Piston slap?

[Xero]

Well, I went into the garage tonight to take a look, i took the jug off to find their was nothing up with the top end, but the bottom is pretty much siezed, it takes pretty much my full strenght to get the engine to turn, i dont know what to do or what to replace as ive NEVER been into a bottom end, i hadnt even been into a top end until i got this damn blaster.. advise? :S

I only noticed the noise when i got into 4th gear and was close to going into 5th, it sounded like a knocking noise, but was acctually running fine, or seemed to be other than the noise and white smoke, it got me close to my trailer fine until the chain snapped...

 

[scotj77]

Ahhh the bearings are going bad or something is in there. does the tranny turn in neutral?

 

[Longview]

One of the Main bearings maybe?

If there's no problem shifting through gears, i wouldn't think there is anything in there.

 

[scotj77]

wait the chain snapped? is your rear brake frozen or the axle bearings shot? was it putting strain on the motor? or did the engine seize and break the chan?

 

[Xero]

The chain snapping was really anything to do with the rest, the rest of the bike is fine except that.

 

[best]

OK, let's think this through:
White smoke: no coolant, so must be burning gear oil. Has to be leaking into the engine from somewhere? Crank seal or engine case seam? Bad crank seal is often caused by bearings going bad. Engine case seam leaks are either bolts came loose or damage like from a piston skirt, but your piston skirts are fine? Check them for cracks and missing pieces.

Knocking noise in 4th&5th until the chain snapped: Sounds like a labouring engine overheating and detonating. Chain breaking occurs from derailing and twisting, worn out and failing or severely loaded (as suggested rear bearing bad or brake stuck on). This could load the motor enough to have it detonate. A bad crank main bearing can also make a knocking noise, and is stressed by the extra load of something like a brake stuck on. A bad crank bearing would cause the engine to be hard to turn over (not always!) and white smoke.

Just a guess on my part Steven, you have a bad crank bearing, but also check your front and rear brakes for sticking (does it roll freely?) and your rear axle bearings (looseness, freeplay, binding).

Weekend riding may be out, you may soon become a bottom end expert whether you want to or not... Hard to be sure from here. Hopefully I am wrong.

 

[Xero]

Can it he done, and how hard of a job is it to change the crank bearings? All brakes and stuff are good as I pushed it part of the way back to the trailer...

 

[best]

Can it he done, and how hard of a job is it to change the crank bearings? All brakes and stuff are good as I pushed it part of the way back to the trailer...

It is a moderately hard job.
Motor has to come out of the frame (my son did that in 13 minutes Saturday!).
Motor has to be cleaned and split, some special tools needed. Flywheel puller, and home-made case press (a bar and some long bolts).
Bearings pulled off the crank and new ones installed, if the rod bearing is bad (very likely) you will need a new or rebuilt crank.
New seals and gaskets needed too.

Can be done in an afternoon. MUCH cheaper to buy the tools and do it yourself.
If you take it to a shop it saves money to remove the engine from the frame and clean it before delivery.

NOT a clean motor...