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Main bearings reassembly


markparrish
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Hi, I have just fitted new mains to my 2007 rev3. They are the "new" type with rubber seals both sides (the ones I removed had metal seals). I got them in ok by putting them in the freezer for a while then heating the cases with a hot air gun and gently tapping with a rubber mallet. My question is - will I damage the seals or ruin the internal grease by heating them when I reassemble the case - or is there another way? 

Thanks, Mark

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This is taken from the 2016 Evo engine rebuild manual.

 

CLOSING THE ENGINE CASING
Insert two centring bushes A and replace the gasket with a new one. Once the seal is replaced with a new one, heat the main bearing and the area around it on the right casing. Continue heating until the casing enters the motor shaft with minimal hindrance. Before starting the heating process it is recommended to grease the oil seal found on the outer side of the half-casing.

ATTENTION!
Be careful not to deteriorate the oil seal while heating the bearing. Press the right half-casing towards the left half, ensuring that the shafts, bolts and pins on the casings are inserted into their respective housing and the half-casing is positioned correctly. To make it easier to draw the two half-casings closer together and line them up, it is possible to use two screws, or more, on opposite sides and tighten them gradually. If the casings do not remain in their correct position, do not tighten further but loosen the screws and set the casings back into their correct position.Ensure that the two casings fit perfectly then mount and tighten the recessed hexagonal head screws (M6x50), whose tightening torque must be 10Nm. It is recommended to tighten the screws in a cross-wise pattern. Then carefully cut the excess parts of the seal in the cylinder area and intake pipe. Give a few blows to the end-parts of the motor shaft with a rubber hammer in direction of the axes so as to release any residual stress on the casings caused by the heating 
process.

Edited by rcgods
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Sealed bearings can be re greased as they often don't come with much in anyway. Grease condition can be easily checked by carefully picking off the rubber seal the using the point of a Stanley knife blade. Ball Race can then be repacked with your desired product. Seal just pushes back into place when finished. Don't overpack ball race though. Particularly useful for wheel bearings, which don't seem to last five minutes these days. Always buy the best quality bearings you can, as there is a lot of poor quality stuff out there.   

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Have the crankshaft cold and the cases and bearings warm. Pull the crankshaft into the bearings by using tubular spacers and washers and the pinion and flywheel nuts. Do not do anything that transmits assembly force through the ball bearings.

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  • 1 month later...

Just a quick update... I have finally gotten round to refitting the engine after the rebuild - I've been very busy unfortunately so it's been on the bench for ages :-(

It started up after a couple of kicks (which was reassuring as I had forgotten where a lot of wires went and had to use a bit of initiative) and sounds so much better now! I can now hear the clutch whirring instead of the grinding noise from the bearings! For the record I improvised some spacers from sockets and large washers and used the crankshaft nuts to gently squeeze the cases together and bearings into position, taking care that there was always plenty of thread engaged when applying the pressure. Once assembled a few taps with a nylon mallet to relieve any stresses and everything seemed to turn very nicely. I also took care when reassembling the clutch to have all the rounded edges facing outwards and I gave the basket edges a smooth/polish before reassembly as I could see where the plates were bedding in and had noticed a bit of grabbing when selecting gear from neutral when cold - that seems better too.

I just need to get out for a practice now - having stopped for a while due to broken collarbone and ribs! - hope I haven't lost my nerve!

thanks for all the help (on many of these pages), Cheers, Mark

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