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Aprilia mx125 crankshaft bearing question

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Timo 30
L Plate Warrior



Joined: 11 Jan 2014
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PostPosted: 18:30 - 11 Jan 2014    Post subject: Aprilia mx125 crankshaft bearing question Reply with quote
Took the bike out today and it seized up
I've stripped the barrel off and the piston and rings are fine.
If I stand on the kick start with out the barrel on the
Piston struggle to move up and down

So the question is is the bottom end bearings gone ?

Any help would be great thanks
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merky69
Borekit Bruiser



Joined: 02 May 2013
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PostPosted: 18:54 - 11 Jan 2014    Post subject: Re: Aprilia mx125 crankshaft bearing question Reply with quote
Timo 30 wrote:
Took the bike out today and it seized up
I've stripped the barrel off and the piston and rings are fine.
If I stand on the kick start with out the barrel on the
Piston struggle to move up and down

So the question is is the bottom end bearings gone ?

Any help would be great thanks


Sounds like main bearings have seized if barrel and rings are fine , usually still get travel marks from a seize on the barrel , id advice new piston and rings just to be safe anyway whilst the mains are done .
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Timo 30
L Plate Warrior



Joined: 11 Jan 2014
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PostPosted: 19:03 - 11 Jan 2014    Post subject: Reply with quote
There is a little scrape marking on the inside

Are the main bearings easy to replace ? Only ever replace bearings on a car so bike is new to me
Cheers for the help
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merky69
Borekit Bruiser



Joined: 02 May 2013
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PostPosted: 20:29 - 11 Jan 2014    Post subject: Reply with quote
Timo 30 wrote:
There is a little scrape marking on the inside

Are the main bearings easy to replace ? Only ever replace bearings on a car so bike is new to me
Cheers for the help


you will need to warm the case up using a hot air gun so the haynes manual states ( i use gas)and a flywheel puller.

pretty simply just split the case the crank will remain in rh side of the case you will need to remove flywheel with a puller and remove stator windings, then heat up behind the bearing and you should be able to pop the crank out, (dont hit the crank thread with a hammer you will damage it) use something to go over like 13mm deep socket for a bodge lol. after tht u need to get the bearing off the crank, slide hammer works well for me. (reverse to assemble but heat the bearing up before puttin on crank. then let cool and heat case then slide in crank and bearing.

LH side case just heat back of bearing and tap out using a suitable size socket, heat again then pop in new bearing

hope this helps

as for the mark on the barrel can you feel it with your finger nail if so it ideally needs a replate.
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Timo 30
L Plate Warrior



Joined: 11 Jan 2014
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PostPosted: 13:26 - 12 Jan 2014    Post subject: Reply with quote
Cheers for the help also noticed putting new bearings in a cold bucket of ice will help as well as heating area they will go in.

I'm taking the whole engine out to work on it.

Is there a certain way the rear engine to frame bolts come out ?

The nut on one side comes off easy but the other bolt on the left hand side just spins. It has a small hole in side in the nut. Is this a form of lock nut ?
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merky69
Borekit Bruiser



Joined: 02 May 2013
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PostPosted: 17:01 - 12 Jan 2014    Post subject: Reply with quote
hi yes the swing arm bolt will only unscrew so far once u are at its point where it wont unscrew any more u jus need to pull it out. (grip it with something and give a twisting pull motion)

you dont need to touch the locking nut , or anything that side!

also avoid puttin your bearings in any kind of water it isnt good for them at all. water leaks in the crankcase is a common cause of main bearing failure so i would just avoid using water totally. just put them in the fridge or freezer if this is required , but i have never needed to.
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