My engine sounds like a sea shell.

[msmola2002]

Just helped a guy rebuild the engine from my old KX. Had bad crank bearings. Reassembled using an oven and freezer. Pressed the seals in with an appropriately sized socket then placed in oven, crank/bearings in freeze in freezer. Bearings plop into case. Case back in oven. Drop frozen crank into tranny side of case, with a feeler gauge of size I don't recall to keep crank clear of case. let it cool. then freezer. Then, heated a cheap socket with a blowtorch resting on centre of the other crank case's bearing til hot, and then popped onto frozen tranny/crank half.

Piece of piss.

[cnrcpla]

I go away for a couple weeks and you get an ocean in your YZ stu?  Lets see some pics once you get it all opened up. 

[Stusmoke]

I can't wait to see how bfed it is internally. I really don't think this bikes been taken care of well. The carby was fubar the front forks were fubar. When I persuade my folks to get the tools we'll see how I go. This will be the first time I ever rebuild an engine too. Fingers crossed right? I'm researching up at the moment.

Just helped a guy rebuild the engine from my old KX. Had bad crank bearings. Reassembled using an oven and freezer. Pressed the seals in with an appropriately sized socket then placed in oven, crank/bearings in freeze in freezer. Bearings plop into case. Case back in oven. Drop frozen crank into tranny side of case, with a feeler gauge of size I don't recall to keep crank clear of case. let it cool. then freezer. Then, heated a cheap socket with a blowtorch resting on centre of the other crank case's bearing til hot, and then popped onto frozen tranny/crank half.

Piece of piss.

Would I be correct in saying that the theory behind that is the metal contracting and expanding with the different heat? couldn't being heated to both those extremes weaken it?

[msmola2002]

Yes.

And no.

To anneal the steel in the bearings you would be up at least 600c, process annealing begins at 265ish. You don't crank the oven that hot. About 150c.

The bigger issue is not frying the seals, but they will be ok at 150.

[eprovenzano]

Stu I rebuilt my son's Honda 400ex. I had helped a friend replace the crank on his KX125, so I did have some 1st hand knowledge, but it's not as hard as it may seem.  My one piece of advice, as you remove things, nuts washers, gears etc., put a plastic wire tie on them to keep them together.  Not only does it keep the proper components together, it keeps them in the proper order.  Take your time, with some patience, (and a good manual) you can rebuild her.  In the end, you will know her inside and out, plus you will have the satisfaction of knowing you did it.

[Stusmoke]

Yes.

And no.

To anneal the steel in the bearings you would be up at least 600c, process annealing begins at 265ish. You don't crank the oven that hot. About 150c.

The bigger issue is not frying the seals, but they will be ok at 150.

Makes sense. Cheers for that.

Stu I rebuilt my son's Honda 400ex. I had helped a friend replace the crank on his KX125, so I did have some 1st hand knowledge, but it's not as hard as it may seem.  My one piece of advice, as you remove things, nuts washers, gears etc., put a plastic wire tie on them to keep them together.  Not only does it keep the proper components together, it keeps them in the proper order.  Take your time, with some patience, (and a good manual) you can rebuild her.  In the end, you will know her inside and out, plus you will have the satisfaction of knowing you did it.

Thanks Eric. I've been watching dozens of videos on it and it doesn't look all that intimidating. Better than a top end on a fooper right? I've got a good manual so thats a big hand and I have a system of writing out the part on a note pad, tearing the page off and putting all related bearings, seals, orings, nuts, washers etc on that piece of paper. I will definitely cable tie the gears and anything else that comes apart together. Thanks mate