crank hard to turn after putting cases together

[YZ250Guy]

When I put the two crank halves together the crankshaft is hard to turn. Maybe I should start from the beginning. (All of the following was with new bearings and a new crankshaft) (Hot Rod)
I sent Eric my crank case halves and he installed the bearings.
I then installed the crankshaft in the left bearing using the technic in his book (heat the bearing for 5 minuts, freeze the crankshaft) This worked perfectly and the crank was easy to turn. (It was also on all of the way)
I then assembled the transmission (Still works good after assembly)
I then put on the glue (Hondabond) on one half and assembled (No I did not put on too much)
While installing I did not spin the crankshaft while installing it (Is this the problam and will I have to dissasemble to fix this? The manual did not say anything about doing this)

Any ideas on where I messed up and what I should do to fix it? I have not installed the seals so I know that they could not be the problem. There is nothing in there that I could have messed up. When I got the bolts snug I tried to turn the crankshanft and hit it on both sides to help it setup in the bearings. Did I start too late with this or do you even have to help the bearings setup on the crank? Thanks

 

[Ol'89r]

When I got the bolts snug I tried to turn the crankshanft and hit it on both sides to help it setup in the bearings. Did I start too late with this or do you even have to help the bearings setup on the crank? Thanks

YZ250Guy.

Your right side bearing may not be seated all of the way into the case. Try laying the engine on its right side and take a small hammer and tap the outside of the aluminum boss on the engine case where the right bearing sits. Don't tap it too hard. A nylon hammer works good for this, but sometimes you have to use a regular hammer.

If the crank loosens up when you do this do it again until the crank rotates freely.

Tapping on the end of the crank will seat the crank into the bearings, but will not seat the bearing all of the way into the case. To do this you have to tap against the case itself while the weight of the crank is resting against it.

Hope this helps. :thumb:

 

[YZ250Guy]

I tried to do this but with a plastic/rubber hammer. I don't think that I can hit case right where the bearing is. Do you think if I used a brass drift I could hurt anything? Thanks

I will definitly try again tonight to seat the bearing with the hammer first.

 

[70 marlin]

After you press the cases together. Support the cases on two 4"X4" blocks and gently seat the bearing's in the case. You should be able to look down at the crank through the cases and see which side is binding? I usually thread the nuts on each end of the crank. Then use a plastic dead blow hammer and firmly tap the end of the crank. Be careful not to damage the shaft ends, also you can damage the new crank bearing's if you beat on it hard! Do a few blows, then check to see if you have freed up the spinning assembly. If it still tight, flip it over and do the same thing to the other side. The cases must be supported! Note: you should have all the case bolts in and torqued.

 

[Ol'89r]

I don't think that I can hit case right where the bearing is. Do you think if I used a brass drift I could hurt anything? Thanks

.

YZ250Guy.

That is what I use, a 1/2" diameter brass drift.

Tap the bearing boss all the way around the circumference of the boss. Only tap the meaty or thick part of the boss being careful not to hit the edge of the boss where the seal seats. If the crank does not free up, flip the engine over and do it to the left side. That bearing may have not seated all the way.

Heating the cases up a little around the bearing boss will help.

 

[SULLY]

Just for reference take a look from above. Do the two lobes of the crank have an equal gap between them and the side cases?. After bottom end rebuild it is usually off centre slightly, in whatever direction bearing has the least friction in its respective case. By looking which way off centre it is will give you a clue which way to hit it.

In the final summary though, if you cant get it to turn freely then something is wrong and it needs to come apart again.

 

[JamesB]

Does the manual show how to use a feeler to make sure the crank is not jammed up against the left side case? The crank has to be out a few thousandths so as not to rub the case. When the case halves are put back together ideally the crank will be centered between the halves, ie. no rubbing on either case. I rebuilt (split cases) my buddies Kx125 and when i tightened the case halves together i had the same thing, crank was hard to turn. I hit the rotor side of the crank with a dead blow hammer (this is not the proper way to assemble bottom ends because the crank alignment could be knocked out of spec) and it "centered" the crank enough to allow the motor to spin freely. Good luck..........

 

[TravisP]

the crank needs to be centered in the cases measure with a set of feeler guages to see which way it needs to go get one brass hammer and one regular ball pien use the brass against the crank half that needs to move as so not to ruin threads and hit it with other hammer it should make a distinct clunk when the crank centers itself. Hope this helps