Spring loaded carb slide needle

On my XJ650 Seca carbs, there is a small post inside the slide where the needle seats that causes the needle to spring bias towards the rear. Any idea why the needle on the carb slide on the xj650 is spring loaded like that? Also, is it normal that these needles are aluminum or is it possible that this is a replacement part like from Factory or some other carb tuning kit? All my other bike's have a SS needle.

 

I never noticed that the needles are aluminum, but it wouldnt suprise me.

These are Constant Velocity carbs that use a vacuum to raise the diaphragm. The spring is an assist to get the slides back down. They will still kinda work when you remove the springs, but the springback wont be as good and the slides usually don't return to their homes. Even with the springs on, if you turn your carbs upside down, with the spring and the vaccuum, the slides still have trouble fighting gravity, and will only return 1/2 way.

These carbs are finicky, and I would be willing to bet that if the jets are original, there is no shim on the needle itself, or the mixture screw aluminum plugs are still there, that your bike is stock.


-Kaya

 

Hi, no not the main slide return spring, but the small spring that is between the plastic hex retaining cap and actual needle. Yeah, these needles seem to be biased via spring pressure towards to the 'front of the bike', not straight on center with the carb slide. Also, the needles can be pressed in towards the slide by about .150" or so. Just seems like a curious details.

Is there supposed to be some sort of shim on the needle? Do you mean that someone may have added a washer to raise the needle height? None in mine. 'I' did however pull the mixture screw plugs and screwed out the mixture screws to ensure all was junk free within.

 

all the needles are aluminum, the little spring keeps the needle at the bottom of the slide but still lets it spin around. did you see a little pin down in these?, that's what kicks the needle to front, with the spring pressure it helps the needle from rattling around
washers or shims are put in by guys trying to tune the mid-range richer,
they are not original parts