I got all the parts for the tranny on my '95 Scrammy, and was putting the tranny back together yesterday. While installing the tranny I had to pull the carb to get the tranny in - I don't know why I didn't have to pull it to get it out - just one of those things.

Anyways, when I got the carb off, I noticed the Scrammy has a boost bottle on the intake boot (adapter is what Polaris calls it). A few years ago when I had my Banshee, a boost bottle is one of the things I added to help performance - and I had never thought of one on a Polaris. I got to digging around on Partsland and come to find out only the '95 and '96 Scrammys had this.

The bottle I put on the 'shee made a noticable difference on the low end, would a bottle on the Scrambler not do the same? And why did they stop putting the bottle on the Scrambler?

 

The boost bottle on the banshee just helps balance the two cylinders out on the bottom end from what I understand. Other than that I dont believe they make any difference. All the drag only bikes do away with them. Interesting on the Scrammy. Maybe a good place to plumb in some nitrous?[img]i/expressions/face-icon-small-happy.gif[/img]

 

Yamaha Tri-z's (single cylinder 250cc three wheeler) had boost bottles. Also, I bought a YZ490 that had a boost bottle added to in back in the late 80's.

On the banshee (and all other two strokes I guess), a PROPERLY sized boost bottle will help power and response. THis size changes depending on mods and rpm range.

 

So Richard, why the need for a boost bottle on a single when it is not a vacuum reserve like the 4-stokes? Is it pressure wave return or a balance to the pulse of incoming fuel? That strikes a curiosity that I'm sure someone will know the answer to.

 

Sorry, I didn't get to that part in my post. MY UNDERSTANDING (which may not be exactly right) is that it is supposed to control the pulse. On the banshee, it just happens to use the pulse from the other cylinder to smooth it out. On a single cylinder, the intake of air creates a vacumn inside the bottle that pulls a small amount of air into the bottle when the reeds close. Then the reeds open and air flows again. This keeps the air flowing and doesn't stop abruptly when the reeds close.

If I remember right, Trinity is supposed to have a long explanation of boost bottles on their website. I haven't read it though.