Rotax Rebuild

Share your thoughts, photos and general help to all builders

Postby gdewsbury » Sat Feb 04, 2006 6:08 pm

Couldn't get a side by each with the old crank. Tossed it out after a couple years.
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Postby gdewsbury » Sat Feb 04, 2006 6:09 pm

Say thanks to Jim Tone for taking pictures will I was in shop doing a little welding.
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Postby gdewsbury » Sat Feb 04, 2006 6:20 pm

I certainly wouldn’t get a new crank unless there is something wrong with the one you have, but I personally wouldn't put the drill rod back in either. Just my opinion. Keep in mind that the changes are most likely as a result of performance issues for the water pump. 90 GPM water pump is a lot more sever application than turning a prop.

Cheers
Glen
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Postby Shannon » Sun Feb 05, 2006 12:26 pm

There you go Karl. Great shot of the sharp taper on a small PTO end crank.
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Postby flyalaz » Mon Feb 06, 2006 12:00 am

Clear as day. All this should help in the future as well.
I measured the old bearings and compared them to the new, and all had the same dims. When I first popped off the mag side bearing, there was no shim in place, so I added the shims I needed to the fwd side and assembled everything on the crank. It was only after setting the crank in the rear case half that I saw the crank lobe fouling on the casing. I had seen some scuff marks on the housing, but nothing was apparent on the face of the crank lobe. I guess under load it pulled forward off the casing just enough to prevent it from doing serious damage. You never know what you'll find when you open an engine!
So, once again I have to remove bearings and go to Wildfire to get some shims. I don't have any .983" diameter. All I have are the .788" diameter shims. What a pain in the butt. At least the drive is only 20 minutes from here.
If you're gonna do it, do it right.
I'll also post the layout from the manual, This will give all the info they could possibly need on parts and numbers.

Cheers,

Karl
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Postby flyalaz » Mon Feb 06, 2006 7:04 pm

Picked up the shims today. After removing the bearing, I put two shims for a total of .024" on the rear, and one shim of .012" on the front. I measured .038" total between the cases, so my .002" free play fits in the specs.
Note: Without any shim on the rear crank lobe, fitting even the rotax puller under the bearing was a pain.
Crankcase is now cooling on my table, and I will put the rest of it back together tonight. Should be able to do the timing before I hit the sack!

Karl
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Postby flyalaz » Tue Feb 07, 2006 12:29 am

Finally finished! Glad I don't have to replace the big stuff often. What makes all the difference in the world is having the right tools, and luckily, there aren't too many that are needed. Thanks to Shannon, Glen and George for all the help and tips.

Next project: Retrofitting a couple of new spinners on already drilled backplates.
Should be an interesting test of patience! Time to start a new string.

Blue skies,

Karl
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Postby lazairiii » Wed Feb 08, 2006 3:09 pm

Very nice job Karl! Now you can handle this type of repair at any time without fear. Thank you for posting the pics too. This really helps those of us that are visual types.

Super job,
George Curtis
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Postby art » Thu Feb 09, 2006 12:17 am

Karl, were did you get the prop covers in your last photo.
Thanks Art
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Postby flyalaz » Thu Feb 09, 2006 1:41 pm

Hi Art,

I make these little goodies. If you check: Karl's covers , you should see some of my stuff. These particular covers are made from four thicknesses of leather. I now use top grade outdoor vinyl.

Karl
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