5 replies to this topic

[cristiano1968]

Hello
Anyone can explain the difference between blue red and yellow spring
Which will make the mixture leaner?

[cal844]

Mixture is controlled by the screw and needle

[nicklouse]

Hello
Anyone can explain the difference between blue red and yellow spring
Which will make the mixture leaner?

 

they are different rates to control the motion of the piston. (closest explanation is accelerator pump action)

 

http://sucarb.co.uk/...q=piston spring

 

 

and see above about mixture.

[hhhh]

The purpose of the spring is to control the piston such that it responds correctly to the pressure differential across the carb throat. At maximum engine torque, the piston should be at the top of its travel, but not before. Too weak a spring turns the carb into a fixed jet carb once it hits the top which would likely lean the mixture too much. Too strong a spring and it's like a too small carb is fitted.

Edited by hhhh, 09 March 2017 - 06:18 PM.

[carbon]

Good evening Cristiano,

 

Blue springs are weakest rate, red medium rate, and yellow stronger rate (green is even stronger). If you're using red springs be aware that the new red springs currently available can be a much higher rate than older red springs (this is for old style dashpots, not later ball bearing type which use a much larger diameter spring).

 

As well as needle and jet height the spring also affects the mixture strength.

- change from red to blue will weaken the mixture

- change from red to yellow will richen the mixture

 

If you change the spring rate you typically also need to readjust the jet height. For instance on going from red to blue you may need to drop jet slightly.

 

And you can also play tunes with the type of dashpot oil...

Edited by carbon, 09 March 2017 - 09:31 PM.

[cristiano1968]

Ok thanks for the good information everyone👍👍