[Phoenix]

Hello!

2014 Ninja 300 ABS, when accelerating everything is smooth and sounds sexy. No issues when flooring it.
When holding a steady speed the engine sounds like brrrnrnrnrnrnnrnrnrrnrnrnr, like the throttle quickly kicking on and off, rather than a nice constant brrrrrrrrrrrrrrrrrr. It sounds like what I'd imagine the fuel system mapped to run really rich (previous owners used it as a track bike) or maybe a spark plug issue but I have absolutely ZERO problems accelerating super slowly or really aggressively, issue arises ONLY when maintaining a constant speed. Sometimes the choppiness is strong enough to create a noticeable vibration.

Stock exhaust installed but I think previous owners used aftermarket exhaust, maybe they fuel mapped it to match their exhaust? I am completely illiterate when it comes to fuel mapping/basically anything other than oil change type maintenance so I am unaware of the impact that may have.
Bike has been dropped at least twice, pretty bad rash on the exhaust and a scrape on the engine cover on the other side. Complication due to previous crashes? I don't know.

 

[jkv45]

Take a look at the air filter. Just over-oiling it can make it run rich. Pull the filter and take a short ride to see if removing it made the issue better or worse. If it made it better it tells you it's running significantly rich.

How old is the gas? If the tank has been left low, and the temps have changed, you can pick-up a lot of condensation that will mess with fueling.

I'd also run a strong fuel system cleaner like Techron Concentrate (1oz per gal) now and once a year to keep the injectors, valves, and combustion chamber clear of deposits.

It could be possible the PO did a remap/flash of the ECU to better match his set-up, but try the simple stuff first.

You can also look at the plugs to see if they show a consistent rich mixture.

 

[DavZ]

I once had a similar problem (on a different make/model of bike) and I was shocked to learn that it was stiff links in the chain. I had the chain replaced and the problem went away. It bugged me so much and I couldn't figure it out that I brought the bike into a shop. The mechanic said - "replace the chain" -- and it worked. I didn't feel it when I pushed the bike - I didn't have any issue with acceleration. Only when riding at a steady speed, the bike pulsed annoyingly - like the engine was bogging on one of its 4 cylinders.

 

[MAL]

....I was shocked to learn that it was stiff links in the chain. I had the chain replaced and the problem went away....

Interesting!
Especially so, because OP posted pictures of a suspect looking chain right here: JUICY Road Rash Repair, Advice Needed!

 

[jkv45]

Interesting!
Especially so, because OP posted pictures of a suspect looking chain right here: JUICY Road Rash Repair, Advice Needed!

I see what you mean -

Good call on the chain DavZ!

Even if that's not the problem, it is a problem and should be replaced.

 

[DavZ]

And I can say that my chain, before being replaced, did not look as bad as the one pictured. I double vote that your problem is your chain. You can see links kinked up and down in the photos. It should be smoothly slacked where unsupported.