350X Smokes on start-up

[Yamaha Tri-Moto]

So when I first got my 350x the idle was a bit sporadic and took a while to come down to idle. It would also stall sometimes when I would coast with the clutch pulled in.

I adjusted the vales to spec and have not had any of the above issues since I've done that.

The only issue I have now is it smokes on start-up for 4 or 5 seconds (choke fully on) and goes away real quick (I don't think it did this before I adjusted the valves)

Is this anything I need to worry about? I'm used to the smoke on 2 stokes, not sure about old 4 strokes.

[BOB MARLIN]

Usually if it smokes only on start up is a valve seal issue. When the trike is shut off there is oil up in the head that eventually seeps down the valve stem. Once you start it again it burns it off. I've had the same problem after switching to a full synthetic oil. If I used plain oil it was fine, but the synthetic oil does such a good job at cleaning everything it finds every way posable to seep through. Switching back to regular oil was too late. Put new valve seals in and all the smoke went away.

[Yamaha Tri-Moto]

Usually if it smokes only on start up is a valve seal issue. When the trike is shut off there is oil up in the head that eventually seeps down the valve stem. Once you start it again it burns it off. I've had the same problem after switching to a full synthetic oil. If I used plain oil it was fine, but the synthetic oil does such a good job at cleaning everything it finds every way posable to seep through. Switching back to regular oil was too late. Put new valve seals in and all the smoke went away.

I bought a set of new valve seals but have not attempted to install them yet. Is it a hard job? Will it cause any issues if I hold off on changing them?

I just find it strange that it only started smoking right after I adjusted the valves. But it fixed the other issues I was having.

[BOB MARLIN]

It might not be the seals, I just wanted to point out that your symptoms can be caused by seals. If it smoked all the time it points more to piston rings. I don't know if you can do the seals without pulling the head. You have to get the valve springs off to change them. The seals themselves are easy, getting to them not so much. I don't think it will hurt anything if you just leave it the way it is. If the smoke on start up doesn't bother you.

[Yamaha Tri-Moto]

It might not be the seals, I just wanted to point out that your symptoms can be caused by seals. If it smoked all the time it points more to piston rings. I don't know if you can do the seals without pulling the head. You have to get the valve springs off to change them. The seals themselves are easy, getting to them not so much. I don't think it will hurt anything if you just leave it the way it is. If the smoke on start up doesn't bother you.

Thanks for the help, it runs and starts too damn good to mess with it now. Just gonna send it 🤘267029

[yaegerb]

It could be rings or valve seals. Take a compression check. Then drop a teaspoon of oil in the spark plug hole and retest. Did the compression increase? If so, your rings are going bad. If compression remained the same it’s your seals.