Dave-

I have a YS53FZ that has been running inconsistently. If it is cold, and I start it up, it runs just find. However, once is warms up, it starts to lean out at the top end. I've tried replacing the check valve and diaphram with no luck. More recently, I replaced the fuel line between the pump/regulator and carb with one that is clear. Now when I run it up, I see a lot of bubbles in the fuel line comming in from the pump/regulator side heading to the carb, but I don't see any bubbles comming in from the fuel tank fuel line I think somehow I'm introducing air in the pump/regulator. Is there anything that I can do to fix this?

Thanks

Don Myer

The bubbles are normal. Don't worry about them.
The problem is likely a piston/ring issue which need to visit our service dept for correction.
Send the engine to:

YS Service
1295-C Industrial Court
Gardnerville, NV 89410

Be sure to include a description of the problem.

Thank You,
Dave