Author Topic: Crankshaft end play  (Read 1380 times)

Offline pete3000

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Crankshaft end play
« on: 24.07. 2012 15:07 »
Hi everyone,

When timing my BSA, I had to take off the timing plate and notice that I had about 0.020" end float on the crankshaft. That's really to big ! considering the haynes
manual requiring 0.003".
I really don't undestand how could this happen. The engine has 1000 miles, and had no end float when putting back in the frame. I remove the sump plate to see if
I could find any broken shims but unfortunuatly haven't seen any. The cush nut is well tight.
I don't know if I have to split off the cases for more investigations. The engine runs well, no strange noises...
Main bearing damaged ?
 

Online RichardL

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Re: Crankshaft end play
« Reply #1 on: 24.07. 2012 16:03 »
Curious how you came by the 0.020" measurement. I haven't tried it with the engine in the bike, but can imagine some ways. Leaving my imaginings out of it, how did you do it?

Richard L.
Plan on signing up for the world-wide 2020 DISTINGUISHED GENTLEMAN'S RIDEon September 27, 2020. This year it's a solo or pillion ride in dapper attire. Watch website at https://www.gentlemansride.com for details.


Offline pete3000

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Re: Crankshaft end play
« Reply #2 on: 24.07. 2012 16:20 »
Hi Richard,

I took off the primary case. Took a dial gauge well fixed to the other hand of the crankshaft (timing side) and mesure the end float by pushing the crankshaft.
I know, it's not a sophisticate way to mesure the end float but gave me an approximative measure.
I notice about 0.020 maybe 0.025 but I know that my measures aren't very exact, just say to me that there is a problem.

Online bsa-bill

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Re: Crankshaft end play
« Reply #3 on: 24.07. 2012 19:32 »
Did you place the shims between the bearing and the crank, reason I ask is this has sort of come up before, reason being the shims had been put between the  bearing inner and the crankcase, this bit rotates so shims rotate and wear and break up, bearing inner should be stationary in relation to the crank, ie it should rotate with the crank and shims the same so nothing in that bit should wear.
Sometimes the bearing is not quite a tight enough fit onto the crank and the crank rotates within it and again wears the shims

Not too helpful I'm afraid as not much can be seen with the crankcases bolted together
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline pete3000

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Re: Crankshaft end play
« Reply #4 on: 24.07. 2012 20:30 »
Thanks Bill for your reply. Shims between bearing and crankshaft.
I have read on the forum several posts about the end float, and what I notice is that it is not
good to have more then 0.003' end float.
I'm quite worry about that big end float, I think I would have to split off the cases to find out what happen. *conf*
 

Offline muskrat

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Re: Crankshaft end play
« Reply #5 on: 24.07. 2012 20:55 »
 G'day Pete,
                that's way too much. Possibly the bush might not have been all the way home when assembled for shim measurement. Must be rectified, motor out, cases split. Take an accurate measurement now so you know how much to shim. Once opened up have a good look at the thrust face of the bush for excessive wear. I don't have a new one but someone here might have one to measure the thickness of the thrust face for you to check yours.
 Cheers
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Australia
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Offline BSA_54A10

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Re: Crankshaft end play
« Reply #6 on: 25.07. 2012 06:49 »
And from left field.
Where did you anchor the dial gauge to ?
If it was not firmly attached to the engine you may have been measuring flex in the frame.
Bike Beesa
Trevor

Offline muskrat

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Re: Crankshaft end play
« Reply #7 on: 25.07. 2012 08:28 »
 Ha, good one Trevor. That would be a relief, never had to shim more than 15thou myself.
Cheers
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Offline pete3000

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Re: Crankshaft end play
« Reply #8 on: 25.07. 2012 08:52 »
You are probably right about the fact that the bush might not have been all the way home when fitted, but it was the case as I remember. 
The gauge was firmly attached to the engine, and unfortunuatly I don't think I have measure the flex in the frame. If it had been that, it would have been good news for me !
When I push the crankshaft with my hand, I can see it moving very well.  I have measure again the end float and it's more 0.015' - 0.018', a bit less that I announce, but still
not good.
It's a lot of work to split off the cases, remove the engine, take off the pistons....
Before I start the job, what can happen with too much end float ?? I 'm saying this because, I don't want when I will reassemble the engine, and go for a ride, that the end
float will come again. I didn't have any when I rebuilt the engine, an I'm curious to know what cause this ?? Bearing wear ? Bush wear ? but why the bush will wear ?
I have new SRM pump and the oil flow was very good.