I have a 2014 Honda 420 with the DCT transmission. I had he engine rebored and re-built last year and it has run fine. Recently changed the oil and rode it to the top of the mountain and back with no problems. Yesterday took it out of the garage and ran it across the fields and it was smoking. The air filter was covered in oil from blow back. I thought as these machines are notorious about filling the oil as the transmission and oil work together maybe I added to much. I checked my empty bottle and had put in the correct amount of around 3.5-3.8 qts.
I did not roll it but did climb one very steep hill at the top but it did not smoke on the way down.
So I pulled the new plug it had soot on it and reinstalled cleaned the air filter and installed.
Still smoking and have black suit in the tail pipe. Oil level comes up when I take off the fill cap and can see it. Turn off drains down and shows about 1/4 way up stick after checking.
I am at a loss on this and hope its simple. I hate to think I have to get the engine again as it was bored over twice.
Any suggestions?

 

A single cylinder 420cc engine blows 420cc of air out of the crankcase as the piston goes down and sucks it back in as the piston rises. Honda crankcase baffles are pretty good, but you may just have gone on too much of a slope and, once the breather intake in the sump is covered, it would pump oil into the airbox with every downstroke. I would try to get the oil out of the filter and airbox, then use the bike for a while. I once rebuilt the top end on a Suzuki which had "lost" the entire piston skirt, it was making masses of smoke, and continued to do so with the new piston fitted, until all oil had been burnt out of the exhaust. It took a long run for this to occur. The piston may have picked up or broken, but give it a chance to recover before starting another rebuild.

 

Brilliant reply sir.
Any way to check the baffle and I was thinking of doing a compression test. I drug the machine back from the farm and have cleaned the filter. There was no oil back in the intake and all oil was just dripping from bottom of filter kinda like honey. Breather was oily but normal.

 

Also the muffler has a black dry soot and the new plug was fouled.
I had tuned it up and ran it for a good 3 hours no problem after tune up and oil change. With the DCT I put in 3.5 quarts.

 

The crankcase baffle system on a Honda is just a labyrinth, I assume so that oil does not get far enough into it to get shoved into the pipe going to the airbox, no one way valves like Briggs & Stratton singles have. As I wrote above, use it, and see if the oil smoke clears.

 

Not able to ride but been letting it run for 30 minutes every night slow revs still smoking. Added some sea foam for good measure. Thank you