Spring loaded needle???

[afterburn2727]

Hi, I was looking at the selection of needles for SU carburetors (HS6 specifically), and I was wondering what the difference is between the spring loaded needles and the fixed needles. Where is the spring located? Thanks for the help.

-Matt

 

[sammyb]

The spring is located in the piston behind the needle. Look at your current needle...a non spring loaded one is just a little thicker as it goes into the piston. A spring loaded needle actually has a shield around it. If the cylinder directly around the needle where it mounts to the piston is the same color as the needle, it's probably spring loaded.

Easiest thing is simply to unscrew your dashpot, pull the piston out, and loosen the needle retaining screw on the side of the piston and CAREFULLY pull the needle out.

 

[afterburn2727]

Thanks a bunch.

I recently obtained a pair of hitachi/SU's (basically SU HS6's with subtle differences) and planned on mounting them in my TR6. I read from a few sources that the true SU HS6's had spring loaded needles, but it seems that my carbs have the fixed type. Someone also told me that the needles would be interchangeable, which they are not... I had never worked with the spring loaded variety, so I just wanted to verify with someone with more knowledge.

Again, thanks for clearing things up.

 

[piman]

Hello AB2727,
the spring loaded (biased) needle was a later "improvement", like the wax stat jet which compensated for temperature to adjust the mixture.
I thought that the needles were interchangeable and certainly the biased needle does wear more and also wears the jet as it constantly touches it. I would prefer a fixed over the biased any day. It is not really difficult to make up a sleeve, if necessary, to fit the fixed needle.

Alec