O.S .55AX hard to start. - RCCanada - Canada Radio Controlled Hobby Forum
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Old 08-05-2010, 07:49 AM   #1
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O.S .55AX hard to start.

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I am having trouble getting my O.S .55 started after the first flight. It starts up perfect (by hand) when cold but after landing to fuel up (not ran empty) the thing wont start. I even try priming with throttle wide open but still no go. Give it 5 to 10 minutes and it fires right up again. I use the trim tab to shut down the engine just before it touches down. Any ideas? Also it has the pitts pipe on it if that makes any difference.
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Old 08-05-2010, 08:34 AM   #2
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Re: O.S .55AX hard to start.

Remember the K.I.S.S., method of doing things, keep it simple $%^&*#. Just kidding, remember it needs fuel, air, and ignition. I'm pretty sure you've got the air thing covered, make sure its got a steady fuel flow all the time, and that your glow driver is fully charged, or whatever powers your glow driver is fully charged. Last, but not least, how old is the glow plug? Might want to try another OS plug just to be sure.

The engine isn't running too lean is it? It almost sounds like its very hot, it gets a chance to cool down, then starts fine.

How is the engine cowl? Lots of areas for cooling air to leave the cowl. I thought I read somewhere, for every 1" of opening, there should be 3" of area that the cooling air has a place to escape.

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Old 08-05-2010, 12:34 PM   #3
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Re: O.S .55AX hard to start.

You will always have a hard time starting the enigne when it hot. I have the same issue with mine. All you need to do is riching up the engine a bit at full throtle,when you here the rpm's drop down more the 500-600 rpm then you will be ok. Make sure you use a Tach to keep track your progress while tuning.

Also give your enigne time to cool down between flights, it will make starting easyer and this will incress your engine life.

Hope this helps

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Old 08-05-2010, 03:35 PM   #4
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Re: O.S .55AX hard to start.


As mentioned above , I,m sure it,s a simple thing . the AX-55 is one of the best engines I own . It is sooooooo , simple .

If I may try this

1 ) just get it started
2 ) set the high
3 ) stop engine and close carb to start ( small openning in the barrel )
4 ) try and start again , if it doesn,t start , open the low end needle just a tade , and try again , and repeat until it starts .

This might work , works for me with no problem

Best of luck

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Old 08-05-2010, 05:55 PM   #5
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Re: O.S .55AX hard to start.

You could be experiencing an air leak once the engine warms up. Check the rear cover, head bolts and especially around the carb/front housing.
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