Starting a ROTAX 503

Penguin

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John:
They are very sensitive to plugs. Have you got new plugs in with the correct gap (.018" I believe)? Gap 'em - don't use 'em out of the box!
 

Kevin_Richey

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The Vancraft Rotor Lightning had the 503 mounted upside down. We had fouled plugs and hard starting all the time on ours. Had to pull start many times before it would fire up. Once warmed up, it'd start fairly easily.

The choke levers on that plugs-down 503 didn't work as well as the plunger primer I have now on the upright 503 on the Sport Copter Lightning.
 

drtomcor

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Springfield, mo
Thanks for the feedback, IF one were to run without the prop, do you balance each carb's idle speed by ear, counting screw turns, or a vacuum gauge?

Thanks,

Tom C
 

Friendly

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Rotax had a video on how to Sycn the Carbs. it is better to watch the video. but someone may be able to tell you step by step the process. Inverted engines tend to have the excess oil settle in the bottom of the cyclinder which is the top since it is inverted. The plugs being the lowest place become oil fouled before you do anything just by gravity feeding the oil or gas to the plug.
 

Bill

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I cheat.

I have a DCDI 503 with dual enrichment plungers (chokes) that flat refuses to start when the OAT is 60 degrees or less. Having tried all the common recommended procedures, I cheat by removing the rubber primer port cap on one of the carbs and give it a 2 second squirt of automobile starter fluid (keep the throttle in the closed position so the fluid does not go forward into the air filter and get the can that contains lubricant) Put the plug back on and pull the rope two or three times, then go have fun.

I wanted to install a primer, but am just too lazy to do the work, so I cheat. If you do this, it would probably be best to order a couple of spare rubber caps incase you loose one or it wears out: CPS # 860-610 Primer Port Rubber Cap. Also, the can’s red spray tube won’t exactly fit on the fitting and will make a mess if you aren’t careful. I siliconed on a short adapter hose that fits over the primer port fitting.

Bill :)
 

Jpipe

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Hey Guys,

Thanks for all your input.

I thought about priming the carb before starting and the easiest way of accomplishing this.
So I thought that if I blew into the over flow vents, that would force gas into the carb.
IT WORKED, started on second pull!!

I am so happy that I can get it started easily now.

 

Jpipe

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Yes, New plugs and gapped.
Learned to prime by blowing into the over flow vents and she started straight up.
Thanks

John
 

Dale Young

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My old single ignition/dual carb 503 started every time on the 1st or 2nd pull. I HAD to pump the primer knob 3 times AFTER fuel became visible in the lines.
Then when it started, it would die in a couple of seconds If I didn't continue to slowly pump the primer knob in and out for 30-45 seconds of warmup.
Ditto! Same EXACT experience here.
 

Jpipe

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It was in the 50's,when I tried this.
John
 

Alan Uhr

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Rotax 503

Rotax 503

Jpipe, I see your engine is mounted up side down. On my 1st Gyro I had it mounted that way. I live in Florida. If I didn't fly for a week, the gas/oil mix would wash down off the cylinder walls onto the spark plugs. This in effect would wet the plugs in a puddle of raw gas. Raw gas in liquid state doesn't burn. I removed the plugs and shook them out and put them back in. I also used a squeeze bulb from one of the ultralight parts houses. Not from a boat place. I pumped the squeezed bulb until it was hard, pulled the starter rope threw 3 times. Put the ignition on, put the choke on and start the engine. It never failed to start within 3 pulls. This has always worked for me. Also, when you get to 100 hours on your engine, replace the fuel pump. They are cheap and the have failed me 2 times within 150 hours. I have replace them at 100 hours and have never had another failure. The diaphrgm goes bad. It will get your attention if your in the air.
Hope this also helps. Alan Uhr Old home of the SuperGyro.
 

Redbaron

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Yes, New plugs and gapped.
Learned to prime by blowing into the over flow vents and she started straight up.
Thanks

John
I went flying today john and tried your method of priming. I think I will do away with the plunger primer. Yeah it worked that good.
 

Captainkrik

Newbie
Joined
Jul 7, 2013
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Sacramento
Difficult to start

Difficult to start

I had a similar problem with a 503 DCDI after a friend gapped my plugs for me. He gapped them at .035 and the engine was very difficult to start. Once running it was fine. I regapped to .016 and problem solved.

Hope this helps.
 
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