Carb tuning.

[SaintGeorge]

Hi all, i recently rebuilt the Strombergs, including main jets,needle valves etc. Been trying to tune them and they are not too bad but not perfect. Ive noticed that on adjusting the mixture one of the mixture screws has gone fully to the rich side or clockwise side and wont go any more, so is at its limit but could probably do with a tiny bit more ! any ideas would be appreciated.

[trunt]

Which needles do you have? The B1AQ is slightly leaner at idle settings than the B1BF, otherwise they are basically the same. I tried both and had exactly that, just about right but at the rich limit of adjustment. The B1BF brought it into range.

If one carb is significantly different than the other it may be worth investigating, eg sure they are both the same needles? Plus of course float heights, jet height, compensator etc.. all can affect the idle.

Terry

[SaintGeorge]

Cheers Terry, i will have to check the needles,but thanks for helping.

[sujitroy]

I reset the needle heights to max lean and on initial runs, the car drives smoothly. I have been told with modern fuels you really can't tell the correct mixture by plug colors as in the older days. I have have not driven the car much as I was on vacation

[MikeParker]

You say you have changed the jets also. The height of these also affects the mixture, so worth checking they are not too high. They should be 2.1 to 2.7 mm below the bridge. That measurement is to the land around the jet orifice. Also check that the needle really is being pulled up into the piston. It may have come off the bottom of the thread and so not being pulled up. At its most rich, it should be a couple of mm up inside the piston.

Mike

[MandM]

Recheck the float heights, this can affect the mixture, if yours are slightly to large this will make the mixture weaker as the fuel will be lower in the jet, this is what I found on mine (18mm) as it always seemed a bit lean, at the MOT, check the other stuff as well but this might be just the bit you are looking for. or I could be wrong and stand corrected.