burnt marks on piston

[mattyboy]

The spark plug was looking a little white so I decided to take a look with exhaust off at the piston of my 365 x torq which i have modded to make a 372. I can see 2 burnt areas just under the ring either side of centre. I cannot see any vertical scoring at all though.

 

I then checked the boot clamp and the cross headed screw that holds it on tight was wayyy loose so i tightened it up.

 

What are your thoughts guys? new piston? Its not done much work a couple of weeks felling big stuff for harvester.

[Ray1]

Sure its not just blow by?

[mattyboy]

Whats blow by? I assume nothing to worry about?

[spudulike]

Sounds like blow by - the exhaust gases being forced passed the ring enough to form a brown black haze beneath the ring - reasonably common and not an issue if the piston is OK.

 

The reason for changing the piston would be wear, piston slap, low compression or scoring. If the compression is still OK then leave it and enjoy. The 365 has never been a high comp machine so expect around 145psi on the gauge!.

[mattyboy]

yeah it does sound like that. saw seems fine. thanks guys