KX65 new cylinder marks

[mike-evans]

My lads KX65 is on 5 hours after a full rebuild including cylinder replate.
I fitted an A piston.
Pulled the front pipe after yesterdays ride so I could look into the cylinder, there is a few rub marks as you can see in the picture. Theres no depth to any of the rub marks.
Air filter has been cleaned and oiled before every ride.

Your thoughts?

 

[Rich Rohrich]

Mike if you are getting wear or seizure marks on the intake side of the piston and no where else it is almost always a sign of a lack of lubrication. Whether the pre-mix separated in the tank, you didn't have enough oil to start with, the fuel had water in it (very common with ethanol blends) or you got the air filter wet cleaning the bike. This has the ear marks of a lubrication issue. If you have multi-point wear in the barrel or four corner wear then you likely have other issues.

 

[mike-evans]

Just on the intake side mate. Currently running 32:1 but manual says 40:1, should I up it?

I mix 125 ml in a 5l can and shake it well before putting it into the tank.

Filter is always out and a filter cover fitted before washing.

No other marks at all on the cylinder.

Whats your thoughts on head colour and piston wash?

 

[mike-evans]

Just to add, theres no marks/scratches on the intake side of the piston.

The piston Ive used is a Mitaka and it cam with a coating, apparently to help the break in procedure and subsequently wears off.... this is pretty much still in place on the piston

 

[mike-evans]

Error in the above post on 2t ratio,I'm currently running 40:1 but manual says 32:1

 

[Pete Payne]

It looks like the dome of the piston has some small marks in it ? ? ?
Did you properly check the piston to cylinder clearance before assembly?