Bearing play?

[Minority]

Hi everybody,

A quick question for the experts. How do you tell if your Magneto flange bearing is worn?
When I was in the process of taking out my crankshaft (I'm going to match the casing to the transfer ports of my Rapido barrel), I noticed that if I grabbed the flywheel and gave it a pull/push at 90degrees to the crankshaft axis I could feel a little play. With the crankshaft out there didn't seem any bad signs of wear on the inner and the bearing is the FAG NU2205E, so good quality.
Is a little bit of play normal when cold? Does it get tighter as the engine warms up? (I've read thats why you need a "C3" spec bearing for the drive side)
Looking forward to any info you lot can come up with!

[bristolmod]

Generally this is an area where there should be no apparent play detectable- if you can detect play then there is wear, which means a replacement I'm afraid.

I had an LI125S a couple of years ago which had a "knock" from the crank area- all I could detect was the smallest amount of play on the flywheel, so I changed the bearings.

Result- no play and the knock gone

I'm assuming the actual flywheel is nice and tight on the crank taper?

Sorry

Chris

[nelson pk]

Generally this is an area where there should be no apparent play detectable- if you can detect play then there is wear, which means a replacement I'm afraid.

I had an LI125S a couple of years ago which had a "knock" from the crank area- all I could detect was the smallest amount of play on the flywheel, so I changed the bearings.

Result- no play and the knock gone

I'm assuming the actual flywheel is nice and tight on the crank taper?

Sorry

Chris

I have to disagree.........a little!
There will be a very small amount of play even in a fairly new bearing and some new as there is a certain amont of tolerance with these bearings and as you state the C3 number on the bearing tells you that tolerance which allows for expansion under load/heat etc.
If it is what i would call "sloppy" with a pronounced knock when you try to move the flywheel up and down or side to side then i would say replace.

[warts]

I think being able to "feel" free play means there's probably too much, but then its likely that you will have much more sensitive fingers than me.
Sure any sort of sliding fit will have some free play, but a few thou would be difficult to feel.
AS you can see, for a 50mm bore C3 <0.004max. Does this feel about what you have? Could you put a dti on it?
http://www.skf.com/files/150828.pdf

[Minority]

Thanks for the replys,

Flywheel seemed tight on the taper so I don't think it was that.
And as there is no "C3" designation on the bearing I presume that it's just a "normal" clearance bearing.
Thanks for the link to the SKF file Warts, it makes interesting reading. As I read it, the normal radial clearance for a 25mm diameter (thats what the NU2205E is) is between .0008 & .0018.
Think I'm going to replace it for peace of mind (and then curse when I find the new one feels exactly the same )

[coaster]

Flywheel seemed tight on the taper so I don't think it was that.

It's worth checking the rivets securing the boss to the flywheel are tight. I recently saw one that had been welded that was loose, weld cracked and rivets had worked loose