Sorry to see this. Not good.


The bearing is probably made of harder steel than the crankshaft. It is more likely that the crankshaft suffered if the bearing temporary seized, causing the crankshaft to rotate in the inner bearing race. Sorry.

I would not rule out completely the chance of something else being responsible for the vibrations. Obviously you need to address this problem, but please take a good look at everything else to be sure.

Weird though… I would have expected the crankshaft to have welded itself to the bearing race by now. I have twice seen similar things, in one case the inner bearing race of a wheel bearing was welded to the axle after a temporary bearing seizure, and in the other case a primary sprocket had welded itself on a crankshaft after the key had snapped. Not the main bearings on a crankshaft in either case though. I remember that several years ago some of the GASGAS two-stroke enduro models had a flaw, the crankshafts could slide side-to-side in the main bearings, or at least one of them. I don’t think there was any noticeable play, but at least some of the flawed engines did run fine for a long time…. Guess the friction in the bearing itself was less than the friction between the crankshaft and inner bearing races given the pressure put on the crankshaft in a running engine...

yes, its not good is it

I need to take a look at the other side, I got the alternator rotor nut off (bastard tight as it should be) now all I need is a suitable puller, can anyone recomend where I can get one, or dimensions to make one

I'm in two minds what to do about the main bearings on the crank, obviously a full bottom end rebuild is needed but as we are in the middle of summer I may try a short term fix - get some very strong thread lock and squirt between the inner race and crank.
If glueing the bearing to the crank works then I'll leave the rebuild till the winter. it should also diagnose if this is where the vibration is coming from. it could be that the motor gets to certain revs then the crank starts oscillating in the bearing.

cheers for all the help so far from everyone

undo the 3 allen head bolts that hold it to the starter clutch and use them in the 3 threaded holes in the flywheel you might need to rotate the starter clutch so there is something behind all 3 of them threaded holes then tighten those bolts staggering the sequence so you apply even pressure put the main nut on the end of the crank a few threads and give it a tap when you have quite a bit of tension on those 3 bolts it should shock it free.

my bikes kick only....so no sprag clutch...can I still wind some M8 bolts through the 3 holes, what will they press against?

cheers

my bad thought you had e/start and kick :oops2:
post a pic and ill work it out from that :thumbup1:

looks like something like this is needed

http://lh5.ggpht.com/_aJzSBN66Sc0/Sl...800/001499.gif,
actually I think I have something like that buried somewhere....

i meant post a pic of your engine :innocent: :rofl:

i got a puller same as that from machine mart tho :cool4:

flywheel puller
 

I found my puller and have it on the flywheel, I've done it up 'kin tight but nothings moving.

any tips? I've tried a bit of heat, but don't want to resort to hammer.

cheers

as long as you protect the threads using a hammer is not a problem it probably just needs a whack to shock it free if your puller is similar to the one in the pic give it some torque and then give that center bolt a big 'kin whack i'd put the end nut loose on the crank so when it comes free it doesn't come flying off.

pulling flywheel off
 

I tried more heat whilst under tension from the puller and it flew off with a bang. -I didn't leave the nut on....doh

the bearing that side is seems OK, I'm gonna use the thread lock to hold the crank in the bearing on the other side and see what its like.

what about the big end - can it be checked without taking top end off.

cheers

only if you have a dial gauge with an extension rod but you might be able to knock something up with an old spark plug a rod and a ruler to measure any backlash.