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4RT - black smoke

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My 2016 4RT with 40 hours on the clock makes a bit of black smoke when I rev her. Runs great, lovely machine, starts easy. Full disclosure: I’m a lazy man, full maintenance done when I bought her with 10 hours on the clock. Nothing since other than cleaned and oiled the air filter about ten hours ago. Time for valve tuning? Too much oil on filter? Trade for a 2019?

 

As a general rule of thumb black smoke is unburned fuel. White smoke is oil. Sounds like your fuel injection might be a bit rich on top but if the bike runs good why worry.  

All my 4rt’s haven given a whiff of black smoke when reved hard - especially when in the garage and messing with them .

Think it’s  just fuel as said above.

Get into habit of fresh air filter every ride ( cleaned and oiled)

11 hours ago, lineaway said:

Well, they did go to 3 rings in 2017.

All the 4RT 250cc & 260cc engines from 2005 to present have used 3 rings. The only engine that ever used 2 rings was the 2016 (first year) 300RR.

Nothing to do with piston or rings. Take it apart and clean it, the throttle body and air box manifold will be black with carbon, not to mention oil in the bottom of the air box if it's been upside down. No wonder it's smoky

I had a little of that on my 07 4RT, as jrsunt said I cleaned it out, checked the valve clearance (was good) and changed the plug and it went back to normal again.  

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