E: Engine Main bearings

Vincent Brake

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Heat the inner roller race with an electric heat gun (like a hair dryer) with the bearing hanging on a punch held in a vice, then using some long nose pliers slip the bearing over the mainshaft and it should slip fully home very easily. You can use this method to remove bearings too although it will take some heating as the shaft will soak up some of the heat........saves any mechanical damage to the bearing.

And if not get the oxigen torch out.
 

tatty500

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If you've just spent a million quid buying new mains, then it is important to treat them properly.


SKF and RHP instruct us not to heat a bearing to more tan 120C "or the bearing hardness will be affected"..... and"a naked flame should never be applied to bearing components".

When using an oil bath even it should be indirectly heated in a water bath.

Tatty
 

SteveO

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Yes Bill, new mainshafts. I've now driven the bearings on (not brutally!), I used an old Moto Guzzi fork leg that is a good fit on the bearing inner and over the shafts. Now for the next problem. In the photo attached, you can see a bright spot on the housing (where a liner has been fitted because the housing was damaged) and on the retaining screws for the bearing plates. This is where the big end pin itself, not the nut, is making contact. So what is the solution? A shim on the mainshaft behind the bearing seems most logical, however this may put the crank too far over (as Stu suggested, the oil pump worm is already up against the bearing, not the step in the shaft and this is without the timing side being shimmed). Haven't got as far as putting the cases together yet to check centrality (!) of the rods. Did have to source an oil scroll for the alloy spacer as my engine didn't have one!
 

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Martyn Goodwin

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Yes Bill, new mainshafts. I've now driven the bearings on (not brutally!), I used an old Moto Guzzi fork leg that is a good fit on the bearing inner and over the shafts. Now for the next problem. In the photo attached, you can see a bright spot on the housing (where a liner has been fitted because the housing was damaged) and on the retaining screws for the bearing plates. This is where the big end pin itself, not the nut, is making contact. So what is the solution? A shim on the mainshaft behind the bearing seems most logical, however this may put the crank too far over (as Stu suggested, the oil pump worm is already up against the bearing, not the step in the shaft and this is without the timing side being shimmed). Haven't got as far as putting the cases together yet to check centrality (!) of the rods. Did have to source an oil scroll for the alloy spacer as my engine didn't have one!

Your upcoming problem is REMOVAL of the new bearing from the mainshaft on the driving side so you can centralize the rods.

As I said earlier before you do that on the Drive side you must first determine what if any thickness shim you need between the bearing inner and the flywheel in order to centralise the conrod. See OVR edition 18 - in the OVR Archives for details on exactly how to do this - you will need the inner of an old main bearing to make a measurement spacer - that edition is in the OVR archives here https://ovr270.wixsite.com/ozvincentreview . All shims MUST be placed between the flywheel face and the bearing

Martyn
 

Bill Thomas

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The problem might be getting the bearing off to put a shim behind ?, Hope not.
If the mainshaft was too big, It needed making smaller.
Some people use a chisel, Just to get it away from the wheel, I don't like that.
With the old brass cage you could get the puller to rest on the inner of the rollers, And pull the bearing off.

Wish you had an arrow to show the mark, Like Bruce does !, I can't do that !.
Do you mean the mark high up ?.
Also looks like something is rubbing on the screws ?, I hate that fitting.
As you say it looks like it will need a shim behind the drive side inner bearing
But you really need to see if the conrods are in the middle.
I wonder if you have a Big Pin Bigend, That sticks out more than the standard one,
I had this years ago, When I laid the Bike over to the left the Pin hit the C/C wall, Felt like the end of the world,
I was Racing at the time !!. People said I was a bit Slow, A, Richard !!.
When George Brown fitted me a Big Pin, Many years ago, He ground off both the bits of Pin that was sticking out, That's what I would do next time, But you have to do little at a time, With an angel grinder, So as not to over heat the Pin !!
Not sure you understand what Stu was saying, I think Stu ment , The Worm must be out wider than the step,
So that every thing is nipped up, See what other people say, It's a bit tricky.
 

Bill Thomas

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Have you remembered to put the small Oil scroll on the shaft, The bit that fits inside that big alloy disc
Between the 2 drive side bearings ?.
Sorry I can see it now.
Can you give us a photo of the crank pin and nuts.
 

SteveO

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Bill, yes I thought the oil scroll was going to fix the problem. As I said above, my engine actually lacked this part. But it's made no difference. I appreciate that I need to centralise the rods, but there seemed little point in moving on to this before I got the crank turning without banging into something! I have had a mail conversation with Davidd on here and he suggests a cheap bearing seperator, ground to fit, to start the bearing off the shaft, so that is my next purchase. My thinking now is that since I probably need to shim the bearing to get clearance anyway, I am going to have to go with whatever that takes and hope the rods line up. I have to get the drive side free turning, as that is the side that is tightened up against pulling the crank over, not the timing side. I don't like the fitting on the main much myself, it is horrible, but I'm stuck with it unless I either scrap the case for a modern replacement or undertake major machining work that I can't do myself. I do have some F1 contacts and an engineer friend who told me that TZ750 Yamahas were raced in the Island with the bearings glued in with Loctite. I dont intend to use the bike THAT hard! In the meantime here are some photos of the crank. I am starting to wonder where this build is going as every time I fix one problem another crops up; it's beginning to get me down if the truth be told...
 

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Bill Thomas

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Chin Up Steve, Just think how good you will feel if you can sort it all out.
If it was easy every body would be doing it.
As a rule the raised bit on the flywheel is about 30 thou.
If it's not worn down because of inner bearing spinning on the shaft before.
As I thought you have a big crank pin and nuts, I don't know why they make them like that,
Mine stuck out even more than yours !!
Have a read up on what Martyn says.
If its just the pin that is touching, As I said you can grind a bit off, Which is why I said you should find where the conrods are, If in the middle ?.
And looking forward, Check on where the oil hole is in the barrel liner, It wants to be below the bottom of the lower oil ring
 

SteveO

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Right, I've read the OVR archive article. I have the perfect start for a bearing spacer - the old bearings! Job 1 is get the new bearing off the drive side and start again. I'll check where the conrods are. If they do need shimming and I'm pretty sure that they will, hopefully this will kill two birds with one stone!
 
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