting for a few more parts before I begin. I will certainly follow this advice and let you all know how it goes!

Thank you all very much,
LooseSpinner99

LooseSpinner99 Sat Sep 28, 2024 2:20 pm

Hi Everyone,

Well, I soaked the engine in liquid wrench for two days and still no movement of the crankshaft. I took the glow plug off after day one and found significant amounts of rust, I believe in the upper cylinder and on top of the piston (see pics). None of the exterior rust was visible before soaking. I finally had to you pliers to grip the propeller plate and rotate the crankshaft just enough to uncover the exhaust ports. I had to use a lot of force and marked up the propeller plate badly. There are spares available, but I hated to do that. While the aluminum parts looked pretty good the fuel tank back plate interior surfaces also look badly corroded. I'm not sure this is salvageable. Please comment and let me know what you think. The next step is to use the oven cleaner, as it is a "lye" it might take off some of the rust so I can get a better look at it. It is the first time I am posting pictures, so I hope this comes out!

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rsv1cox Sat Sep 28, 2024 2:54 pm

Reread the first line in Ken Cooks post!! Then find, buy, borrow a heat gun. No heat gun possible? Boil in hot water with a prop on then immediately oil the top of the cylinder and the ports and turn the prop. A poor alternative to a heat gun but possible.

I finally had to you pliers No, no. Never pliers. Heat and more heat will solve your problems, but I'm afraid the damage has already been done. PM me your address and i will send you an engine.

Bob

balogh Sat Sep 28, 2024 4:23 pm

I am not sure if what I see on the piston top is rust..the piston top is covered by copper to make sure hardening during production by carburization process occurs on the piston external wall only, and the oxidized copper looks like brownish rust..I do not see the cylinder wall but a brownish discoloration may be varnish..the external wall of the piston seems clean, so I assume it is not corrosion but caked castor that keeps the moving parts stuck??

I think the backplate is OK but needs a good cleaning. The O ring on the tip of the venturi may also need to be replaced.

Ken Cook Sun Sep 29, 2024 4:56 am

Oh man the pliers, not a good choice. I don't understand what I'm seeing on the top of the piston. It looks from the picture as if I'm seeing some type of marks from a punch. You didn't stick anything down the cylinder and try and tap it out down by chance? Even forcing the engine over with a prop is not a good choice unless it begins to slowly move. Using a strap wrench, you can loosen the cylinder. The Cox piston rotates around the conrod enabling the cylinder to be loosened without twisting the conrod. Put a good quality oil like Marvel AIR TOOL oil not Mystery Oil. Heat it for at least 5 minutes. The oil should smoke heavily, then apply some more. Mind you all this is going to require good gloves because you won't be able to hold it. If you have the proper Cox wrench, you can loosen the cylinder which will lift the cylinder to enable the piston to move downward. Don't tackle this in a Hulk like manner.

LooseSpinner99 Sun Sep 29, 2024 4:19 pm

Ok, my bad. I will try the heat and oil next. Well, first I was going to try cleaning up the top of the cylinder wall and piston with oven cleaner, rinse, dry. Then I will apply oil and heat. I also am not sure at what I'm looking at that is on the top of the piston.
No, I have not tried push the piston down. I've only used the pliers and slowly rotated the crankshaft to lower the piston about 1/8 inch and stopped. No multiple rotations, up and down, or anything like that. Hopefully no damage has been done.

LooseSpinner99 Mon Sep 30, 2024 6:17 am

Response to all, Ok! Next heat. Yes, I have a heat gun, so definitely my bad. Per rsv1cox, the damage has been done. I'll still wait and see once I get the motor apart. I still hope for no damage. It may be a couple of days before I get a chance to do this.

Separate question for rdw777: Please can you tell me why you use 2 head gaskets on your 020s? I've heard of using 2 head gaskets for 049 engines in the Texaco event. I suspect it is a way to slightly reduce power and increase duration, but that is a guess.

Thanks all,
Dave

rsv1cox Mon Sep 30, 2024 7:43 am

Ken is talking about this stuff:

Cox 020 PeeWee rebuild questions P1018367

Works great on model locomotives too. Available at Walmart @ $3.00 a bottle. ..... or at least it did.

rdw777 Mon Sep 30, 2024 8:55 am

Hi Dave, It’s just a general rule of thumb on Cox engines to use one head gasket per each 10% of nitro in the fuel….25% fuel and two head gaskets works good for me ….

rsv1cox Mon Sep 30, 2024 10:10 am

LooseSpinner99 wrote:Response to all, Ok! Next heat. Yes, I have a heat gun, so definitely my bad. Per rsv1cox, the damage has been done. I'll still wait and see once I get the motor apart. I still hope for no damage. It may be a couple of days before I get a chance to do this.

Separate question for rdw777: Please can you tell me why you use 2 head gaskets on your 020s? I've heard of using 2 head gaskets for 049 engines in the Texaco event. I suspect it is a way to slightly reduce power and increase duration, but that is a guess.

Thanks all,
Dave

Cox 020 PeeWee rebuild questions Smily10

Looks like a Martian Smiley face........... with no damage. A good save as these are getting very hard to find in original condition.

Are you sure you have a .020 there and not a .049? Very well could be .020, but seems I have found the Babe Bee backplates #7 marked. Just wondering.

LooseSpinner99 Mon Sep 30, 2024 11:47 am

Got it! Thank you all for your help!

Ken Cook Mon Sep 30, 2024 12:35 pm

Using a old toothbrush and hot soapy water, you backplate will clean up fairly easy. Just insure the passages are clear such as the bottom of the needle seat where the point of the needle valve situates. Also, once the fuel pickup tube is removed, insert a fine wire or pin through the barbed hole until it hits the back of the plate. Many times, this is a area which goes unseen and can cause a lot of grief. Insert a wire or pin the filler pipes to insure all oxidation is clear.Other than that, your going to be Pee Wee'ng.

LooseSpinner99 Wed Oct 02, 2024 5:10 am

Hi All,
Success! So far. I did get the engine disassembled and yes heat was the key by far. Once I was able to get the crankshaft to rotate enough I could slip in the cylinder wrench and loosen the cylinder. It came of easier than expected. Next I bottomed the propeller screw into the crankshaft hole and in a very, very non-"HULK" like fashion tapped on the propeller screw, nothing. No movement! In the short time it took to remove the cylinder and piston, the crankcase had cooled enough that the crankshaft, again, would not turn. Heat to the rescue and a few more non-"HULK" like taps and the crankshaft slipped out! I'm starting to think the main resistance to shaft rotation was from the crankshaft bushing not the piston/cylinder contact. I can feel a small amount of endplay between the piston and the piston rod. I can't begin to estimate how much endplay. But I would guess on the order of several thousandths of an inch. Please see attached photos. So far, the only cleaning was to wipe off the oil from the parts. No attempt has been made to clean them yet. Please attached photos of the "as disassembled" condition. I'm going to use Ken's method next to clean up the backplate.

I just want to add here that I realize you guys are sharing probably years of collective knowledge and experience in helping me do this. So, thank you very much again!

Dave

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balogh Wed Oct 02, 2024 5:30 am

Nice work..the crankcase bushing will clean up with some nail polisher acetone or similar.
If you want to use the oven cold degreaser to remove castor varnish, use that on the piston, cylinder and crankshaft only....it may cause discoloration on aluminum, though..

rdw777 Wed Oct 02, 2024 10:05 am

Good progress Dave…While it’s apart I like to flatten the back of the crankcase with a piece of # 400 sandpaper with oil on a piece of glass…. It helps the tank/case gasket seal better….When you put your crankshaft and case back back together and before adding the cylinder and piston, You should be able to spin it with the prop and get several freewheel revolutions….. That’s an indication if it’s free enough to not rob power….Photo below shows a PeeWee I was working on recently and the back of the case flattened…Also, the crank a little out of focus but how polished the bearing surfaces should be on it….To polish the crank I use a prop screw with the head cut off to spin the crank chucked in a drill press and # 2000 sandpaper and oil….

Cox 020 PeeWee rebuild questions 80797b10

LooseSpinner99 Thu Oct 03, 2024 4:19 am

This is all GREAT! Clean up now in work! I will show the "after" pics of clean up and before reassembly. Also, I have to order a new propeller drive plate. I already ordered and received the rebuild kit.
Thanks,
Dave

rsv1cox Thu Oct 03, 2024 5:15 am

LooseSpinner99 wrote:This is all GREAT! Clean up now in work! I will show the "after" pics of clean up and before reassembly. Also, I have to order a new propeller drive plate. I already ordered and received the rebuild kit.
Thanks,
Dave

Your a man after my own heart Dave. Save the thing! Notice the cases lubrication groove in Robert's picture above. Stops short of the nose. Ensure this groove is clean, clean, clean. - Bob

getback Thu Oct 03, 2024 5:51 am

Look's like the piston/rod have been hammering from a to loose fit needing a reset . The piston top is bulging ? Doing a good job she is pretty gummed up but it will come clean Very Happy

balogh Thu Oct 03, 2024 6:58 am

Eric I think that bulge on the piston top is normal and a result of the old stock piston manufacture process, if you check engines made earlier than mid 70's, you will find that on all pistons, while later production pistons have flat top.

LooseSpinner99 Thu Oct 03, 2024 10:55 am

To all,
I have a cleaning question. My usual practice is to wipe things off with paper towels or Q-Tips (I know, horror of horrors!). Obviously, cleanliness is key. But is using standard Q-tips ok or should I be ordering some of those lint-free swabs?
Dave

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