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Lazair.com • View topic - Engine rebuild

Engine rebuild

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Postby bdiedenhofen » Thu Dec 03, 2009 8:16 am

Hi Guys,

Just tearing my engines down for inspection. I've discovered that I need new bearings all around after 120hrs. It's been several years since the last rebuild, and the plane is outside for the summer. Just a "heads up" for those in a similar situation. Even though it may run well, the bearings may require inspection.

I'm glad it's such an easy task. I had them both apart in under an hour.

I'm curious though if anyone has had any luck finding a shop that can replace the lower connecting rod bearing on the crankshaft? Visually it appears ok, but it's really hard to tell without actually removing the bearing. That's impossible to do without the proper tools etc. I know of a shop in Quebec that can replace the 447, 503, 582 bearings but I don't know if they can do the 185. Has anyone replaced theirs, or do you think it's necessary?

Thanks,
Brian D.
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Postby barrystrs » Thu Dec 03, 2009 5:49 pm

I don't know where you would send the crank to get the rod brgs changed. If I remember right the bearing comes as a kit with the rod, bearing, and pin since it takes all 3 parts to make a brg. How could you tell that the main brgs need to be changed? Were they rusted or brinelled? Barry
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Postby bdiedenhofen » Fri Dec 04, 2009 9:24 am

Main bearings were easy to tell, they ran pretty rough. It's hard to be sure with the engine in one piece, but I could hear a slight noise when I tuned the shaft by hand. Once the engine was open, they were easy to inspect. One engine was better than the other, but still not entirely smooth. The poorer engine was showing signs of pitting and very rough rolling. In the process I also discovered that one oil seal was also torn. Not visible until the shaft was pulled.
This is all due to intermittent use, and being stored outside. I'll make up some covers for the future. That should help a bit. But anyone who uses their plane for 25 or so hours per year and stores outside should probably consider a tear down every five years, just in case.
I put the new bearings and seals into one engine last night and had it all reassembled in just over an hour. So it's not a real hardship and the cost of bearings is cheap enough.
I can see a bit of the pins on the main crank bearing through the lubrication slit, and they still appear ok. The pins on the wrist pin bearing were definately pitting, hence my concern.
Just as an FYI, my 447 in my other plane had pitted pins on the wrist pin bearing which failed in flight. Made a big mess of the piston and the engine stopped of course. For a couple of bucks and a few hours of time it's worth replacing that bearing periodically too.
Brian D.
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Postby Shannon » Sat Dec 05, 2009 8:07 am

Brian I've rebuilt 4 low time engines that were ruined by outdoor exposure. One set had 4hrs TT. Exactly as you found bearings were ruined with the exception of the main rod bearings. No longer than it takes to install and remove engines I wouldn't let them sit exposed for any long period even under covers. Remember to plug the mufflers as well as the carbs when engine covers are used. Make sure the compression releases are not open too.

The engines are capable of many many hours on the crank assemblies. When the time comes it's probably better to replace the entire crank assembly or better yet the entire engine.
Shannon
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Postby bdiedenhofen » Mon Dec 07, 2009 3:08 pm

Good advice, thanks Shannon.
If I know that I'll be away from the plane for any length of time in the future I will take the engines home for dry storage.
Brian D.
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Postby Chappy » Mon Dec 07, 2009 8:56 pm

Brian,

How about Steve Beatty? He does crank-rod bearing replacements on all the larger Rotax engines, maybe does the 185 too.

AIRSCREW PERFORMANCE, Glendale, AZ USA • Telephone: 623-842-3902

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Postby bdiedenhofen » Tue Dec 08, 2009 2:58 pm

Good to know.
Thanks,
Brian
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Postby lazairiii » Tue Dec 08, 2009 3:35 pm

Brian,

I'm doing rebuilds on 185's as well if you're interested.

If all you need is for the old bearings to be removed and then replaced, just ship me the cranks and I'll pull your old bearing and replace them with brand new ones. I have a supply of bearings on my shelf. E-mail me off line and we can discuss it.

gcurtis@aspenpress.com

George C.
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