Following on from various fuel ,timing, valve setting threads,what is the general concensus on primary jet size , is standard 102 so go up to 105 ? Also if i knew someone who didnt know where on the carb it is ,where would i tell him to look by way of a handy photo perhaps (don't have a carb in front of me at the moment )

I've got an 86 engine in my van with i assume standard compression , i fitted a 123 and set the valve clearances to 0.2 and 0.25 and use b7hs plugs and it runs well enough with the plugs colours ok ,i do use 97-98 when driving it hard as in long journeys with foot down but yes it runs ok on ordinary 95 although i do avoid E10 if labelled as it is in France.

But i've never looked in any depth at the carb on this one tbh ,didn't need to on my previous 2cv although my old AKS i tried to mess about with its single choke carb a bit.

It's the oval venturi twin choke type on this one, i assume standard on post 82-ish engines ,26/35? What is the 18/26 and 21/24 business referring to when looking at the jet page on ecas,i.e are there two types of 26/35 that would require different jetting ?

107 guessing that as you have a flat spot you have a 18/26.

26/35 is the solex number prefixed with PCIS or the like. 18/26 or 21/24 refers to the choke sizes in the carb(they are cast into the side in little circles-theres no point in peering down the barrel as they all have the same tops and youve nothing to referace it against) the 18/26 being the more common as fitted from the early 80s as they tried to lean out the engine in response to increasing emissions paranoia.

21/24 is the gas guzzler of the 2cv world

coffee brake over wheel and tyre changing time

Ok cheers just had a quick look its the 18/26 ,will have a look at the primary jet later.
It hasn't got a noticeable flat spot as such ,at least very rarely anyway but i want to check it over after having read a few pieces on here about upjetting the primary i realised i haven't even looked at the carb and wouldn't know if the previous owner did since the van had only been 'recommissioned' after a good few years off the road a few months before i bought it.

ben,
don't make the mistake which some folk have made, which is to confuse which is the primary petrol jet and which is the secondary.

Just had an email this morning from a fellow in Florida who's drilled out the secondary from 90 to 107.5.

Pic here, also showing the secondary butterfly stop screw which should be backed off by about 1/2 to 1 turn if the carb's done a good mileage.

http://www.flickr.com/photos/30132857@N06/

ken

Thanks Ken- are the jets marked with their size as i would expect?

Ben,
yes, they are. It's worth checking them if there's any question about the mixture.

Wasn't it Neil's/Alkie's Acadiane which had the a primary petrol jet from a 21-24 carb fitted to an 18-26 version, which would have been far too rich on the first choke.

ken

Well its a 102 and the other a 90 so all standard. The top screws weren't that tight and the bowls had a fair amount of crap in them (i did fit a filter down below when i got it) ,fairly surprised how well its behaved considering.
Bit dizzy from carb cleaner spray inhalation now
Have backed off that screw by half a turn from where it was and going to change main to 107.

First time its ever done this ... went to start it this morning, foot flat to the floor and the pedal stayed there ,the throttle linkage felt as if it had gone 'over a threshold' ,and flipped back ok by hand .
Throttle return springs are fine, i put a new one on last year and left the old one in place.

Behaved on the way to work think i've just probably dried out the linkage a bit with carb cleaner spray

they can go "over centre" if it happens again move the return spring to the end of the yoke pin rather than out on the end of the bracket

After fitting some new headlining a few days ago, went out for a spin and while out had a curious stuttering or kangarooing when the throttle was about half way down. Imagine 30 mph in third, about that level the engine was misfiring and a bit rough.

So getting back to the garage, and remembering this thread and the similar ones recently, I took a look in the carb as the symptoms seemed like the carburettor may be the problem. (pretty much everything ingnitiony is new or recently changed, plugs look good)

This was on Saturday when the temp was about 28 according to the temp gauge in the other car. 2cv has never done this before, wondered if the temperature has an effect...

Having a look after taking the top off the carb. It looked like there was stuff at the bottom, but really there was only the merest smear of stuff, the in line filter had been working. What you can see here is mostly some kind of discolouration of the bowls.



Cleaned inside as best as I could, but never having cleaned the jets before didn't really have any idea what or where they are, so tried looking for something more obvious, then found:



The tiny spring which holds the choke flap axle against the other choke axle had broken, you can see it hanging down in the centre of the picture.

Triumphant I was sure that I'd discovered the cause, so put the carb back together and bent a new part of the spring to re-intstate it until I can get a new one. Test drive and nope, no difference still kangarooing in the mid range of the accelerator, particularly when revs are dropping into that range down from higher revs / more throttle.

Left it for the day and came back here to read about carbs and jets. Symptoms seemed to match a blocked primary jet, so next day went out and removed the jet while the carb was in situ. Never could have found it without Ken's photo, Haynes was pretty hopeless in this respect.

Ken's photo much better!

http://www.flickr.com/photos/30132857@N ... otostream/
So its down there! I'd always expected the "Jet" to be the part sitting in the middle of the venturi (hole), or one of those brass things at the top of the carb.

What its actually doing is metering the flow of petrol into the engine simply by a precisely sized hole, have I got that right? When on full throttle with both halves open, you have 102 plus 90 flow maximum going into the engine. When you are runnning only on the first part of the carb / pedal travel, you have only 102's worth of petrol flow to play with?

This is the little fella: a 102 jet

Seemed perfectly clean when I got it out of the carb, blew it through and cleaned out the vertical pipe it sits at the bottom of as well as I could. used a cotton bud and flushed the tube through several times.

The carb is a 18/26 as it says on the side:

(or 26/18 )

Once all back together the engine was fine again, although that was the next morning which was much cooler (if temp is a factor?). Should I upgrade to a 107 primary in the light of this escapade? Was it just grit which I managed to remove in my cleaning? What do you think?

Sean you said

Is the 18/26 particularly prone to this more than the other carbs because its naturally 'leaner' than the earlier models?