Summary
About a month ago I made it though the entire very long SmartCarb thread over at KTMTalk. After doing so and speaking with the guys at SC I wrote this summary so if someone didn't want to wade all the way through they could get answers to the basic questions. I had at that point also made it through about 1/3 of this thread, mostly the last third.
I pre-ordered a 38mm cast carb and until they come out I'm not sure what else there is to talk about so I haven't kept up. So sorry if this stuff is old hat but I thought it might be helpful and should cross over to GG.
>>>I'll summarize as I see it so someone not wanting to spend the considerable time to read the whole thread will have some basic info in one post.
Die cast carbs will be about a pound lighter then the billet.
The billet carbs are 300grams heavier than a stock carb. I don't know if I read that here or in the GG thread but the die cast may actually be lighter than our stock Keihins. Whom ever said 300g is 6.5 oz, it is not. Ha.
They will also apparently have internal routing eliminating the external plastic tubes.
They will be around $400 or about half the price of the billet.
They probably won't be available until spring or maybe even summer, even though they hope for and say earlier.
The tapered carbs (36/38) are apparently designed for consistent WOT applications like snowmobiles or perhaps MX, but the straight bore are more what we are interested in, even for MX imo.
SmartCarb says that a 38 will be better on top end and give up some bottom and the 36 will be better on bottom and give up some top. But they also say a 36 is good for a 200cc and for a 300cc. The GG guys are mostly all running 38mm SmartCarbs on their 300s. I think because most of their 300s came with 38s from the factory and a few came with 36s. They report good throttle response from off idle to WFO with 38. So a 36 or a 38 for a modded KTM 300SX is still a bit unclear to me. [[I went with the 38. Not that I had a choice at this point]]
The biggest issue to date is the lack of an overflow tube which allows for filling of the cylinder with fuel. This seems to happen somewhat regularly during installation (stuck float I think) or if the bike is inverted, or probably even laid down on it's side considering how quickly fuel runs out when I lay my bike down. Some report considerable trouble getting the fuel out once this has happened. The die cast carbs will likely have external overflow and they are working on a retrofit for the billet that they will provide to anyone who has already purchased a carb; at no charge as I understand it. <<<
SC also said that they would be sold with a throttle cable included but had yet to find a vendor to supply at a reasonable price. I think I read here that they have worked out the stock cable issues but have not verified that. Maybe that is more of a KTM problem.