2001 Yamaha Smoking

[TahoeDawgZ71]

I've got a 2001 Yamaha (JN6-508832) in the shop. It smokes out of the muffler pretty badly. It gets worse as the engine gets hot. A little history on the vehicle. It came in because of this problem in addition to running poorly. Pulled carburetor off of the engine and soaked it in Chem-Dip to remove all of the gunk. It cleaned up nicely. Re-installed the carb and started driving it. It was running much better but as it warmed up it started smoking and gradually got worse until I stopped. I've checked the valve clearance, compression (150psi), and changed the oil and filled exactly to the full line on the dipstick. The problem still exists. I'm currently running it out in the yard in neutral to try and burn off the excess oil in the muffler but after an hour it doesn't seem to be improving at all. Do any of you Yamaha experts have any suggestions for me? Sorry but I'm completely lost when it comes to anything besides Club Car, especially in the gas powered versions. Thanks in advance.

[Flintrock]

David, couple things stand out from your post:

Refill oil with one quart, don't rely on the dipstick. Did you use more than one? Any oil in air filter housing?

Operating in neutral won't get that muffler hot enough to burn all the oil out. BBQ it or replace.

Oil scraper rings can go bad and cause that problem without loss of compression.

Hope that helps....

[spriddle]

Does the oil smell like gas? Oil may be overfull or too much gas and dumping over into crankcase. Pull the fuel pump, take it apart, and see if it is full of grit since you've already been through the carb. Be careful with the little rubber diaphram so you can reuse it. If problem continues, pull the vent hose going to the air cleaner (in front) which is probably dumping oil into the air box. Plug the end on the air box where the hose went and route the hose to the ground. I had a G16 that was notorious for this problem. Third time around, I simply pulled the hose, plugged off air box, pointed it toward the ground, and forgot about it. You'll need to change the oil if smells like gas. It will also have to run awhile to get all the oil/gas out of the muffler.

[TahoeDawgZ71]

Thanks to you both. Yes I had changed the oil. I put exactly 1 quart in it. Didn't even look at the dipstick. Forgot to mention that before I changed the oil it was slightly overfilled. Just a hair over full. I also cleaned all of the oil out of the air filter box. It was pretty full. I got one of our temp guys to drive it for over an hour and the smoking gradually decreased to nothing. I'm still considering plugging the vent tube though. Excellent idea. For now it's fixed, but this thing has been in our shop a hundred times. Always a different issue. I've been pretty successful about fixing it up until today. It kind of stumped me for a while but I think it's good to go. Gonna drive it a little more tomorrow to see what she does. Thanks again.

[craig tn]

I take my oil and gas filled mufflers to a radiator shop and have them boil it out.

[sho305]

To burn mufflers out you have to keep flooring it, keep hitting the brakes if it has a governor and keep romping on the gas. That will get it hot. Should get bad then go away if you fixed the issue, in say 15min of that treatment then drive easy and cool it off. I have seen sparks come out when its burning inside so note the surface you are on.

Yeah, people love to overfill and yamaha loves to fill the airbox. You just can't do that. I was going to move mine to right in front of the carb, but replacing engine now so not going to. If it pours out it will kill grass.