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Author Topic: changing bearings in F2D engines  (Read 2317 times)
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« on: April 22, 2014, 08:43:53 AM »

I have changed bearings in other types of engines & have never had any problems. I had a midair & hit the other guys muffler/ engine mounts with my engine. The bearings felt a bit rough afterwards so I have pulled the engine apart & fitted new Koyo bearings. The shaft spins freely but there is not discernable end float with a cold crankcase. My other engines have endfloat.. Is this a problem ?
I fitted the rear race to the shaft then heated the case & dropped it over the shaft, fitted the front race & retaining ring..
why no end float?
There was endfloat with the old bearings..
Cheers
Ian
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Yaroslav Melnikov
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« Reply #1 on: April 29, 2014, 07:03:34 PM »

The problem is the bearing seat diameter quite varies as well as the bearing outer rings diameter and the radial balls clearance due to some tolerance while the production. While assembling the engines the makers pick the bearing that better fit to a particular bearing seat. We are talking about a few microns here, but a few micron here-few microns there and the problem comes up. So it might happen in your engine the seat size is relatively small so once the aluminum gets cold after the bearing hot pressed, the crank case bearing's seat shrinks a bit shrinking the bearing outer ring too, thus reducing the balls radial play to some minimum number. At this point I would suggest to use any other bearing with more radial play, you can feel it easily - just play with a few bearing and you'll see the difference. The other solution might be to lap the bearing seat, but you've got to have a special tool and some skill. And also don't forget to slightly knock the crankshaft with light hammer from both sides, do that kind of multiple knocks - doing this you are align both nose and rear bearings to get the best axial play.

On some engines in my fleet I have to change rear bearings 2-5 times before I get desirable axial play.
You probably can leave it like that, but the engine might not be fast enough
« Last Edit: April 29, 2014, 07:11:05 PM by Yaroslav Melnikov » Logged
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