yz piston problem ????

[ukracer]

just came to change piston on yz 125 03. Everything stock apart from pc pipe. When removed piston it has a very slight flat spot about 3/4mm wide at the exhaust port along length of piston Also it is a vertex piston and it has two small holes drilled into it inline with marks. These are not standard are they? I have read on here people do it for better lubrication. The cylinder looks great though. What should i do. ? Should i drill holes again with new piston? if so any special way? Sorry i am asking a lot but any advice or thoughts greatly appeciated.!!
Thanks

 

[ukracer]

sorry also forgot to add that the bike previously owned by friend had the cylinder nickel plated before new piston . Dont know if this a factor.

 

[elf]

The flat spot on the exaust side is normal, the holes help cool and lubricate the exaust bridge. I cant remember if the stock pistons have holes its been years since I have used a stock piston. If you have a stock piston with no holes you can drill two holes the same size as they were in the vertex piston. use some fine sandpaper around the holes to make sure there are no sharp edges protruding.

 

[yz125_894]

i dont know about the 03 but on my 02 yz125 the holes are stock on there. if you get a wisco there will be holes already drilled there. if they are not they give you instructions on drilling them.

 

[ukracer]

so do i just replace with new piston? or do i need to check the barrel or exhaust bridge ( with the naked eye everything looks fine)

 

[elf]

Just replace the piston if, you cant see anthing or feel any rough spots with your finger.