Do I need to rebuild?

[duserock]

I ran my cart extremely low on oil. when I put oil back in it, it smoked while I ran it. I drained oil and refilled making sure not to overfill. For a month now it smokes while I run it. If I run it for 5 minutes or more it diminishes a little. When I start it after it sits for a while it really smokes for a bit. I checked compression today and it was 165 but I was on cart for a little before so engine was warm. I don't want to blow any smoke while I drive it in my woods and I want my cart as quiet as possible so I'm thinking rebuild is necessary. Could it be valves or plug or something else before I tear into this?? Thanks, Bryan

[sho305]

The usual way 4 stroke yamaha wear out is the oil ring goes bad, then they smoke and burn oil. They still run ok because the compression rings are ok. Rebuild is a good idea but some have just put rings in and honed them. I would not expect it to be like new with just a ring job as by the time it happens a ton of hours are on them. You would have to measure the cylinder for wear.

The smoke at startup could be a valve seal leaking, but not sure its not real common. They seem to smoke more with more rpm for the rings, as the slinger throws more oil then. If you run it low on oil it will smoke less or stop. A few bad people have done that to sell them, so never buy one you didn't check the oil level when you test drove it.

Note if you have a lift the dip stick will not read right. Put one qt in and that would be the right level. If you overfill it will puke into the airbox and may smoke.