Thread: Replacing Seats/Jets in Solex 175 CD Carburettor

Are you talking needles and seats that regulate the fuel flow into the carby?
Or are you talking the mixture needles?
The mixture is determined by the needle entering the main jet, so you have to replace the needle and main jet.
The "seat' in the carb body is not that relevant. I had to change mine in Saudi to pass ADAC and I replaced the needle and main jet and it then was lean enough to pass.
The "needle and seat" for fuel is all screw in AFAIR.
Regards Philip A

Hi PhillipA,
Thank you for your reply. Sorry, my terms were vague. I refer to the mixture needle & main jet. Can the main jet be removed easily at home?
Many thanks,
Edward ☺

If the carby has a brass nut in the middle of the base , its just a matter of undoing it and the mainjet is attached.

The later carbys with an alloy "bump" on the bottom, have the main jet come out from the top, but AFAIR it is just a screw out operation. The later carbs have a self centring needle so should not wear the main jet (as much I guess)

Regards Philip A

You need a special tool to adjust the needle. I had one, but sold it with the carbies. You can get them off ebay for a few dollars. Can’t see why you would change the main, most metering except wot
is handled by the needle, it probably needs lowering a little to account for wear.

The main jet can also wear, particularly on the older carbs where the needle doesn't self centre.
Regards Philip A

Thanks Clive22 and PhilipA for your help.

Good to hear that the jets may screw out from the top (my carbies have the alloy 'bump'). I will investigate.

I have been lowering the needles over time, but they are now down as far as possible and it is still running too rich. Perhaps just replacing the needles would help a bit, but it also appears that the main jets are no longer round, but slightly oval. It looks like the needles have been rubbing on the jets as they have flattened edges on the needles.

Edward

I have a jet adjuster tool if you need to borrow it, and a Unisyn. Oh, and a Colortune.
There are two types of adjuster , one is like a blade screwdriver and one has a U at the top. Mine has the U.

Also if you are losing oil from the dashpots, there is an Oring under the needle holder, but the needle holder is a press fit and I was never game to remove it as if you scratch the inner bore of the needle tube the oring will not seal. I put up with the leak of oil.
Regards Philip A

Originally Posted by PhilipA

I have a jet adjuster tool if you need to borrow it, and a Unisyn. Oh, and a Colortune.
There are two types of adjuster , one is like a blade screwdriver and one has a U at the top. Mine has the U.

Also if you are losing oil from the dashpots, there is an Oring under the needle holder, but the needle holder is a press fit and I was never game to remove it as if you scratch the inner bore of the needle tube the oring will not seal. I put up with the leak of oil.
Regards Philip A

I much appreciate your kind offer PhilipA. I'm not sure what a 'jet adjuster tool' is though. I still can't work out how to remove the main jet let alone adjust it! Are you referring to the earlier carbies with the adjustable main jet? I have attached three photos (i hope!) of an old spare carb i found today that is identical to the carbies on the vehicle. I tried to drift the jet out with no luck, but i didn't try too hard because i don't know which direction to drift it.

Yes i do have leaky dashpots, but like yourself i just deal with it.

Edward