Cox Fuel Hose and Tank gaskets

Roddie,
Thanks for your detailed answer. Yea, I know a lot about them along with info you mentioned, but didn't know the screw sizes off hand. I have a friend that owns a Bolt company and I will see if they have anything before I order . Thanks again !
Steve

A pack of assorted stainless steel pan head 2-56 screws with nuts can be gotten at Radio Shack. They are usually in a large drawer bin on the sales floor. They'll also have #2 washers.

* 2-56 Round-Head Machine Screws (42-Pack)
* Model: 64-3010
* Catalog #: 64-3010
* $2.09

What I'm mostly referring to in my answer is the Cox Bee type reed valve engines with the built-on fuel tank.

Unfortunately, these screws are all slot drives, slip, puncture, and cuss drives, SPC drives. They fit mounting tabs without scratching the tank wall, and they fit tank backplates too. For added safety against cracking or deforming the internal boss of the tank backplates, I believe the #2 washers will fit inside the recess. For final assembly, that washer makes a good seal against air leaks with a little RTV smeared on the underside of it, and under the screw head too. Micro cracks in this area are one of the hair pullers of tanked Cox engines. Many of the maddening problems of erratic running tanked reed engines are pesky air leaks.

Another one is that the threads in the crankcase are not always deep enough, either to maintain a good grip on a screw, or other times it'll give a false impression that a slightly longer screw is tight... when in fact, it's only run out of threads, leaving both the crankcase and backplate leaky. This is the #1 reason you should get a 2-56 plug tap, or flatten the tip of a taper tap. The holes are plenty deep enough, just not threaded all the way down. This makes the backplate feel tight before the screws are actually in all the way. I've extended the threads up to 5-8 turns deeper on some engines.

There are many other reasons for performance killing air and fuel leaks there too. The flat washer Roddie mentions sealing the venturi tube to the backplate's air inlet will cause it to possibly run well at first and then sputter and change speed when the fuel level drops and uncovers this seal. The head pressure goes haywire. Though at first glance it looks like a worn out flattened o-ring, it's not toroidal and if you try to force a small o-ring to work, it may deform the already super bitchy backplate. Especially the plastic ones. People have made replacements with varying success... silicon fuel line slices, latex surgical tube lots of experiments have been done. But give it a try, maybe you'll nail it. Maybe a thin wall bicycle innertube. Probably been done.

Tank to crankcase gaskets; I've done it with heavy duty aluminum foil and RTV. RTV alone works too, but it's just a mess if you have to take it apart in the field for a quick fix of whatever else starts leaking. Paper or some other gasket material from the auto parts store might be a good bet.

You can get pretty crafty with internal pickup tubes. Aluminum secured with a tight collar of fuel tube to affix it to the nipple. Make sure the pickup opening is sliced at an angle so it doesn't suck up to the side.

Copper head gaskets, buy 'em. Buy a sack full of them. eBay sources may vary in thickness and metallurgy, but you can work around that and they'll usually be fine. Norvel .049 and .061s have the same ID/OD, but I haven't compared the thickness. Old ones can be annealed with a not too aggressive torch to bring back their malleability, but won't fatten them up after they're crushed and thinner. But it will help prevent working loose during a run I watched one of our members who's name I won't mention vaporize a Tee Dee .010 gasket in about a half a second with my propane torch, Lol. Personally, I like to support Cox International and Ex Model Engines(Bernie and Matt) and buy things like this from them. They have both been very good to us with high-class customer service, not hesitating to work together for our sake, and quite frankly we need each other. So browse their sites and balance frustrating trouble and time spent with a few bucks. Start a Cuss Jar, Lol, damn, I just thought of that. Only put money in it when your cussing is directed at a failed fix for a Cox Engine.

Glow plugs; Both of them sell the interchangeable Merlin drop-in and clamp ring head types. Unless you're a purist and only want OEM parts, these are the best replacements for low and high compression. They need more washers to tame the compression, even in the high comp. applications.
* Clamp ring head with glow plug - https://coxengines.ca/cox-.049-glow-plug-adapter-insert-style.html
* Replacement glow plugs can be bought for $5.95.
The spring loaded sub-c pocket glow igniters like many of us use on our stunt(and other standard plug) engines will fit these too.

Reeds can be made out of many materials. Old floppy disk material used to be popular. I have not tried it, I just buy a little sack full of the Mylar(Not Teflon) oval reeds. Depending on the type of reed retainer, some shapes and thicknesses work better than others. I have some medicine patch peel-off plastic backing that I think would work well, but again, never tried it.

Starter springs are a must for me. I love the anti-reverse cam-ring type starter spring. And stay far away from old plastic props. Don't let anybody tell you that boiling them will rejuvenate them either.

That's about all I have for now, but stay tuned. And here's a good read:
https://www.coxengineforum.com/t753-the-revised-2011-gibeault-mouse-race-program#10434

Hope that helps,
Rusty