Seized CR

[pairadice]

My son seized the piston in his CR80. WD-40 thru the plug hole overnight was enough to free the piston. What type of damage can I expect when finally disassembled? When the engine siezed he was under throttle and said he noticed a loss of power (of course) and the bike just came to a stop.
I've never done a repair like this so any assistance would be appreciated.

 

[Chili]

Really no way to predict what you'll find. There are different causes for seizure and each will likely cause different levels of damage.

 

[polarishardcorerid]

Probbly the cylinder and i and rings maybe the piston but i dont know for sure

 

[CRazy250]

you probably overheated it, if the piston isnt melted and gouged get a new set of rings and definatly hone the cylinder.

 

[pairadice]

Thanks to all of you for your replies. I will pull the head and cylinder tonight and post my findings tomorrow.

 

[chris61988kb]

how do you sieze a bike anyways, im fairly new to biking so dont laugh at me :nener:

 

[TimberPig]

how do you sieze a bike anyways, im fairly new to biking so dont laugh at me :nener:

There's many different ways, but they all result in damage to the crank/rod/piston/rings/cylinder/head, sometimes cases. Any or all of these parts may be affected. Overheating, lack of lube, inadequate warmup, mechanical failure and others are all causes of seizing a bike engine.

 

[pairadice]

First I would like to thank everyone for their input. Took me awhile to get back to you. The engine had no damage what so ever! WD-40 in the plug hole loosened everything up. Pulled the cylinder head and barrel off. Honed the cylinder and reassembled with a new ring.
I have a friend who at one time was one of the top team mechanics. He said that air leaks are the no. 1 reason for engine seize. With this having been said I made blockoff's for the intake and exhaust and pulled vacuum on the engine with a mighty-vac. No leaks! I will try to start the little beast tonight.