How do I adjust mixture?

I'm pretty sure my 2.25 petrol SIII is running too rich as there is a bit of black smoke from the exhaust and dry sooty deposits on my plugs. My question is to reduce the fuel in the mixture I assume I change the float level in the chamber, Haynes say from the base of the emulsion block to the top of the float should be 33mm, if I want a leaner mixture should I increase this distance by bending the tab or reduce it?

Any ideas, or should I be trying something else too?

Thanks

Tonners said:

I'm pretty sure my 2.25 petrol SIII is running too rich as there is a bit of black smoke from the exhaust and dry sooty deposits on my plugs. My question is to reduce the fuel in the mixture I assume I change the float level in the chamber, Haynes say from the base of the emulsion block to the top of the float should be 33mm, if I want a leaner mixture should I increase this distance by bending the tab or reduce it?

Any ideas, or should I be trying something else too?

Thanks

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What type of carb is it, most have fixed jets so I don't think you can adjust them that way, there is a standard height for the float, and of course the mixture screw only adjusts the idle mixture.

The SU and the stromberg are, you can move the jet up and down and the other move the needle. Probably the jet is worn.

If its a zenith carb, aint the mixture screws protected or "tamper proof"? looks like mines had the carb off and been attacked with a hack saw! Cant adjust mine

Does any one know how to convert to E85 and how to control that mixture, if possible?
Al Kaumeyer

on the zenith carb is the mixture screw not the bronze nurlled one at the base of the carb, pointing towards the cooling fan??

Its a zenith carb, I had a refurb kit from Paddocks a few months back so all the jets are new, volume screw is adjustable but only affects idle mix I think.

Tonners said:

Its a zenith carb, I had a refurb kit from Paddocks a few months back so all the jets are new, volume screw is adjustable but only affects idle mix I think.

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Thats what I think as well, once it comes off idle it goes onto main which dont have adjustment.

There would be a number on the jet, I hope it matched, the only other thing I remember causing rich mixture was it drawing air through the throttle spindle. But it's been so long since I worked on something like that I'm a bit out of tune.

Look down the carb and make sure it's not dribbling fuel in from either the idle jet or the accelerator pump, you will have to look very carefully since it only needs a whiff to make the mixture rich. Short of the main jet being too large that's all I can think of at the minute.

I dont remember ever adjusting the float level for mixture issues, normally the only time I would go there is if the float had burst, or the needle valve had stuck, both of course flooding the carb.

What was the original problem with the carb?

i think it does have an adjuster, the idle screw is under the throttle linkadge, but the mixture adjuster is underneath the main body on the engine side, and "needs a special tool" to get to

stupid carb, why do yah think i'm just gonna get a weber when funds are right?

david451 said:

There would be a number on the jet, I hope it matched, the only other thing I remember causing rich mixture was it drawing air through the throttle spindle. But it's been so long since I worked on something like that I'm a bit out of tune.

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can yer explain how drawing air through the spindle gives yer a rich mixture?

its easy, Slob - surprised yu dint know - the more air yu pull into the carb, the less petrol yu use and therefore the richer yu remain.

slob said:

can yer explain how drawing air through the spindle gives yer a rich mixture?

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From what I can remember it was causing the idle jet to continue to spill fuel into the carb, that's why I said to check that this was not happening or that the acc pump was still spilling probably because the diaphram was gone.

Infact it might have been the progression jet which you know is only a series of holes drilled into the body but it was ages ago and I cant even remember what kind of carb it was, zenith, solex. dunt know.

Mr Daft, even though you answer wur refering to the driver and not the fuel mixture it still sounds more plausable than wot him up there ^ sez

Thanks for your ideas, the original problem was that when running at a constant speed between about 30-40mph it would not run smoothly, it kept "missing" but ran fine on acceleration. Having raised the float height this appears to have all but solved that problem which was getting really annoying but now I have abit more black smoke and think its running too rich still.

I'll check the number on the main jet, didnt know there was one!

slob said:

Mr Daft, even though you answer wur refering to the driver and not the fuel mixture it still sounds more plausable than wot him up there ^ sez

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I'm goin off you again.

david451 said:

I'm goin off you again.

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aw! dint say that! yule get me all upset

slob said:

aw! dint say that! yule get me all upset

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You didnt say that wif sincerity, un I think the world of yer aswel, kind, loving, always a good wurd fur somfooker.

Ah well maybe yer havin a bad day, so a forgiv yer.

On the other hand I woz kindof hopin that guy "the deer huntur" drilled yer wif his winchustoor tho.