Practically Classics Forum

I think i know the answer to my own question but could do with some reasurrance!

spitfire 1500 was running very rich so i bought a gunson colourtune and even on full adjustment was still showing as running rich!

the leaflet says a worn carb needle/s (correct?)

question is do i need to also change the needle guides?

the issue manifested itself in sooty plugs but also a severe hesitance under load ie 4th gear up an incline, rekon this is down to the wrong mix or possibly a timing issue?

cheers guys
joe

I'd say yes. The needles wear by rubbing on something, which is the jet/guide. The needles will wear over the whole of their travel (although mostly they will wear at the point that they spend most of their time, about 1/4 to 1/3 open) but the needle jet/guide will wear in the same spot all the time, so if anything I'd say the guide will wear even more than the needle in terms of how it wil affect mixture.

These are not hugely expensive items, so if you want to get it running spot on and there's any question of wear, then yes, replace both (in both carbs of course) and you have a great starting point for final adjustment and tuning.

Unless they are just the wrong needles to start with of course...

IMHO of course.

yes sounds like a good plan!

i tried to use the colourtune and just could not get a blue colour so indicating worn needles!

ill get some new ones and see if i have any better luck!

cheers