cr80 piston eater

rik220 · Renault 5 Driver Joined: 02 Feb 2007 Karma :

my cr80 has just shattered its 2nd piston. it got a top end rebuild in december after the 1st piston shattering, that time it shattered on the side the exhaust port is on. however about 2 weeks ago it lost power, cut out and lost compression. i only got the cylinder off this week to take a look and its shattered on the other side now. i cant keep up with it eating pistons. i was wondering what the reasons would be for the piston shattering?
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Honda x8r. Aprilia Rs50
Honda CR85
Renault Clio 1.2

Gazdaman · I did a trackday!!! Joined: 12 Aug 2004 Karma :

I'd check the timing firstly. If it's advanced too far you'll get detonation, which is likened to hitting the piston with a hammer, rather than pushing it down smoothly.

I assume you take the time to warm the bike up aswell?

Gaz

rik220 · Renault 5 Driver Joined: 02 Feb 2007 Karma :

yes i let it tick over for a good while before riding it, between 3-5 minutes. when i go on it i dont rev it hard for a minute or two.
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Honda x8r. Aprilia Rs50
Honda CR85
Renault Clio 1.2

0ddball · World Chat Champion Joined: 15 Jul 2005 Karma :

Are you completely sure you did it right when you're rebuilt it or did you just 'have a go'? Sorry to insult your knowledge but a lot of 2 stroke engine problems are caused but people, usually 16 year olds, having a fiddle without really having a clue what they are doing.

What premix ratio are you using? Is the exhaust a genuine CR item and not something from another bike bodged on?

rik220 · Renault 5 Driver Joined: 02 Feb 2007 Karma :

everything was done right. the exhaust is a proper cr exhaust, nothing was bodged. i run it on 40:1
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Honda x8r. Aprilia Rs50
Honda CR85
Renault Clio 1.2

cagiva gezzer · World Chat Champion Joined: 17 Mar 2003 Karma :

Too large clearances will shatter skirts.
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"because one stroke isnt enough and four strokes waste two"

rik220 · Renault 5 Driver Joined: 02 Feb 2007 Karma :

Yea, i know what you mean. Piston slap breaks pistons, but with a top end rebuild just before christmas you wouldnt imagine there being piston slap already?
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Honda x8r. Aprilia Rs50
Honda CR85
Renault Clio 1.2

befdelta7 · Brolly Dolly Joined: 24 Aug 2006 Karma :

HAPPENED TO MY MATE TODAY AND HIS ENGINE WAS RUNNING WELL LEAN, CHECK YOUR CARB SETTINGS MATE Thumbs Up

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Dont do a wheelie in front of a traffic copper... it gets you 3pts and £220 fine.