Mid size Yam 4strokes

[bubba]

Heya Guys,
After getting a little concerned with seeing smoke come out of my engine exhaust on startup I thought I would contact a Yam dealer to find out if there were any known issues with the Yams. 50 stroke in my case. This is what they sent me:

Yamaha Tech Exchange:
Background
Some reports have been received that the above mentioned models are experience smoke on startup immediately after periods of inactivity (stored or anchor)

Information
When 4-stroke models are innactive (for any lenght of time), they must be trimmed to a positive trim angle (slightly up)

The 4-Stroke engine has an oil pan in which the oil is circulated through the engine for lubrication. While the engine is running, any oil that is on the backside of the piston will be pushed towards the front of the engine. The oil ring performs this pushing action.
When the engine is turned off, the piston motion stops. Therefore any oil left on the backside of the piston will run to the bottom of the cylinder sleeve. If the engine is stored in a level or negative trim position, the oil will puddle against teh piston and rings. In time, this oil will seep past the rings and into the cylinders, thus causing the engine to smoke on startup. This is normal when the oil is allowed to puddle. The only way to stop this from occuring is to trim the engine to a positive trim angle and allow the oil puddle to run towards the front of the engine where it will drain into the oil oan.




Soooo for all those people like me that start there engine in the same position they turn it of... Stop it :P What a pain in the ass...
So much for Yam 4 strokes being cleaner and more smoke free than E-Tecs....

[Craig]

Bubba

Thanks for the information - I noticed mine smoking a bit the other day and wondered what was going on (starting to have horrible thoughts). I had left it sitting unused for a couple of weeks and it was in the "level" position.

So now I know to tilt it out a bit or maybe just use it as an excuse to get out more often.

"Sorry dear, I don't really want to go fishing but if I don't take the boat out the engine will stuff up. Bubba told me so!"

[bubba]

Come on Craig.. You cant use me as an excuse! I use Bear or Dror as my excuse so if she starts calling we are all in the crap!

[bluefin]

There has been so much praise of 4 strokes being cleaner I haven't said anything before. But, I run 4 stroke mowers and on occasions they smoke quite a bit on start up, oil can and does seep past the rings. The rings also have splits in them so you can get them on and off, if these splits line up the engine will smoke for a while! Nothing is perfect!

Howard.

[peter bear]

suzukis do it too.