The Triumph 2000 / 2500 / 2·5 Register Forum

I was rebuilding the carbs on my Mk1 Estate, and noticed that they had 6Q needles in them, rather than the 6J that every source I can find specifies. Could anyone enlighten me on the difference between 6Q and 6J, and whether there would be any reason to use the 6Q rather than the recommended needle on an unmodified car?

What I read in "Tuning Zenith-Stromberg carburetters" by Martyn B. Watkins (Speedsport Motobooks 1973) is that the 6Q needle was typically used in the Hillman Hunter 1725 (Iron head) and the Hillman Minx 1500..

These are the measured differences:

6Q 6J
.0885 .0880
.0846 .0841
.0815 .0799
.0789 .0777
.0764 .0748
.0726 .0721
.0685 .0693
.0649 .0662
.0615 .0628
.0582 .0590
.0582 .0555
.0575 .0514
.0575 .0500

Now somebody told me once that the Triumph 2000 tends to run a bit too rich when idling and in low revs while running too poor at higher revs.
It seems that the 6Q needle is solving this problem a little bit.. (IF it is true what I have been told).

Thanks a lot! Interestingly enough, the reason I set about the carb rebuild in the first place was the fact that it was running rich at idle, but far too lean at speed. The needles were visibly worn, though, and a fresh pair of 6J needles, and replacement throttle shafts, have made a night-and-day difference to its performance.

I can imagine. I did the same with my carbs about four years ago (though throttle shafts were good, I didn't replace them).
Still a little bit rich in lower revs though.

It's surprising the difference a new needle and jet will make. When I rebuilt my S , lots of black smoke which I couldn't adjust out. While they looked ok new bits fixed it.
Tony.