modifying carb for mixture screw.

[tooljunkie]

so has anybody modified a carb to adjust the mixture without resizing the main jet?
i have noticed my bike likes cooler weather like in the morning,and isnt so happy in the afternoon.
so i was thinking of introducing an air screw somewhere,even in the intake.
i'm aware that i could cause issues as far as leaning it out too much and burning it up,but i think leaning this one out enough to minimize four-stroking without a smaller jet would make it a little nicer to drive.

i'm jetted about four number drill sizes smaller than stock in my stock nt carb.
was thinking about the nt speed carb gen2 or the cns,but i have read so many mixed opinions.

your thoughts are appreciated.

 

[Pilotgeek]

I wish my NT had a mix screw. I had to jet it for a compromise as well. It runs great in the 70's, runs just a bit lean in the 50's and 60's, and a little rich in the 80's and 90's (temperatures, I don't have some crazy time-travel bike. Wouldn't that be neat, though?). I deal with it, because running a little rich when hot out helps keep the engine cool, and I can afford to run a little leaner/hotter when it's cold out. I know a few people have bought high quality carburetors not intended for these kits, such as a 14mm Mikuni or Dellorto.

 

[crmachineman]

Carbs.....

Hmm, it sure can be confusing.....

I have worked with the CNS carb. for a while, fiddling and fiddling! Then, after the second CNS carburetor body broke at the clamp, I decided to no longer struggle with the CNS carb.

I put the little NT "speed" carb. on as an emergency measure. The bike runs great! faster than ever; wow, I guess they weren't kidding when they called it a "speed" carburetor!

Now, I'm trying a carb. from DAX. I think it's a Dellorto clone which uses an interesting flat slide. It is a pretty nice, simple design. The flat slide does not have a fuel metering needle attached to it. As the slide opens up, it exposes the progressively drilled fuel delivery tube to the air steam. I found very good smooth and seamless engine performance with this carburetor, great idle too, however, based on my experience, it doesn't seem to produce as much power. The only reason for this that I can muster is that this design is slightly more restricted, because the fuel delivery tube, which is fixed right in the middle of the air stream is larger in diameter as compared to a round slide with a solid needle.

I hear the Mikuni carbs. are nice. I would like to try one.

-Fred

 

[Pilotgeek]

The Mikunis are quite expensive, though. I would have tried one already otherwise.

 

[crmachineman]

Yeah, me too!
-Fred

 

[tooljunkie]

there's a product made for mikuni carbs,dial-a-jet.
it works using vacum if i understand it correctly.
used on snowmobiles primarily,the control is on the handlebar
and adjustment compensates for three or four jet sizes.
was considering an adjustable vacum leak,but i could be
setting myself up for catastrophic failure.

 

[Pilotgeek]

Hm, I just looked up more about dial-a-jet. It seems like a second jet that you install, that automatically compensates for a lean mixture. You set your main jet just slightly lean, and the dial-a-jet add to it. I wonder how it works. If a system could be duplicated for our tiny carburetors, that may be the answer.