250 sho cylinder pitting

[mccutch2u]

Have any of you experienced pitting in the plasma cylinders of the Yamaha sho motors? Had a friend contact someone with Yamaha tech services and they have seen it but don’t know what the cause is. 450-500 hundred hours and the motor started Smoking at idle leak down shows 12% and compression was 150. Pulled the head and found one cylinder with pitting on the cylinder walls. Piston top and head and valves in great shape. Yamaha said it would have been covered but it is out of warranty.

[baja200merk]

Yep have pics of them so rotten a couple started talking to the adjacent cyls. I’ll dig up the pics tomorrow they were also low hour “plasma” cyl 4.2L. If any salt makes it to that cyl the “plasma” seems to remove itself from the aluminum sleeve rendering the block useless unless a steel sleeve is installed. Most can be saved with steel sleeves but it’s not cheap or easy.

[johnboy 88 vegas]

The newer these motors get the more they become throw away motors. They are good reliable engines unless something goes wrong with corrosion usually. We have rebuilt a few of them but the bore has to be pristine just so you can run a diamond hone through it for factory rings. I would really like to know what the "plasma" coating is made of since they wont tell me over the phone.

[mccutch2u]

I spoke to a company that does nikasil and they said they can repair the cylinders but I would have to find oversized positions. Nikasil is used on a lot of the motorcycle engines I have had built and never had an issue.

[baja200merk]

Wiseco will make you pistons if you order enough of them. They worked great in the f115 and f150s I’ve built.

$380 for a rod and piston assembly from Yamaha is ridiculous.