Really stuck on this one!! Please help

[Tom_N]

Hello i am posting this on behalf of my friend who has a 2001 Honda cr80. One day he was on the cr 80 he lost all power and the wheel locked. he tried to kickstart it again but the kickstart was impossible to move with full weight on it. So i immediatly thought seized, we took the cylinder apart to find that half of the bottom of the piston had cracked and broken off. He bought a new piston and put it in. when he tried to kick it the kick start moved fine but the bike didnt start, when he tried to kick it again the kickstart was impossible to move again!! he tried bump starting it but the back wheel just locks up. I have told him that the bit of the piston that broke and fell off could be wedged between some sprockets and stopping the bike from running properly but he has said that he has checked and there is no more bits of piston in there . So what could the problem be?
Cheers
Tam

[Timmeh]

The bike's suffered a full-on seizure.

Chances are that the cylinder's been scored to fuck and the piston rings (however new) aren't fitting snugly anymore, causing a total loss of compression and an engine that's next to useless.

Also the shock of the rear locking under load could have broken all sorts of bits in the gearbox. Forks, selector, bearings and gear wheels are all prone to breaking.

I'd hunt around for another engine/box if I were you mate. The cost of replacing all the parts is prolly the same.
____________________
GSXR400 x2 | '94 RVF400 | '93 TZR125 4DL (again)
20:22:30 BLUEX5: i would love to be forced to undergo a**l plugging with different sizes
20:48:18 Temeluchus: comp you hunk of smouldering homos3x you

[finpos]

I think you've correctly identified that something has broken again

finpos.

[Paddy Blake]

He should have got it rebored as Timmeh said the cylinder will be scored.
Take it apart again and check for bits that may have left in there and
check the small and big end bearings and also the main bearings.

Paddy.

[Tom_N]

[Tom_N]

[finpos]

From what you say, sounds like some bit of debris has got stuck in the gearbox/primary drive the other side of the clutch (4 stroke?).

If he still has the top off, see if he can move the piston with it in by hand (might have to spin the rear wheel at the same time)

But, who can tell

finpos.

[Tom_N]

[Pete.]

Take off the right-hand engine casing and see if there's something come adrift in the primary drive/clutch area. Also try turning the crank by the end-bolt with a socket. If it won't budge try pulling in the clutch and turning it again. If it does with the clutch pulled in your gearbox has broke.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Tom_N]

I was at his house looking at it,we took the casing off and turned the nut. The piston moves up to the very top of the cylinder but wont go back down. It only gets stuck right at the top of it's stroke!! what is this?
Cheers
Tam

[finpos]

Incorrect base or head gaskets? i.e. your cylinder is too short for it's stroke.

finpos.

[Pete.]

It would never have been running in the first place.

Sounds like you need to pull the head off, should only take a few minutes.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good