Author Topic: How much is too much? Crank bearing play  (Read 1340 times)

Offline Resto-Rob

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How much is too much? Crank bearing play
« on: 27.06. 2014 18:02 »
Hey guys...

Yet another question....
So im still tracking down the oil in the mag problem, and it seems to have come down to a leaking oil pump leaving too much oil in the timing cover....
So i stripped off the oil pump, made a new gasket, cleaned everything up and re fitted it....
This is when i noticed there is quite a bit of play in the drive end of the crank.... Maybe the bush is worn and the up and down play from the crank has put pressure on the oil pump causing it to leak???
So my question is, how much up and down play is too much?  *conf*
When life throws you a curve..... lean into it!!
1953 BSA A10 Plunger
1927 BSA S27
Austria

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Re: How much is too much?
« Reply #1 on: 27.06. 2014 21:22 »
G'dar Rob.
In a perfect world, if you can feel movement its too much. If you can set up a dial indicator to the case securely, measure the up & down movement. 2 thou" OK, 5 thou" too much.
There is always a bit of oil in the cover when you take it off. Always a good idea to check the pump nuts when the cover is off. Mine usually need a tad. It still shouldn't get into the mag.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
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Offline a10gf

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Re: How much is too much?
« Reply #2 on: 27.06. 2014 21:37 »
Quote
if you can feel movement its too much
Well said.

And from there it could (will) escalate = gradual loss of oil pressure trough the crank to the big ends. So it may soon be time to prepare for some main bearing work.

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Offline Resto-Rob

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Re: How much is too much?
« Reply #3 on: 27.06. 2014 22:56 »
There was quite a bit of oil when i removed the timing cover which made me suspect the oil pump...
Damn! I was hoping to actually ride this season, that is why i bought the bike :(
Looks like a complete strip down and hope i dont find any other problems along the way...
When life throws you a curve..... lean into it!!
1953 BSA A10 Plunger
1927 BSA S27
Austria

Offline wilko

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Re: How much is too much?
« Reply #4 on: 28.06. 2014 01:23 »
It's wetsumped. Drain it and ride it.

Offline Resto-Rob

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Re: How much is too much?
« Reply #5 on: 28.06. 2014 07:47 »
That is always an option....
Strangely there was very little oil in the actual sump, only in the timing cover.  The whole reason behind this partial strip down is it stopped running and wouldnt start again.  If i get it going now, ride it and blow the engine it doesnt really help, not to mention the potential long walk home...
When life throws you a curve..... lean into it!!
1953 BSA A10 Plunger
1927 BSA S27
Austria

Offline charles whitfield

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Re: How much is too much? Crank bearing play
« Reply #6 on: 28.06. 2014 14:37 »
And Big Bill calling round

Offline Resto-Rob

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Re: How much is too much? Crank bearing play
« Reply #7 on: 28.06. 2014 18:24 »
Yeah, i hate that guy....
When life throws you a curve..... lean into it!!
1953 BSA A10 Plunger
1927 BSA S27
Austria

Offline Resto-Rob

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Re: How much is too much? Crank bearing play
« Reply #8 on: 29.06. 2014 11:16 »
So.... The limit should be .002, well i got to .007 before cracking up laughing at what lays ahead....
Guess what im doing this afternoon? :)
When life throws you a curve..... lean into it!!
1953 BSA A10 Plunger
1927 BSA S27
Austria

Offline a10gf

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Re: How much is too much? Crank bearing play
« Reply #9 on: 29.06. 2014 13:21 »
Quote
Guess what im doing this afternoon?
2 alternatives ?

1. Sit down, drink beer, shout at the family and neighbors, cry.
2. Strip the engine, check everything, find a good engineering company to fit a new timing side bearing.

 *smile*

If most  things look ok with the engine, it does not need to be an expensive job. & remember to check\clean the sludge traps, and do good work with the crank end float shimming. Good luck

ps, maybe MG in Austria can be of help.

A10 GF '53 My A10 website
"Success only gets you a ticket to a much more difficult task"

Offline Resto-Rob

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Re: How much is too much? Crank bearing play
« Reply #10 on: 29.06. 2014 16:00 »
As tempting as the first option was i went with the second one :)
As soon as i removed the head i saw a good 3mm of fresh oil sitting on the pistons....
Then i removed the barrel to find the lifters are completely stuffed and naturally the cams are the same way :(
Oh dear i said to myself ;)
So i checked that the valves are seating ok and they are however there is oil inside the intake side...
Te exhaust side is dry.
Could the oil be coming is past the gasket from the pushrods??
I dont think the whole amount came from the head, and the bore and piston clearance is mint....
I will keep on going deeper and wait for Mr Bill to arrive.....
When life throws you a curve..... lean into it!!
1953 BSA A10 Plunger
1927 BSA S27
Austria

Online chaterlea25

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Re: How much is too much? Crank bearing play
« Reply #11 on: 29.06. 2014 16:14 »
Hi Rob,
The cam wear will be a result of the worn main bearing losing oil pressure and not diverting oil to the cam trough when the PRV opens
Usually the shrapnel from the cam/followers wrecks the pistons and bore so count yourself luck there
The oil in the bores could be from the inlet valve guides as there is oil in the inlet ports
sometimes the guides are loose in the head more often on the exhaust side though or just wear between valve and guide
Another possible cause is that the wrong feed bolt was used on the rocker feed, as the bolts from single cylinder models have different size restrictor holes or just a big hole for the rocker drain pipe
These all look the same externally except for the different drillings
I can only recommend that you fit a new oilpump during the overhaul and dont forget the anti wet sump ball valve in the RH crankcase

HTH
John

1961 Super Rocket
1963 RGS (ongoing)

Offline charles whitfield

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Re: How much is too much? Crank bearing play
« Reply #12 on: 29.06. 2014 17:18 »
Don't worry, Big bill is here at the moment
Have oily fun!

Offline Resto-Rob

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Re: How much is too much? Crank bearing play
« Reply #13 on: 29.06. 2014 17:26 »
Great! Keep him busy at your place...
He will love to hear that my drive side conrod is also bent and the big end shot....
On the bright side, this bike will be like new once i have finshed with it :)
When life throws you a curve..... lean into it!!
1953 BSA A10 Plunger
1927 BSA S27
Austria

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Re: How much is too much? Crank bearing play
« Reply #14 on: 29.06. 2014 21:00 »
Bugga,bugga,bugga. At least you didn't spend too much time trying to start it only to find it go bang in a big way.
I always account for a engine rebuild on any new acquisition.
Good luck Rob and don't cut any corners.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7