1978 Yamaha XS400 Runs Again 

I got one too,the same problems after 1500 km from new, this girls are cursed ,carbs constantly problematic.

1041 Original miles? Nice! I've got a 1980 Special II with 2800 miles, though some of them are aftermarket miles.

I have the same xs400. Also, had a similar issue. One cylinder would run and the other wouldn't. Luckily, mine got fixed with a new spark plug. 🤞🏼

I brought home an 82, cant wait ti get er running?

Oh yhea and the original carb air box has been removed, someone put K&N filters on each carb intake but it has the original stock exhaust pipes and mufflers.

I have a 1982 Yamaha XS400 Special II. And it runs but ides high then low then high and sometimes acts like it wants to “Runaway” even after the engine gets piping hot. I cleaned the carbs (they were caked & clogged) I then had the carbs worked on, put new spark plugs in her, she showed no spark ⚡️ on either cylinders for a while there but cannot get both stabilized to run as a great pair. She seems very cold natured, new battery 🔋 easy to start now, I use only 90 octane non-ethanol gasoline, no gray or blackish exhaust, not running too rich ! Fellas I’m at my wits end 😢. What do I doooooo ?

My XS400 is still sitting in my yard not running. i cant seem to find the parts anywhere.

Hello, What was the problem on this bike, mine is doing the same, and I am fully angry

Is there anyway for me to contact you

It's running too lean

Idle should be 1200 to 1250 rpm, not 12,500!!!! Hahahaha