13 replies to this topic

[jpw1275]

hi.... what is the difference between the red and black jets?

cheers james

[lrostoke]

This is just a guess but if you google image hs6 jet they mostly come up black

hs4 jet come up red

 

so I'd say black are larger for the 1.75" carbs

red are for the 1.5" carbs

[jpw1275]

ah ok.... only asking as ive got 2 sets of twin hs2 carbs... one has black jets and the other has red jets

cheers james

[lrostoke]

wont be size then :)

 

probably just different plastic

[dklawson]

I am not sure that the color indicates carb size.  A lot of the early small bore Triumphs used jets with the red plastic elbows on them while all the BMC products I have worked on seem to have black elbows.

 

Regardless, if in doubt, measure the bore of the brass tube.  There are indeed different sizes, 0.090" and 0.100" holes.

[jpw1275]

So am I right in thinking that the bigger size would be classed as an upgrade?

Cheers james

[dklawson]

No.  The bigger hole in the jet has to be used with bigger diameter needles.  

 

It's not so much an upgrade as components that have to work in matched sizes.  Remember that SU carbs were used on a tremendous number of make and models of cars, many with much larger engines than the Mini and therefore, greater fuel demands.

[jpw1275]

Ah ok cheers for that dk

James

[carbon]

Black plastic jets = semi-down-draught

 

Red plastic jets = horizontal

 

Available in both 0.090 and 0.100 jet sizes (at least that's what the SU reference manual says, exactly what the difference between the red and black jets is I am not sure, they look very similar).

[Dan]

  The difference is the hose is slightly longer to allow for the different float chamber angle.  If the carbs are horizontal the bottom of the float chamber is closer to the jet, as it angles up and you change the float angle adapter the distance between them increases.

[carbon]

Thanks Dan, that makes a lot of sense

[jpw1275]

cheers for that dan.... so im guessing black are for 30 degree say and red for 20 degree and under where the float bowl is further away

cheers james

[carbon]

Red jets should be used for either horizontal or up to about 10 degrees downdraft.

 

Black jets for about 20 to 30 degree downdraft.

[jpw1275]

Ah cool.... That's my question answered then...... Cheers guys