tobyd
Member
It's on the engine side of the carb near the base. Awkward to see from the wing side.
If you look at the carb from the wing (6 o'clock) the mixture screw is 11 o'clock near the base.
Hope this helps.
Been trying to adjust mine today as was running rich. Now I think it's a touch lean as the exhaust is popping a little on over-run .
If you look at the carb from the wing (6 o'clock) the mixture screw is 11 o'clock near the base.
Hope this helps.
Been trying to adjust mine today as was running rich. Now I think it's a touch lean as the exhaust is popping a little on over-run .
kommer2013
Active Member
i had a zenith in my 2a, some had a black plastic shield protecting the screw from being turned easily, i would take mine off strip the whole thing down clean it put it back together, turn the mixture screw in as far as it would go without damaging anything and then turn it out 3 turns, then start from there adjusting lean or richer.
i ended up taking the zenith off and put a Holden Stromberg bxv carby on, it has the right jetting, and it sure made a big difference to the pick up and smooth running.
Tony.
i ended up taking the zenith off and put a Holden Stromberg bxv carby on, it has the right jetting, and it sure made a big difference to the pick up and smooth running.
Tony.
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ronsealdeath
Sagging Member
Na the mot man is using modern equipment for a modern motor. The 2.25 was always designed to run a bit rich. Exhaust pop is normal. I think I did a post on this ages ago but am on my phone so cant do a link. Try and search maybe. Ive forgotten what the procedure is.
Ive got the zenith 36iv service guide here too which is useful. I did try and attach it but its too big. Ill have a scan again on setting the mix
Ive got the zenith 36iv service guide here too which is useful. I did try and attach it but its too big. Ill have a scan again on setting the mix
TooMany2cvs
Active Member
I've just been going with this on mine today.
One little wrinkle made the mixture adjustment screw do absolutely nothing - and that was that, on removing the screw, the groove down it was COMPLETELY blocked with old varnishey muddy gunk.
MOT fail on mine was very low CO (~0.15%) and slightly too high HC (~1400ppm), which wasn't a surprise, since the lack of any kind of idle meant that I had to leave the choke on a whiff - but it ran beautifully.
The idle screw (throttle stop) wouldn't screw in enough to idle, so I've moved the locking collar to the back. Idle as low as it'll go without dying, and mix set 1.5 turns out, then out until it sounds nicer.
It's now idling and pulling reasonably smoothly, but has gained a bit of a "fluff" accelerating hard in third. It doesn't seem to start quite as easily as it did, either.
We'll see what it comes up to on the MOT machine, and what we can get it to.
One little wrinkle made the mixture adjustment screw do absolutely nothing - and that was that, on removing the screw, the groove down it was COMPLETELY blocked with old varnishey muddy gunk.
MOT fail on mine was very low CO (~0.15%) and slightly too high HC (~1400ppm), which wasn't a surprise, since the lack of any kind of idle meant that I had to leave the choke on a whiff - but it ran beautifully.
The idle screw (throttle stop) wouldn't screw in enough to idle, so I've moved the locking collar to the back. Idle as low as it'll go without dying, and mix set 1.5 turns out, then out until it sounds nicer.
It's now idling and pulling reasonably smoothly, but has gained a bit of a "fluff" accelerating hard in third. It doesn't seem to start quite as easily as it did, either.
We'll see what it comes up to on the MOT machine, and what we can get it to.
TooMany2cvs
Active Member
I'd really like to see that - I'm happy to put it on Dropbox or similar, if we can figure a way to get it to me.
ronsealdeath
Sagging Member
Will have a try later buddy
ronsealdeath
Sagging Member
OK, try this
https://drive.google.com/file/d/0BzmF8nvZr-z_R0ItQVlKR01iQ1k/view?usp=sharing
Should work and take you to the bulletin jobby. Good document and useful for me when rebuilding and troubleshooting my Zenith. It was so useful, I bought a Weber 34ich
https://drive.google.com/file/d/0BzmF8nvZr-z_R0ItQVlKR01iQ1k/view?usp=sharing
Should work and take you to the bulletin jobby. Good document and useful for me when rebuilding and troubleshooting my Zenith. It was so useful, I bought a Weber 34ich
TooMany2cvs
Active Member
That worked, ta.
