Hello,

I've have a Fox .35 CL engine that has been lying around since I was 14 years old. When I was a kid I was never able to start it and it has been gather dust and crud for the past 25+ years. Today I cleaned it up and it looks to be in pretty good shape -- all things considered. It has a lot of compression and feels smooth when you turn it over.

My questions are how do you break in an old engine like this? Also, it doesn't have a muffler -- do I need one to bench run it (I have hearing protectors )?

TIA for your help.

Cheers!

Galen

Galen Run it! Make sure the spray bar is pointing at an angle towards the crank and to the rear of the motor sorta like
(<) Front of the motor (\) Spray bar. Turn your needle valve in and then back it out about 2 turns. use a 10 X 6 to break it in, get it running and tweak the needle so it is just at a transition between two cycle and 4 cycle. If you point the engine up towards the sky it should then 2 cycle this is an ideal Fox setting as well the same setting all of us stunt pilots and sports use to do in U/C.
Now for a Muffler years ago there was a muffler called the Peace Pipe. Some of us got lucky and got a few. If you have no problem with noise then by all means run it without.

Now do you remember what a control line tank looks like? LOL you can use a 4 Oz or 3 or 2 Oz clunk as well. So don't think because it's a Ukie you have to use an old Veco or Perfect Tank. Now I'm showing my age : ).

Hope this helps.

The old Fox .35 is a plain-bearing (not ball bearing) engine with an iron piston running in a Meehanite cylinder. You should break it in using fuel that has a high oil content (25-30%) and uses mostly castor oil. I broke all of mine in using Fox Superfuel (29% Castor / 5% Nitro) which was originally designed specifically for this engine, if memory serves me correctly. Fox still manufactures Superfuel and it should be available through your local hobby shop.

As far as breaking one in, it is best to run it on the bench for 30 to 45 minutes running time at a fairly rich setting (rich 4-cycle). Run it for 3 to 5 minutes then let it cool for 15 to 20 minutes then run it again. They do take a long time to break in by today's standards but it will last for a long, long time if run on Superfuel. I've yet to wear one out.

There should be an aftermarket muffler available to fit the Fox .35. One using a screw-type strap would work fine as it is quite noisy without the muffler. Would probably upset the neighbors to listen to that thing running for several hours!

As CurtD says, use lots of all castor oil and don't even think about synthetics. The Fox liner is a leaded steel and is softer than most other similar engines used. That's why Fox made their Superfuel. If you want to make your own fuel then shoot for 30% castor.
If you've had the spray bar out then check to see if it has 2 holes. These aren't exactly 180 degrees apart and should be fitted so that when you look down the venturi you can't see either hole (in other words both holes are pointing very slightly down towards the crankshaft).
Make your first couple of runs absolutely slobbering rich...you may even need to keep the plug connected. Don't let it run in a 2 stroke for at least 30 or 40 minutes and even then I'd only allow it to just break out of a 4 stroke. Rich is good for these engines

Boy! You Aussie's run alot of castor! I was running these engines on K & B 100 for over thirty years. K & B 100 was around 8% nitro and about 22% Castor Maybe. Never knew exactly how much castor was in that stuff, just know it sure was a slimer when it got done. Now I use red max 15% & 10% Nitro 20% Caster and they still run just fine.
With 42+ Years running all my U/C engines, I still run them breaking to two stroke on elevation and they still all run just peachy!

Fox 36X and Combat Specials as well as Enya and ST's all ran on K & B 1000 now they also run on Red Max 15%.

O & R an McCoy's as well McCoy/Tester's are all running on 10%Nitro 20% Caster.

Anyhow glad to hear the Aussie's are still flying U/C take care guys.

good info in posts above. one thing i have found is with the stock fox NVA, the needle often needs to be out 5-6 turns for a good rich setting. two turns out, and you will probably not get it to do much more than run out the prime!

The stunters are presently running 25% oil in the OS LA series of engines. The reason for so much oil is that it promotes good 2-4-2 breaks. That is because it pollutes the incoming charge better than unburned fuel because it is thicker and doesn't burned, thus an engine will 4-cycle at a leaner setting with more oil, and break out of it quickly. I don't think the liners are any softer than other manufactures, all of these old steel lapped engines used soft steel on the liners. McCoy were probably softer than Fox. I have used Morgan's Coolpower with 4 oz of castor oil added with no problem on my Fox .35. Though this was only for several tanks, the compression does not seem any worse. I am now running 26% synthetic-castor mix. It breaks into a two cycle much crisper now.
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