Under the motor between the frame rails you will see a large round disk with a hex head in the middle of it, I believe you need an 18mm socket to take it off.
The spark plug gap for a Yamaha Big Bear 400 should be set at .024 inches. A new spark plug may be purchased at an auto parts store with the gap preset.
The oil capacity for the Yamaha Big Bear 400 is 3.2 quarts. It is recommended you use 10w30 oil in the Big Bear.
What is the spark plug gap setting for a 1987 yamaha big bear
yamalube 10w30
3.2 quarts
1999
on the left frame in front of the engine.
If one is interested in learning about the Yamaha Big Bear 400 the best place to go would be to the Yamaha website. The individual(s) could also go to their local Yamaha store in their area and the salesmen there could share a wealth of knowledge with them on this topic.
.032
58 foot pounds
To set the idle, adjust the carburetor.
gap for my 1995 big bear 350 is 0.6-0.7 mm or .024-.028 in.