Rotax 503 Tear Down!

[@b01tact10n]

The 503 Rotax is one of the most reliable engines I know of I love your comments towards this powerhouse of an engine 😁 That's great work! You got great skills!

[@FourthWayRanch]

does the UL have metal rings for head gaskets? the skidoo version only seems to have the o ring seals

[@hogsnplanes]

The 582 has O-rings.

[@keithschneider6348]

They have a el ring for the top piston ring.

[@FourthWayRanch]

how did you get the wrist pin out? skidoo manual says it needs a puller? I was able to push it out by hand after all, good thing I decided to pull this ebay skidoo engine apart, the crank bearings were shot, now I have to figure out how to rebuild this crank

[@hogsnplanes]

There are shops that do those cranks, usually performance shops.

[@edpaine7982]

Great video, I'm tearing one of my 503s apart right now. No videos showing the dissasembly of magneto end, specifically the crankshaft locking pin? Could use any help..

[@hogsnplanes]

The lock tab for the crank is actually on the factory puller. It is 2 piece. A back plate with the tab that bolts to the mag on the pulley studs and the actual puller screws into it.

[@FourthWayRanch]

how do they make the mating surface for the gearbox so smooth on the UL crankcases? is there a ring or washer on there? I got my skidoo 503 machined and filled the crank half gaps with gasket glue and it seems to not be leaking. if you have 503UL intake manifolds around can you tell me the ID? I think I need to put 36mm carbs on my engine, the 34mm skidoo carbs don't seem to want to push the prop past 4000 rpm, I wonder if I need the UL manifolds too

[@hogsnplanes]

The 503 SkiDoo engine is actually quite different from the UL Engine, the crankshaft bearings were improved, intake ports changed, timing altered and even the wrist pin bearings were changed to cageless. The 2 engines are only the same on the outside. Bing carbs were also used on the UL engines. I never recommend using a snowmobile engine in a UL.

[@FourthWayRanch]

@@hogsnplanes my sled engine has cageless bearings. The timing is the same as the UL too. It's out of a 97 forumla SL. I ordered a new PTO side bearing for the crank OEM from skidoo too, I think it's the same. Maybe the differences were from earler engines. I've got the skidoo shop manual too, I used it for the rebuild. I can get brand new mikuni VM36 mm carbs for 120 bucks from summit racing instead of 450 for the bings...what's the difference, I know how to jet a carb.

[@hogsnplanes]

@@FourthWayRanch People have used the Mik's with no trouble but the Bings again were designed with aircraft in mind. Porting of the Snowmobile engine like I said is different so setting her up I would go stock settings. The max RPM is determined by the propeller pitch.

[@rc300xs]

Would reliability be the same? Hope to see more of this upgrade.

[@jesseperez7253]

What engine oil do you use or recommend for this rotax 503?

[@hogsnplanes]

Shell snowmobile oil is the best I find. Rotax recommends it as well.

[@jesseperez7253]

Awsome, Thank You

[@jesseperez7253]

Was watching all your videos of your snowbird build all the way to your most recent videos, it's been like 10 years, how many hours have you put on that rotax 503, and how reliable?

[@hogsnplanes]

@@jesseperez7253 I put well over 100 hours on it when a suspected bearing failure occurred. That said there was no time log on it when I bought it used so the total time on the crankshaft is unknown plus it was poorly stored prior to resael. Otherwise it was a very reliable engine and it got me home when I detected a small vibration that was probably a crank bearing beginning to fail.

[@siTTinLo]

Great vid, I'm tearing down the same motor that's in my ski doo snowmobile, and I have been wondering, how do the lower end bearings and crank get lubricated? Is there crank case oil in there that needs to be replaced or does the oil injection pump lubricate the lower end as well? If so, I don't see how...

[@hogsnplanes]

2 stroke engines either have oil injection or oil mixed with the gasoline. The air/fuel/oil mixture goes through the bottom end via intake ports or reeds before reaching the combustion chamber.

[@overback2328]

Why do you keep your shop so clean? You should throw a bunch a stuff around and make it look messy. I bought your video several years ago. It taught me a lot. Thank you.

[@hogsnplanes]

Over & Back A clean shop is easy to work in.

[@oscarperezgonzalez9203]

Can i install a torque converter in those i have one i want to install in a dune buggy

[@hogsnplanes]

This one is set up for aircraft, Snowmobile version has a belt drive and centrifugal clutch.

[@oscarperezgonzalez9203]

Ok nice cause i aquire one from a snowmobile i want to install it in a odyssey fl350 buggy do i need the harness

[@oscarperezgonzalez9203]

How can i tell if i have the aircraft version or snowmobile

[@hogsnplanes]

@@oscarperezgonzalez9203 Not if your good at wiring, would help though.

[@hogsnplanes]

@@oscarperezgonzalez9203 Aircraft has a different type serial number and threaded gearbox mounts on the PTO side of the crank case.

[@hogsnplanes]

I am thinking yes. Project Airplane Diet! :)

[@billcallahan9303]

That workbench looks like mine now that a friend has taken it over. It was spotless. I murdered him last week & am now a fugitive from the law.

[@hogsnplanes]

Bill Callahan 😂

[@Happygrowercbris420]

Yah right

[@MrJohnm1965]

Great comment bill!!!!

[@hogsnplanes]

No, The Continental beats any 2 stroke hands down, Just too damn heavy. More to come.

[@hogsnplanes]

May lose 5 mph, not too worried about it.

[@thomasrivers185]

the crank is junk... bearing chirp, nice!

[@hogsnplanes]

+Thomas Rivers Yup, needs replacement.

[@unitderrickhand]

I bet your performance wont be much difference. With losing 70 lbs you can afford to lose some HP.