Author Topic: Main bearing oil ways.  (Read 1554 times)

Offline Backmarker

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Main bearing oil ways.
« on: 16.06. 2012 21:16 »
Hi
Im new to this forum and hope someone can help me with this.
I done the big end (timing side) got the crank. reground new shells (good as new hopefully)but on looking at timing side bush oil ways they don't line up with the oil ways on the crankshaft is this the correct.
Thanks.

Online beezermacc

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Re: Main bearing oil ways.
« Reply #1 on: 16.06. 2012 22:19 »
The timing side bush has a groove around the outside so oil is pressurised into the groove from the pump then the oil passes through the holes in the timing side bush into the groove in the crankshaft journal. You will notice a hole in the groove in the crank journal which conducts oil to the big end journals. Hope that's clear. If your engine is dismantled you can identify the four holes which mate with the back of the oil pump and squirt oil down them. You will see oil dribbling through the timing side bush holes. This shows that oil pressure is reaching the crankshaft. Some timing side bushes are one-piece lead/bronze, some are two-piece bronze in steel - make sure the oil holes are continuous through the bronze and steel if you have this two piece bush.
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Offline a10gf

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Re: Main bearing oil ways.
« Reply #2 on: 16.06. 2012 23:01 »
Welcome to the forum, pictures + story of bike always appreciated.

If I do get this right, with the parts you've got, the oil holes in the bush do not line up with the crankshaft groove?
Such an offset could be a very destructive trap!

Out of interest did a check (with my worn bush\crank), lines up pretty well here, and I think this is the way it should be. Would tend to think + or - a 1\2 mm from centre should not matter much, but much more that that and oil could get restricted on it's way into the crankshaft oilways.

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Offline chaterlea25

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Re: Main bearing oil ways.
« Reply #3 on: 18.06. 2012 15:00 »
Hi Backmarker,
Welcome to the Forum,
MAKE SURE TO CLEAN OUT THE CRANKSHAFT SLUDGE TRAP BEFORE YOU REBUILD THE ENGINE  *eek* *eek*
Check for threads on the subject on the forum
HTH
John O R
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Offline Backmarker

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Re: Main bearing oil ways.
« Reply #4 on: 19.06. 2012 20:54 »
Trying to up load a photo of the main bearing which shows the oil passage runs very close to the main bearing oil holes .If as you say they should line up this more than probibly caused the big end to fail.

Offline Backmarker

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Re: Main bearing oil ways.
« Reply #5 on: 20.06. 2012 20:30 »
Managed to get a photo up loaded (with a little help from my sun).You can see the dark line from the journal oilway only just reaches the main bearing oil holes .The oil must have bean restricted quite a bit.
ps. The bearing is in reasonable condition the picture makes it look quite scored.

Offline a10gf

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Re: Main bearing oil ways.
« Reply #6 on: 20.06. 2012 20:38 »
Wow, important find! From my picture above, you can see the non-wear area on the bush is right on the oil hole drillings. Either you've got the wrong bush, or the wrong crankshaft (....or both!). Others here may come up with an explanation.

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Online muskrat

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Re: Main bearing oil ways.
« Reply #7 on: 20.06. 2012 22:54 »
 G'day Backmarker,
                          either there's a bad batch of bushes out there or as e said the wrong one. As far as I know all the A7/10 shafts are the same on the main shaft. The A65's are differant diameter but same length. Did you fit the new bush? Is there any thing dodgy on the drive side?
 A quick fix would be to elongate the holes with a dremmel.
Cheers
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Online Brian

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Re: Main bearing oil ways.
« Reply #8 on: 20.06. 2012 23:49 »
You need to check out everthing but I think there is fair chance the problem lies with the bush.

When the bush is removed from the case you will see it has a groove in the back of it where the holes are drilled through, the holes are drilled at an angle so they line up correctly with the crank, I think yours have been drilled straight from the groove instead at the angle.

You are sort of lucky, this could have caused a big blow up.

Offline Backmarker

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Re: Main bearing oil ways.
« Reply #9 on: 22.06. 2012 19:45 »
I have done just over 2000 miles since i got the bike i suppose i have been very fortunate it has lasted so long .The bush was fitted by a previous owner when, i dont know.Would elongating the holes be an safe option ?

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Re: Main bearing oil ways.
« Reply #10 on: 22.06. 2012 21:38 »
 G'day Backmarker,
                          won't hurt at all (better than it is) as long as you clean it all out (prv off).
Cheers
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Online KiwiGF

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Re: Main bearing oil ways.
« Reply #11 on: 23.06. 2012 00:09 »
Rather unlikely but maybe someone made a special bush with thicker than normal flange to take up crankshaft end float? But did not take into account the oil feed hole position?

Either way as per above it needs fixing! (another thing on my checklist albeit an engineer who knows his stuff is making an special bush to fit a worn housing on my cases)
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Offline Backmarker

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Re: Main bearing oil ways.
« Reply #12 on: 24.06. 2012 15:02 »
Thanks for all the help on this matter.I have checked to see if the back of the bush aligns it appears to be ok.