Onan 20hp twin playing Puff the Magic Dragon

[cdsl810 181]

I'm suddenly getting gray/white smoke on startup, and it is slow to start. This only happens when it is cold and hasn't been run in several days. I haven't had any issues with slow/hard starting ever. It's a 1990 with 550 hours on it. Does this seem like a carb issue or something else like valves, etc..? I humbly ask the experts.

Edited September 7, 2013 by cdsl810

[WH nut 553]

When was the last time you put plugs in it. Gray/white isn't that big an issue, maybe a little flooded.

[cdsl810 181]

I changed the plugs and wires about 20 hours ago. It had been running great up until now. I will pull the plugs and see if they are getting fouled/flooded. I used NGK plugs for the first time, TR4 or TR5 I think. Thanks for pointing me in the right direction. WH nut

[Red-Bovine 334]

I would check the compression. You may have a loose valve seat. My 520H always started hard when this happened. I repaired the valves on several occasions and finally replaced the motor with a Honda GX630. If you can fix or get it fixed, the Onan is a good motor. I like the Honda, but the Onan was a great motor when running right. Just too problematic for me.

 

Red

Edited September 7, 2013 by Red-Bovine

[cdsl810 181]

Compression is 120 front and rear. It seems the issue was with the plugs: NGK TR5. I replaced the plugs, which only lasted 15 hours. All is well. I'm trying e3.48 plugs this time (got them for the same price as Champions). I will keep a close watch on the carb and see if it is running too rich and causing the plugs to foul. So far, it is running smoothly with no rich "smell".

[546cowboy 302]

That's why I always put the originals in everything I own. I tried some of those double electrode plugs in my truck once years ago and changed back to OEM the next day. Lesson learned!