[Corey]

Phil, its all about the signal to the metering rod: The thing to remember is a caburetor is a passive device and can only respond as well as the engine it’s attached to; in terms of airflow and overall efficiencies. The shape of theSmatCarb’s venturi does an outstanding job of communicating mass airflow to the metering rod, insomuch that the caburetor becomes fairly indifferent to the metering rod (more specifically the size of the aperature at the needle/nozzle interface), and only shows problems if it is way too lean. I think Glenn stated earlier in this forum that what he thought it sounded like “is that you can go a lot richer and still have efficient atomization” and he is correct, you can run the carburetor very rich and still have decent performance. An interesting side note is conversely if the metering rod is too lean it simply won’t run hard enough past idle settings to hurt the engine, eliminating burned pistons. You don’t have any intermediate circuits to cheat it long enough to run through to the point of overheating the piston.

We do have different sizes and series of metering rods. Most changes are usually related to displacement of the engine only and have little to do with engine modifications. We typically use only one metering rod, from full mods to totally stock and have excellent results.

The ideal way to change the “preferred characteristics” with a SmartCarb is venturi size. For riders who like a milder hit with a lot of top end we recommend a 40mm for 250-300cc’s, for those who like a lot of torque and a little less top end a 36mm is recommended and for those who like both we offer a taper bore 40/38mm and 38/36mm.

Corey

2011 GasGas EC300