Rotax 503UL Crankshaft Truing

How I adjust the crankshaft to remove excessive run out on 503UL

[@aerocam2]

Very informative. We don’t tell you enough, but we really appreciate the time you take, and the expertise to share this knowledge. Thank you so much!!!!

[@RotacRepair]

I really appreciate that! It’s an honour for me to pass the knowledge along.

[@gregosborn8284]

Thanks for doing this video. You have a lot of knowledge and experience. We are fortunate to have you sharing with us. Take care.

[@RotacRepair]

Thank you, you’re too kind. Happy flying!

[@donsipes]

Just found this channel. Excellent tutorial. I have some vintage Rotax sled engines to rebuild. I'll be putting this to use for sure. THANKS

[@RotacRepair]

Thank you! Hopefully you are a subscriber now. I’ve have seen the run out on some crankshaft videos on KZbin. If it’s within a few thousands their very happy with themselves, however that’s not nearly good enough for aircraft usage.

[@edsmachine93]

Nice work. Good job. Very tedious job.👍 Thanks for sharing. Have a great day.

[@RotacRepair]

Happy to pass the knowledge and experience along!

[@challenger2aircraftadventures]

I've trued motorcycle engine cranks in nearly the exact same way. Thanks for the great video, and Cheers from Winnipeg.

[@RotacRepair]

Thanks for watching!

[@Euronasa]

That was simply awesome! Thank you so much for sharing of your abundant knowledge! Greetings from Norway:) I will try doing this on my 1986 Lynx 5900 GLX 503 snowmobile engine. I`ve seen videos of truing while supporting the two center bearings and then working on one side at a time. That was how i intended to do this. Now I will atleast take my readings like you do and compare the two. I think the Rotax way is the best for distributing the errors across the bearings which is what really counts at the end of the day I would guess. Sidenote: What I found interesting with my crank is that the clearance is not the same for all my bearings. The two center ones are C3 the rest is C4 aka more sloppy than the center ones. I also have the older version with big mag bearing and the rest smaller.

[@RotacRepair]

Thank you for your kind comment and intelligent thought on distributing the errors across all the bearings. . I believe the C4 clearance bearing are required due to the wobble of the outer crankshaft flywheels from using the centre support truing method. Same flywheel wobble results when supporting on centres from each end. Please let me know your results of the “Center support” verses “the Rotax way”.

[@DadsShop1]

Thanks this explains alot , Excellent job

[@RotacRepair]

Glad it was helpful!

[@eipperone5643]

Thank you, just what I wanted to see.

[@RotacRepair]

Perfect, I don’t think there’s a video like it anywhere on the net.

[@KirillNeduzhiy]

Hi John, thanks once again for this great and very informative video and I appreciate all the effort you are puting in making all the videos, I know it's not that easy and that it takes a lot of time so thanks for sharing your knowledge on here! Did some 277 and 503 overhauls myself and operate 2 of them. Quick question: there was an interesting video a while ago that you made about another Rotax one cylinder (not sure whether it was the 185 or some other) where you had to source a part and wanted to make a follow-up if I recall correctly, how did the story turn out? Would be interesting, thanks. Cheers from Germany and all the best!

[@RotacRepair]

Thank you for the kind comments. Yes the video thing is time consuming however I do enjoy passing the knowledge and experience on.

[@gideonbeukes3847]

Great video Thanks

[@RotacRepair]

Glad you enjoyed it. Best regards John

[@clearprop]

Another very interesting and educational video, John - really enjoyed this. I just wanted to ask though - if each of your 'taps' can alter things, how come the environment within a running engine doesn't knock everything out of alignment again? I appreciate that it does creep out over time (hence the need to true the crankshaft) but I would expect the power stroke in the engine to make a real mess of the alignment.

[@RotacRepair]

Excellent point, I believe if the engine runs smoothly and isn’t mishandled during the installation of the drive system or electric start it should stay straight.

[@clearprop]

@@RotacRepair I guess the peak g loading of the power stroke isn't going to match that of the brass hammer. Interesting stuff - thanks again. 👍

[@Euronasa]

I have seen that some weld their cranks to avoid risking that.

[@clearprop]

​@@Euronasa Which then makes me wonder whether the heat involved in the weld may cause its own issues... Seems a good idea in principle though.

[@jenserikfilipsson5910]

Is it posible to find the service instruktion for the crank that you show in the begining of the video? And thank you for a good and interesting video

[@RotacRepair]

This document is available at rotax-owner.com for free download. On there home page select, "Support/Bulletins". next in "simple search" select "All 2 stroke service instruction documents. Hit search, follow down left side of page. Select SI-22-1994 Thanks for your comment, Happy flying

[@grantunderhill6451]

Where are you located?

[@RotacRepair]

@@grantunderhill6451 I’m located in Whitby Ontario Canada

[@grantunderhill6451]

@ I have a brother who lives in Brooklyn and 4 nieces and nephews that live there,lol. I need to pick your brain about the 503 Rotax engine .i ordered a gasket kit and new rings since I have the motor apart,got the parts from Royal Distributing today but my 503 has o-ring head gaskets and in this kit they are metal ,before I call and order another kit I would like to make sure what I’m talking about ,so was wondering if you happened to know when the rotax went to the orings. If not maybe you know someone I could contact up your way that is knowledgeable about the 80-90ies engines. If you’d be willing to talk on the phone for a few minutes some evening maybe we could set something up ,I have a few more questions you could probably answer.The fellow on the phone at Royal was great but he’s a parts guy not a mechanic.

[@RotacRepair]

@ I’m not a sled guy, your engine is different than the aircraft version. However I believe you’re looking for 1993-2003 skidoo series 503, gaskets #09-710196. Or just 710196. I think it’s a fit everything sled kit with the aluminum and the o rings.