I noticed today that when I'm really getting on the throttle my 400EX, let off the throttle, and then jump on it again, it puffs a quick puff of blue smoke? It's a 2001, probably 500 miles or so. Break in period is done. Had first service done a few days ago. Anybody else experience this? I think I'm just running a bit rich, but I could be wrong. Any input would be great.

Thanks.

 

Blue smoke is an indication that oil is getting past the rings and into the combustion chamber. In other words it's burning oil. Warranty time.

 

That could be I guess, but it doesn't do it all the time. When I run up through the gears and stay on the power all the time, it doesn't do it. But on the other hand, if I sit in nuetral and give it a quick rev, when I let off the gas, it with give a quick blue puff.

 

If it's stil under warranty I would take it in. It'll only get worse with time. Sounds like you either got a bad oil ring from the factory or the cylinder was not properly crosshatched. Even if the dealer can't duplicate the blue smoke at least you have it on record for later useage. If the motor dies after the warranty expires, maybe you can get them to policy adjust it. If it's no longer under warranty, start saving your pennies now for a 440 kit.

 

Let me guess, you're running 10w-40 oil in it...

I believe Gabe (on this board) was the first to suggest running a heavier oil in the machine (specifically mobil 1 15w-50).

The 400ex runs quite hot and quickly breaks down the 10w-40 weight oil. Tons of people have run into this problem (search "oil" in the honda forum).

There almost surely isn't any problem with your machine, just switch to the heavier oil. I had exactly the same symptoms as you, did the switch and its all better now.

ogre

 

Don't worry, I had the exact thing happen to mine. I put 15w50 mobil 1 synthetic in it and guess what, no more smoke when coming back on the gas. I know a guy who forgot to put his filter back on when he cleaned it, and went with no airbox lid. He drove in dysty conditions, and in long grass and cattials, a bunch of dirt went in his engine. It is still running, but it smokes a lot and burns a quart of oil each time he goes out. This in a 99 modle, and has been running over 2 years like this. Just telling you how reliable these engings are even when the piston and cylender wall is damaged. by the way, he is going to put a 416 kit in it soon. But yours in not like this.
I guess the 400ex runs hot and needs heavier oil than 10w40, which the owners manual says.