Crank case transplant. Help Please!

I have a bad crack in my wr 450 crank case and am about to order a new one and transfer everything over to the new one. Any idea if bearings are transferable, or should you never reuse them,should every one be replaced? Would you rather press them in or sweat them? Anyone done this before? Any help would be great! I've seen great videos but I would just like a few more tips if i could get em. Thanks! :smashpc:

well, chances are, you're better off just re-doing the entire bottom end if you're going to be getting a new case..

so, i'd get new bearings if it were me.

Rarely can the bearings be pulled (or pressed) out without damage. Replace them.

Edited by William1

For doing the case swap you'll need all new bearings, seals, locktite red, locktite blue and a tube of Yamabond (or threebond 1194) to seal the case halves. A couple tools you'll definitely need include a flywheel puller, some good quality Torx sockets and some Hex sockets, a good quality torque wrench, and a oven that you won't get into trouble for baking engine parts in :thumbsup:, also you'll need access to a press that you can remove the bearings from the crank. Also be prepared to have some freezer room available to freeze some of the parts.

To install the bearings, the method I found to be least detremental to the bearings health is applying heat to the case halves (about 200 deg C) for about 20 mins, and freezing the bearings/crank over night in the freezer. If you're using heat/cold properly, then all the bearings will be a drop fit without the need for any special tools to get the job done. I've heard that some ppl like putting a smear of locktite red/blue on the outter race of the bearings (I didn't do it), to aid in A: aiding in sliding bearing into place and, B: to provide an extra lock to stop the bearing from possibly spinning within the case halve, but our engines have anti rotation tabs so I felt it wasn't worth the risk. Just make sure that if you apply the locktite do it sparingly to stop the possibility of getting anything on the rollers.. If anything gets on those rollers, the bearing is done. All hardware inside the case gets locktite red and torqued to specs, everything outside the case gets locktite blue when it's called for.

After the bearings are installed with the anti rotation tabs torqued, put the cases back into the oven (again for 20 mins) and heat before you install the frozen crank. You'll be surprised how easily that crank installs into place.:smashpc: Then, install the transmission, apply the threebond goop sparenly to the case half, and slide the already heated other half into place. Wait for everything to cool, then install the outter seals.

Be prepared to spend some time, and be patient. If it doesn't seem like it wants to go, don't force it and investigate what's happenning. Also, spend the money now and get OE seals and bearings. I've had nothing but problems with any aftermarket seals.... they ALL required replacing after... (I used OE bearings during my build)... so save yourself some time and cash and do it right from the beginning.

Lastly, the Neutral position switch... ah... my arch nemisis.... find someone with an impact driver to remove those stubborn screws. Don't even attempt to just use a screwdriver on them... they'll strip faster than a teen on prom night. When you get them out, find a suitable replacement of a hex screw and solve your headaches for good.

If you've got any other questions, don't be affraid of sending a pm. The only stupid question is the one that wasn't asked.

Edited by rs25

Wow, very good stuff here my friend, very helpful , can't thank you enough. Few questions, so i'll need a press to take the bearings out of the crank, not an actual crank puller? And then I'l be able to just sweat the crank back into the new case, i wont need that yamaha tool?

Nope, the only really special tool I needed was just that flywheel puller. You could use the case splitter/crank puller tool to supplement using a press, but I didnt because I have access to a press, dry ice, and industrial ovens. Oh, I just remembered, pick up some fairly thin aluminum sheet, so you can use the stuff to wedge between adjacent teeth of various gears to remove/install any retaining nuts. It's perfectly safe (because the allu won't damage steel), cheap and works excellent. Also, you'll need some way to hold your clutch basket too.

The special tool yamaha shows in the manual can be substituted for sweating everything into place.

Ive never used the oven method but How long can a seal last in a oven without being damaged?? 20 minutes??

I heated the cases w/o seals installed. Basicly the first thing you'd be doing is installing the bearings.. so, only install the bearing.

After the two case halves are joined, then I install all the seals.

Thanks and Great info for most bikes ....but the reason I asked about how hot the seals can get is because on my bike the seals must be installed first ( from the inside of the case) then the bearing is installed next

I did leave the clutch push rod seal installed in the cases when I was rebuilding, and it never melted.

You don't need to get the cases or components so hot you could cook off them, you just need a evenly distributed, obvious tempurature change between the two parts. 200°F is actually right around your average engine operating tempuratures... I think the WR's like to run around 190-200°F anyways with the danger area around 240-250°F.. and I'd assume most other bikes run aprox the same temps. Another reason for freezing the components is you don't have to apply too much heat to the other part.. Heck, you could probably get away with only heating to 150°F if your oven goes that low, because you'd still be applying almost 200 degrees differential temp. I used 300F because that was the lowest setting to turn on the oven I was using and it worked great.

Edited by rs25


Are you sure about those temps?

Plain water not under pressure boils at 100C or 212F.



200C= 392F


If I remeber correctly the coolant I have in my engine boils at about 121C or 250F which to me would mean the engine is overheated if it boils over.

190-200 C or 374-392 F which you referenced seems like a really hot operating temperature to me.

Not trying to be a jackass but I wouldn't want someone accidently melting seals by heating them too much. :lol:

hey, that's no problem ur2silly at all, you are right. I'll ammend my post.. I was thinking 200-220F as operating, and 240F as warning.

I know the seal which was installed on my case wasn't affected by the oven temp. Other manufacturers, well.. I can't say.

One thing you can try is do a "dry run" and see how the factory seals react with the temp. Obviously you removed a seal, which is now scrap... well.. turn on your oven to 200 F, put the used seal in for the oven for 20 or so mins and see what happens to it. If it does melt/deform, then try it at a lower setting. I guess that'll teach me for over generalizing.

The plastic headlights on my Subaru can survive 220F (~110C) for 20 mins without a mark.. I'm very confident an engine seal won't be affected.

I'm going to do a special run into the shop tonight to clarify this immediately, I'm going to take another look at our oven to conferm the temp scale on it. In my thread I listed my heating temp at 300C.. but, I may have set to it to 300F (150C), because if my memory serves me right there's only one set of numbers printed on the dial. I will keep you guys informed.

Edited by rs25

That sounds like an excellent idea, heat testing with the old seals.

I used to work at a place where we replaced bearings, pressed stators into motor housings, etc. for rebuilding Flygt waste water pumps.

We used the same exact method with heat and dry ice. Whatever parts need to be pressed in is cooled in the dry ice. Where ever it gets pressed into gets heated either in an oven or with a torch. (I DO NOT recommend heating aluminum motorcycle parts with a torch) Makes putting in tight fitting bearings assemblies much much much easier.

If you don't have access to dry ice just cool the parts over night and remove from the freezer just before assembly.

Ok, just got back from the shop, and in FACT our oven is measured in Fahrenheit... it was 300F that I used for my assembly. Fawk, is there a way to go back and edit older posts???

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