did I screw up one cylinder?

[rd400canuck]

While i was making sure i wasnt melting piston tops with all my plug chops i discovered my right cyl looks not good compared to the left that looks perfect.

I think I know why... when I was putting the rings in the pistons for this side  i bent the rings an imperceptible amount. The entire ring would just fall into its groove... it would get hung up a but but a light push could get it in. This was the only thing that was difference when putting the two sides together.

Would a ring that cant move freely cause what I'm seeing? There's even places that cross hatching has been worn through... especially about the boost and exhaust ports. All ports on both cyls were chamffered by me.. and the left shows zero wear above ports.

I've order a hone and some NOS Yamaha rings like the ones that came with the pistons. If I give a light hone and replace the rings... should I be ok?

[Striker1423]

Man if that's bad I better just throw  my cylinders away.

When taking rings off or putting them on, you only should open the ring up enough to get them over the piston edge and tucked into the groove. If a ring was bent you'd see it. A bent ring isn't round anymore, it's egg shaped. That requires a lot of force.

A piston goes up and down on its bore millions.of times. A few grooves worn in near ports etc is normal.

[rd400canuck]

im just pissed at myself for using those rings... convinced myself theyd be fine. They were actually bent wavy not out of round,,, causing them to stick in their grooves and not move super freely. The other side is perfect.. not a mark and all the honing marks are there. This side looks like a war zone compared to it.  Plus... I dont have more than 7 tanks of gas through this thing and it already is worn through the honing marks :(

I've order a hone from amazon and am going to find some NOS yamaha rings and give it another go. Hopefully that prevents it from happening so fast again.

[rodneya]

Take some pics of the top and underside of the piston when you have it out. All that carbon and no transfer flow pattern looks lean.

[rd400canuck]

Hi Rod,

I noticed that too.... Ive known the bike to be lean this entire time. Only yesterday or the day before have I even gotten it close but I havent driven it much. Im about to put 170's in it and do a plug chop. The 150's in it are showing lean in plug chops. I plug chop them as well.

I'm going to pull the jug today to make sure the piston is ok and to see if i should replace it. If it needs replaced I'm almost tempted to just get some new Wisecos and put them in. The NOS Yamaha pistons and rings are super expensive.

[Striker1423]

Hi Rod,

I noticed that too.... Ive known the bike to be lean this entire time. Only yesterday or the day before have I even gotten it close but I havent driven it much. Im about to put 170's in it and do a plug chop. The 150's in it are showing lean in plug chops. I plug chop them as well.

I'm going to pull the jug today to make sure the piston is ok and to see if i should replace it. If it needs replaced I'm almost tempted to just get some new Wisecos and put them in. The NOS Yamaha pistons and rings are super expensive.

Wisecos are loud. I can vouch for that. But, ProX is good too. Just check everything first. But, yes if the ring doesn't move freely it's not good.

[rd400canuck]

I decided to just bite the bullet and found another NOS yammy piston and rings. I'll hone the cyl and put the new stuff in. I'm praying after it awhile it looks as good as the other side does and not worn like it is now.

[KANDY]

Man if that's bad I better just throw  my cylinders away.
;D ;D