Cox cylinder pre 1955 which fit small thread head

[aungmyatoo]

I bought space bug, thermal hoppers, engines & parts on ebay.
Before I knew it, I have 3 sets for space bugs & 1 thermal hopper.


except cylinders

[aungmyatoo]

one of them indeed came with cylinder but it freeze cylinder at midpoint.


Is this cylinders hard to get?
I don't want to use post 1955 cylinders as space bugs should have the older pre 1955 cylinder that fit small thread head.

[ian1954]

I am not sure that your statement about the smaller threaded glow head is correct and that all space bugs used them.

If you also look at the crankcases, you can see two types. One type has a "lip" where it touches the tank and one doesn't.

[Cribbs74]

You more than likely have a burr in your cylinder if the piston won't go past the exhaust ports.

It can be salvaged with either a round steel file or a knife blade or both. Take a magnifying glass and sight down the cylinder. You will probably see some raised steel around an exhaust port. Carefully file it away or scrape with the knife and it should be as good as new.

I did this to two thin walled cylinders last week. One of them is seen in my "running a bug jr" thread.

Early bug jrs had the small thread head later had the normal one. Both are obtainable the smaller thread one is harder to find, but not impossible.

Ron

[jjscott]

How does one remove the reed housing from the tank body on these? Mine seems good and stuck and I'm hesitant to put any sort of lever behind it and force it up.

Jim

[Cribbs74]

How does one remove the reed housing from the tank body on these? Mine seems good and stuck and I'm hesitant to put any sort of lever behind it and force it up.

Jim

That's what you are going to have to do. They are crimped in place you can see 3-4 small indents in the reed holder. Just be careful. Replace in the same orientation.

[ian1954]

I am not sure that your statement about the smaller threaded glow head is correct and that all space bugs used them.

If you also look at the crankcases, you can see two types. One type has a "lip" where it touches the tank and one doesn't.

The Space Bug was produced from 1952 to 1958 and the small cylinder head ceased production in 1956.

Apart from the two different types of crankcase, there is also the air intake. One is an "acorn type" nut and the other more "trumpet" shaped.

I expect there are timelines in production for everything.

[Cribbs74]

This whole time I had it in my brain thay we were talking about Bug Jr's !

Luckily most of the info pertains to the Space bug as well.

[aungmyatoo]

Thank everybody for the information, especially for cribb (how to salvage my cylinder) and Ian for history. So I do not need to stick to small thread diameter head and cylinder for space bugs.

[Mark Boesen]

Hello,
Be sure to look inside cylinder before you do anything and if you don't see any glaring defect you might try to just clean it up, often the cylinder can become gummed up, dirty or slightly corroded from setting around for several decades. You might want to use a Scotch-bright type scrubber (aka synthetic steel wool) and some solvent or WD-40 and cleanup bore, use plenty of oil to reassemble.

Ian had mentioned the two versions of the SB/SBJ case, sometime in '55 Thimble-Drome added a flange to the back of case to help seal gasket (from the photos it looks like you have two) these would likely (but not necessarily) have the older pre '56 cylinder. Also, the 'acorn nut' venturi, was switched to the 'flute' (?) type, I'm not sure (help Mud!) I'm gonna guess and say about the same time.

In '53 only Cox offered a 'Hop-up' kit, with new style 'horn' venturi intake, new tank with larger internal airtube and hicomp glowhead.

I think the SBJ ended in '58 and Space Bug in '59.

Mark

[Mark Boesen]

sometime in early '55 Thimble-Drome added a flange to the back of case to help seal
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