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head porting
- kzz1p
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- larrycavan
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27 Jun 2009 20:00 #302578
by larrycavan
Replied by larrycavan on topic head porting
IMO, CV carbs are fine, up to a point. Jetted properly they'are nice carburetor but when it comes right down to it, they don't hold a candle to a good rack of mechanical slide smoothbore carbs for acceleration and all out power.
Throw a semi serious cam into the equation and sometimes CV carbs can be a real treat to get dialed in for good street behavior. To me, they're just not worth the time, effort and money when really good performance carbs are available.
They are a band-aid approach to performance that the factory needed in order to meet emissions and improve performance on stock machines.
The cross sectional are of a CV carb at the throat is one thing. You also have to take into consideration the throttle rod and the throttle plate. Both are flow killers. As such, you need the carb larger than a mechanical slide arrangement.
If I was going to do something serious and had to use CV carbs, the throttle rod would get halved and thinner throttle plates installed to improve flow. Same as the bored fuel injection throttle bodies.
The key thing with mechanical slide carbs is to not go too large. Get the right size on the motor and it's a pure joy to ride. Go too big with them and it's all up to the rider matching the throttle position to the rpm the motor is at.
A 1075cc street motor where midrange is primary focus will work very well with 31mm CRS carbs. For a 1015 or 903 street motor [same criteria] 29's. When you get to 1200cc, then jump to CRS33's or RS34.
Electronic Fuel Injection is all about throttle response. Fuel injection is no guarantee of improved HP. Often in certain classes of racing, carburetors still win out over injection for top end performance.
It really comes down to what you favor more of. Ultimate street riding throttle response or all about brute power. Most people want both...
and rarely achive it.... 
Throw a semi serious cam into the equation and sometimes CV carbs can be a real treat to get dialed in for good street behavior. To me, they're just not worth the time, effort and money when really good performance carbs are available.
They are a band-aid approach to performance that the factory needed in order to meet emissions and improve performance on stock machines.
The cross sectional are of a CV carb at the throat is one thing. You also have to take into consideration the throttle rod and the throttle plate. Both are flow killers. As such, you need the carb larger than a mechanical slide arrangement.
If I was going to do something serious and had to use CV carbs, the throttle rod would get halved and thinner throttle plates installed to improve flow. Same as the bored fuel injection throttle bodies.
The key thing with mechanical slide carbs is to not go too large. Get the right size on the motor and it's a pure joy to ride. Go too big with them and it's all up to the rider matching the throttle position to the rpm the motor is at.
A 1075cc street motor where midrange is primary focus will work very well with 31mm CRS carbs. For a 1015 or 903 street motor [same criteria] 29's. When you get to 1200cc, then jump to CRS33's or RS34.
Electronic Fuel Injection is all about throttle response. Fuel injection is no guarantee of improved HP. Often in certain classes of racing, carburetors still win out over injection for top end performance.
It really comes down to what you favor more of. Ultimate street riding throttle response or all about brute power. Most people want both...
and rarely achive it.... Please Log in or Create an account to join the conversation.