Breather box question.

[Gcraay]

I see most people install a small filter or two off the breather box.
1. Is it needed.
2. Is the shape and design of the box critical? Does it have the baffle inside to control something? Is the hole size and position of any importance?

I gots me and idear.

 

[Kathos]

It's all important because it affects power. A less restrictive air box will allow more air into the engine. I don't have stock carbs so I don't know if its enough that you would require new jets. Cone filters offer just about as little resistance as you can get.

 

[gggGary]

I will assume you are talking about the crankcase breather.
This drove Yamaha nuts, they changed the design a bunch of times. Any 360 twin has a tough time controlling breathing (oil mist). The crankcase air volume changes so much as the pistons go up and down together that it acts just like a pump. so.... you may wish to swap up to a later model breather. I don't recall if the 76 is single or dual tube breather. My suggestion is to either send the tube into the air filters or devise a catch can. Many install a little chrome PCV valve/filter to kind of create crankcase vacuum, but I have not tried this.
Please tell us what you end up doing and how it works for you.

 

[gggGary]

This thread covers it pretty well http://www.xs650.com/forum/showthread.php?t=1771

It would be good if you add your ideas, what did or didn't work, there.

 

[racerdave]

I like the brake booster check valve positioned over the pod filters.
The yellow arrow is pointing to mine. You can see it if you look close