running rich

[martin418]

hi my s2 has a 1098 engine and matching carb fitted , it starts and revs up perfectly but is running rich at idle and the jet is screwed up as far as it will go ,it has the correct needle and jet all set up to the book , the needle looks perfect , am i right in guessing its a worn jet , i am ok on webers etc but su's are no my strong point !

[philthehill]

Could be that the fuel level is too high in the float chamber and yes it could be a worn jet and even a worn needle.
See http://sucarb.co.uk/technical/ for all the technical information you will require to tune and adjust your SU carb.

The SU carb is a doddle compared to the Weber. Got a pair of 45DCOE13s fitted to my Minor.

[martin418]

good thinking fuel level or needle not seating , i will disconect the fuel pump and manually fill the float bowl and see what it runs like

[bmcecosse]

Rich at idle is indeed usually a flooding float chamber - when running at decent revs it uses the fuel so appears normal.

[martin418]

the float chamber fuel level sit's just above half , i think it might be a weeping needle valve as there is signs of fuel weep around the float chamber top cover when running so i am going to disconnect the fuel pump when it's idling a see what happens

[martin418]

no difference i suspect it's a worn jet

[philthehill]

Don't just replace the jet - replace the needle as well. The needle may not look worn but if the jet is worn the needle will be worn. Pity to spoil the ship for halfpennyworth of tar or in this case £8
You might as well replace the float chamber needle valve whilst you are at it; because as you say there is some fuel weep-age around the top of the float chamber.

[martin418]

hi i will fit a rebuild kit to be safe