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Fuel for Cox .049

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Old 02-15-2013, 08:04 PM
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Vinyl Cafe
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Default Fuel for Cox .049

Hey everyone, I have been using Sig Champion 2 stroke 15% nitro with 20% oil (1/2 castor and 1/2 synthetic) for my Cox .049 surestart engine. But lately I can't get it to start, I have never had any real problems with it even though the needle valve doesn't really work. I put a little Cox Lube after run oil in it after every flight, would that damage it anyway? and I always made sure all the fuel was out of the engine. Your help is appreciated.
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Old 02-15-2013, 09:56 PM
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Default RE: Fuel for Cox .049

It's pretty easy to rule out fuel feed trouble if you can choke the engine and crank the engine enough to flood the engine.
Pull the glow plug and verify that you have a nice orange glow. You can also see the glow through the exhaust ports while the glow plug is on the engine.
With any decent compression and the presence of fuel vapor and a good glowing plug the engine should "bump" when you grab the prop and rotate the piston through TDC.
If the glow plug element is white, it is used up. This usually causes the engine to only run for as long as the battery is connected.
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Old 02-16-2013, 09:56 AM
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Default RE: Fuel for Cox .049

Ok, thanks for your help. So that Sig Champion fuel is okay for this engine?
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Old 02-16-2013, 11:20 AM
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Default RE: Fuel for Cox .049

That's a good base fuel. I would dump in an extra oz of Sig castor oil per quart of fuel because the "economics" of doing that make sense for me.
Make sure you keep the ball socket from developing any slop. You can unscrew the cylinder to check the ballsocket without removing the engine from the plane, so it's pretty easy to check as often as you like.
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Old 02-16-2013, 07:05 PM
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Default RE: Fuel for Cox .049

Ok, just one more question, I have an old Cox Crusader control line model and I want to use my surestart in it but I would have to take off the little tube on the back of it (not sure what that's for) so it will fit. So, will my engine still run without it? (You can see what I mean in the pic)
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Old 02-16-2013, 07:24 PM
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Default RE: Fuel for Cox .049

That is the air intake and it supports the needle valve somewhat.
Plan your mounting accordingly to allow air to get into the engine.
How much line is the Crusader supposed to be able to fly on...?
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Old 02-16-2013, 07:25 PM
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Default RE: Fuel for Cox .049

Quote:
ORIGINAL: Vinyl Cafe

.......So, will my engine still run without it? (You can see what I mean in the pic)
It will run just as well or better. The tube is called a choke tube - by blocking the end with your finger and flipping the engine, you could pull fuel into the engine. If the engine was mounted in a cowled fuselage, priming the exhaust ports could sometimes be difficult, so the tube was added.

The needle will be unsupported, so you may or may not want to shorten it to help protect it from being bent. Secondly, after removing the choke tube, you need to ensure that the backplate screws don't bottom out before tightening up - the ends may need to be filed back.
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Old 02-16-2013, 07:58 PM
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Default RE: Fuel for Cox .049

Ok, thanks for the help. I read through the old fuel soaked manual and it reccomends 10-25 feet of line for flying.
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