on the 4 strokes it doesn't really matter...as long as you make sure the exhaust valve is closed. The crap may run down into the motor but it will not go inside the motor if the exhaust valve is closed.....you can turn the YS motors to TDC and the motor will sort of notch right there....This is the way to store the motor...This way you don't have a valve spring compressed...and the valves are closed.....I would not as a practice store it on its nose....I store my stuff horizontal....but if you must I would say you should be OK because the valve would be closed.....Now if you don't make the sure the valve is closed then....well its not a good idea.

On the 2 strokes there is much more of an issue with combustion by products and even a small amount unburnt fuel....With the 2 stokes it can cause problems with bearings and so on...

The 2 strokes have more of this unburnt fuel and crap in the pipes....The 4 strokes tend to be hotter in the exhaust and the unburnt fuel that slips by tends to vaporize a little better in the pipes because of the temps....

Not to say that the 4 stroke does not have this issue...its just less of an issue...My opinion.


Troy Newman