What has anyone done to improve the performance of the stock carb?
Maybe by knowing what is wrong with it, we can together improve it without having to purchase a new carb.

 

I have never had any trouble with my stock carb. The only thing i did is add a jet kit to it works great!!! OH and a K&N rigt off the carb.

 

If you never had any problems with the carb, then why did you install a new jet kit?

 

The stock carb doesn't have any "problems" that need to be fixed. It is a good all around carb and is relatively maintainance free. With proper jetting for your conditions and modifications, your not going to have to mes with it.

The "problem" comes from the basic design of the carb. It is what as known as a CV carb. That means that it uses vacume crated by the motor to open the slids in the carb. That need for vacume causes delays in the throttle responce, hence it's not as crisp on acceloration as a "flat slide" The other "problem" is the butterfly style throttle valve that restricts the air flow. It works ok, providing enough flow to run a stock motor, but once modifications start, more air is a nice help.

Manufacturers use CV style carbs because they are easyer to tune and require less maintainance, but you will get better performance from a flat slide style. The trade off is that it takes a closer eye and knowledge of what your doing to keep it running at it's peak.

I'm not saying this to sell carbs, but I just don't see a way to make a CV carb perform as well as a non-CV.

 

I bought it for the performance,it would add to the carb. Quicker response and 5% more power. It also makes jetting very simple!

 

Knutz,

The main reason I stated this question was exactly what your response is:
Poor Bottom End Response.
Why is it that this carb(BSR) is being installed on many atv's and only on the DS is the bottom end performance weak.

Is it maybe not the carb, but poor vacuum signal controlled by a inadequate ignition curve?

sand45,
Why do you think you have better throttle reponse and a measurable 5% increase in power?

 

Because of the large displacement, each stroke of the piston takes such a large volume of air, the vacume can't react quickly enough. Logic would say that the large displacement would create a stronger vacume, but the slide is trying to catch up to the vacume and can't. An added complication to this is the tube from the air box that colapses under acceloration, therefor creating a worse restriction, but that can be helped by the use of a direct mount air filter. You might improve this responce also by trying different strength springs in the diaphram, if they are available. I'm not sure this will work, but it's worth a try.

You will still have the butterfly restricting the flow, so it will not have the capability of an equally sized flat slide.

Personally, I don't think a carb is the first place to look for performance. I have dynoed RWR stage II motors[with the 45MM flat slide] at 48 RWHP, while I get 47RWHP from a Big Gun pipe, Team Pami ignition box, and a K&N filter on the stock carb. I would look to a new carb at about the same time I'd look for a piston and cams.

 

oldmanracing....That is what this jet kit clams better throttle and 5%increase in power.The only real diff is the needle,its shaped thinner and more of a point to it than the stock needle.The jet kit did make a diff on responce and would recomend to anyone.I know that 5% isn't vary much but a little is better than none.

 

Oldmanracing....Also adding a aftermarket exhaust will greatly improve your throttle responce.

 

The bottom end is helped out with a aftermarket pipe,here's a dyno graph on the CT pipe here