I bought a Speed carb to replace my NT. I've got about a week under my belt using it so I thought you might be interested in my observations.
First off, a Speed carb looks almost exactly like a NT. About the only visible difference is, there's a built in petcock on the fuel inlet.
Closer inspection reveals the venturi's are different size in diameter.
NT carb........ = 13.74 mm
Speed carb... = 14.78 mm
Obviously the Speed carb is a little bigger.
So, to cut to the chase, does my bike go faster with the speed carb?
The answer is not really. It's seems to top out 38 mph with either carb. But there are other differences worth considering.
Such as, with all my 80 motors with a NT, they all seem to like to 4 stroke at partial throttle. The Speed runs much smoother at partial throttle. I'm running both carbs with the needles in the next to leanest setting. The NT was running a 60 jet, but the Speed likes a 64 best. The plug looks about the same now as either carb, which is a reddish brown.
It's hard to tell, but the throttle response might be slightly better with the NT at lower speeds. There's not much diff though. At higher speeds there's no difference that I can feel.
Starting is about the same either way. No choke, just work the throttle.
I think with a ported cylinder the Speed carb might offer a slight advantage powerwise, but with my stock cylinder I didn't gain any extra power.
So in conclusion, there's doesn't seem to be much difference in power, but the Speed carb cruises a lot smoother, with less 4 stroking. Just because of that I like it a little better than the beloved NT.
First off, a Speed carb looks almost exactly like a NT. About the only visible difference is, there's a built in petcock on the fuel inlet.
Closer inspection reveals the venturi's are different size in diameter.
NT carb........ = 13.74 mm
Speed carb... = 14.78 mm
Obviously the Speed carb is a little bigger.
So, to cut to the chase, does my bike go faster with the speed carb?
The answer is not really. It's seems to top out 38 mph with either carb. But there are other differences worth considering.
Such as, with all my 80 motors with a NT, they all seem to like to 4 stroke at partial throttle. The Speed runs much smoother at partial throttle. I'm running both carbs with the needles in the next to leanest setting. The NT was running a 60 jet, but the Speed likes a 64 best. The plug looks about the same now as either carb, which is a reddish brown.
It's hard to tell, but the throttle response might be slightly better with the NT at lower speeds. There's not much diff though. At higher speeds there's no difference that I can feel.
Starting is about the same either way. No choke, just work the throttle.
I think with a ported cylinder the Speed carb might offer a slight advantage powerwise, but with my stock cylinder I didn't gain any extra power.
So in conclusion, there's doesn't seem to be much difference in power, but the Speed carb cruises a lot smoother, with less 4 stroking. Just because of that I like it a little better than the beloved NT.
