pressing crank into cases, best ways

13 replies to this topic

Posted January 28, 2005 - 12:44 AM


ok, so ive got my motor apart, still. i put in new crank bearings, bearing on the big end of the rod, and some other things. well, im at the point where i needa press the crank into the cases. i was wondering if there is an easy way to do this at home, without having to take it to a shop to get it pressed in. also, as im putting my motor back together, does anyone have any helpful hints on what i might have a problem with. bottom end, trans, top end. i also got a hi-comp piston and a hot cams exhaust cam. what is the best way to break it in? thanks for all the help guys.

  • yzwiley

Posted January 28, 2005 - 08:18 AM


Yup! Use your freezer and a heat gun or something else to warm parts up. No need to use a press if you know how to utilize the properties of metal and how temps expand and shrink.

Word of caution; if you choose to use a torch for your heat supply be very careful around seals and plastic parts. I use a torch myself but I use it on a piece of scrap metal that then transfers the heat to the cases.

Most often I simply put the bearings in the freezer and warm the cases up. The bearings pretty much drop right in. This is also the easies way to install a set of new wheel bearings.

  • s3706

Posted January 28, 2005 - 08:32 AM


I am in the same situation as demonss I am splitting the case on my 00 426. My question is when you get the new bearings in the case do you have to have the crank pressed into those new bearings to get the case halves back together. Also does anyone know a good cheap shop to get my crank rebuilt with a new rod kit. :cry:

  • yzwiley

Posted January 28, 2005 - 09:35 AM


I always have a shop do my cranks. I have them install the crank bearings onto the crank as so I don't take any chances with screwing the crank up. When I put the two halves together I usually do one side at at time. I'll put the crank in the freezer and warm the one crankcase up. The crank then drops right in. I do the same for the other side.

I've done seven motors to date. I've never had a problem with any one of them. The freezer trick has always worked wonderfully for me.



Posted January 30, 2005 - 07:30 PM


i talked to my motor guy and he said that i should jus be able to work the crank into the cases. if anything, use a led mallet and softly tap on the crank. im a little skeptical about that one but he is the man that handles my motor parts(besides the labor) and he builds motors for a living so if it comes down to it maybe ill try that.

s3706, i know you are in texas but LA Sleeve did my crank. i dont think that will help you too much. maybe you can go down to your dealer and ask about local shops.

  • SXP

Posted January 30, 2005 - 07:53 PM


I always have a shop do my cranks. I have them install the crank bearings onto the crank as so I don't take any chances with screwing the crank up.


Huh:rolleyes: ?! So.... if you already have the bearing pressed into the crank and the crank/bearing just nicely drops into the left case, how do you get the two little crank bearing retainers/bolts on?

  • sirthumpalot

Posted January 31, 2005 - 04:45 AM


More than likely there's a special service tool for this. Check with your local dealer. The old freezer/heat gun trick does work but you must be careful to heat evenly, and work quickly! After the parts come in contact with each other they tend heat/cool each other quickly. You're best off if you can put the whole case in the oven so you can heat the whole thing evenly, just don't over do it. Personally if you can get your hands on the special tool and it's not too obscenely priced then that's the way I would go.

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  • FFRacing79

Posted January 31, 2005 - 05:27 AM


My prefered method is to use an aluminum heat sink. Heat up a piece of round stock the size of the bearings inner race and place it on the bearing. After about 30 seconds the race will have expanded enough for the crank to fall into place. Has many applications including those stubborn lower triple clamp bearings. Tdub

  • MC04

Posted January 31, 2005 - 03:39 PM


You guys are scary!

You press the bearings into the case halves with a press. Have the crank in the freezer in a plastic bag. You need to get an old socket or something similar that will sit atop the inner race on the bearing. Heat the socket with a torch. Get it nice and hot. Take the crank out of the freezer and drop it into the bearing. Gotta do it quickly. If you heated it correctly, it will just drop in without having to force anything. You do the same thing with the other side instead you are dropping the case half onto the crank. You might have to tap it lightly with a rubber mallet.

Don't have a press? I wouldn't even try it. If you are gung ho on doing it yourself, have a shop press the mains into the case halves.

  • trailriderjoe

Posted January 31, 2005 - 05:22 PM


Hey guys,
There's a little something you need to keep in mind when pressing any bearing in. You always want to press the bearing in without applying a load thru the balls. Think about it. If the bearing is a press fit ID (over a crank stub) you press on the inner race with a sleeve that fits over the crank end. You never push on the outer race (thus transferring the load thru the balls to the inner race). This same logic applies to bearings going into a case (OD press fit). You always press on the outer race in that case. Make sense!
Any load placed on the side via pressing on the wrong race can brinnel or dent the bearings and races, thus they will qickly go to making noise and inevitably fail.

As far a a crank, I would never PRESS on the crank itself. I've done it taking cranks out and was shocked at the runout I found between the crank halves. The smaller cranks are a far cry easier to twist / bend than most people think.

Dealerships use a puller to pull the crank in via the inner race (hence the above comments). This applies no load thru the crank halves as well no load is applied thru the bearing balls.

Oh and yes coefficients of thermal expansion are a wonderfull thing. Freezing the crank and heating a bearing is an amazing thing to watch/do.

  • thriller

Posted February 05, 2005 - 09:37 PM


I have had good success with the freezer and oven trick. It is in Eric Gorr's Motocross book to do it that way.


Posted February 06, 2005 - 09:00 PM


i froze the bearings then hammered them into the cases. then i froze the crank and was able to work that into the bearings. it was pretty easy. thanks for the help guys.

ive also added a hot cams auto-decomp exhaust cam. it says that i should automatically get .35mm larger shims. should i do this now or should i break in the cam before checking the gap?

  • RC876

Posted February 06, 2005 - 09:08 PM


I have the tools and press to do this but never use them.

I instead place the bearings and crank in seperate bags and place them in the freezer and wait atleast 20 minutes. I place a heat lamp on each side of the cases. If you need to do this faster use a heat gun. Then take the bearings out one at a time and they should fall into the cases. Have a hammer and something the size of the outer race in case you need to tap on it a little. Dont go look for it now have it handy. Then install the other bearing.

Next place the heat lamps back on the cases/bearings and wait till they are good and warm. Then apply your yamabond or case gasket. Then with everything in place and easily accessible remove the crank from the freezer and place it in clutch side of the case half. If you have never done this have a friend hold the case for you. It should fall in easliy. If not put the crank back in the freezer and then heat the cases some more.

Once the crank is installed in the clutch side without waiting put the other case half on the crank and tap into place. Then immediately add all the bolts and snug them lightly. Again without pause turn the case upright and spin the rod. You should be able to move the crank side to side with your finger tips or with a brass hammer. Tap or move it side to side centering it. Spin the rod again and it should move very free. Then do a primary torque of the case bolts and check the rod again. If it doesnt move freely tap it a little and it should free up. Then do the final torque.

This at times can be allmost a holy experience.

Return back to the freezer and get that beer you have been waiting on. :cry:


Posted February 07, 2005 - 08:24 PM


opps, i opened that beer before i started. then another during. then another after. made things a little easier. :cry:

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