2005 Honda Rincon running rich

[ch0ch0 bar]

My BIL has a 2005 Honda Rincon 650 with over 8,000 miles on it, and it feels like it's running rich. He's had people riding behind him say they can smell it.

He had a spark plug foul out a while back, and the new one is already getting black with deposits. He's also had to clean the exhaust screen twice because it gets so covered in soot.

He's meticulous about maintenance, like using premium fuel, upgrading the fuel filter, and keeping the air filter clean. The bike runs great otherwise, idles fine, and has plenty of power.

I'm thinking, are these bikes just run rich from the factory? He's thinking about replacing the coolant sensor or the fuel injector, but he'd love to know what others have experienced.

What do you all think? Any advice on where to start looking to solve this?

 

[inapickle44]

I ride out 2006 Rincon 680 ran into a similar issue around 7,500 miles. Strong fuel smell and black plug tips. For me, it turned out to be a lazy coolant temp sensor that was telling the ECU the engine was still cold, so it kept dumping extra fuel.

Swapping that sensor helped a lot. Also, try checking the injector spray pattern if the sensor doesn't fix it. Sounds like your BIL's already doing all the right things with maintenance!