CVT diaphram springs By twowheeler (Read 584 times)

[twowheeler]

Is there a rule of thumb regarding tension and performance? Does a more relaxed spring allow the slide to open faster and have better performance? Seems like all my carbs have different springs.

[Alleyoop]

I think your talking about the spring that puts tension on the cylinder slide that raises and lowers your main jet needle. That helps drop the needle down back into the main jet fuel outlet when you let go of the throttle. So if the spring is weak your rpms will drop slower when you let go of the throttle.
Alleyoop

[beebo]

You know, of all the tuning aspects of these little carbs, the diaphragm/spring is one I would not mess with. There is a delicate balance between the airflow/vacuum/enrichener rod/main jet that is tuneable with just changing the main jet, or if needed, the taper of the needle. That is really all you need to mess with for a fairly stock motor. If I felt it was absolutely necessary to fool with the spring, I would try to find a kit--let someone else with the proper resources and equipment figure out the best combo to use. Owning a Harley with a Keihin CV carb, I know there are kits out there for my bike--they include jets, needle, and spring that are matched for my specific bike. I don't know, however, of a similar kit for these little scooters. And I would consider the benefits gained for the cost involved. To me, spending 50 to 100 dollars for a 1hp gain would not be worth it. Just sayin'...

[Bashan]

Wow, I never thought about the slide spring tension being a factor. After some thought I wonder if it just has to maintain a minimum amount of force to keep it moving in the right direction and the vacuum, or lack there of, does the rest. Maybe that's why there's not "performance" slide springs. I really don't know. It seems like an imprecise entity. Rich

[cyborg]

Rich there's quite a bit of thought that goes into those springs ,,, it has to work with the barometric pressure , throttle position, inertia mass of the weight of the slide,,, whole heaps of calculations to figure the correct spring pressure and also it has to be very linear so you have even pressure throughout the stroke,,, even the little hole in the bottom of the slide itself is calculated

[cyborg]

Gimme a direct mechanical linkage anytime,,, I'm going thru the motions myself with this right now

[Alleyoop]

Every hear a motor rev quickly VROOM VROOM instead of VROOOOOOOOM VROOOOOOOOOM! Well old Carb Wizard here can make it do just that, OLD TRICK of the trade and it has to do with the slide but I only give that secret out to real hot rod guys
Alleyoop

[FACE PLANT FOR LIFE]

May 6, 2014 21:57:01 GMT -6 Alleyoop said:

Every hear a motor rev quickly VROOM VROOM instead of VROOOOOOOOM VROOOOOOOOOM! Well old Carb Wizard here can make it do just that, OLD TRICK of the trade and it has to do with the slide but I only give that secret out to real hot rod guys
Alleyoop

You've caught my interest!

[twowheeler]

Obviously a softer spring will allow a quicker lifting of the diaphram and probably result in a faster rpm increase ?

[FACE PLANT FOR LIFE]

May 7, 2014 7:57:01 GMT -6 twowheeler said:

Obviously a softer spring will allow a quicker lifting of the diaphram and probably result in a faster rpm increase ?

I would think we would be looking for a stiffer spring so that the RPM's drop quicker?

[cyborg]

For quicker response you drill a second hole in the bottom of the slide ( a small one) you can get the slide to jump up pretty quick,,, dyno jet made a fortune off of jets needles and a small drill bit,,,, and the difference is noticeable,,, but nothing like a flatslide carb with an accelerator pump,, I imagine the et will wheelie when and if I ever get the carb from sudco,,, ( wish they would hurry up alright already)

[Bashan]

Well obviously everyone missed my reverse vacuum thruster mod that lifts the slide 20% faster! Come on people! It's on the site....do I need to spoon feed you?!

[Alleyoop]

Now we are talking RICH
Alleyoop