Rebuild of a Solex carburettor 26AIC

I am always keen to rework old mechanical parts, not only to satisfy my thirst for knowledge but also for the pleasure to bring back to life an old thing long forgotten.

In this article, we will review a Solex carburettor 26AIC.
Here is the thing:

I have been happy to discover that mobile parts were not seized :D

A bit of history:

This carburettor was initially fitted on Renault Juvaquatre (1938-39):

Photo from Lars-Göran Lindgren (Sweden)/ Wikipedia

Another variant exists for Peugeot 202, with a slight difference however: on the top, the 26AIC for the Peugeot has two holes to attach a protector on top:

The Solex 26AIC has also been used on this models:

• Standard Flying Eight Side Valve 1938-48
• Reliant 3 Wheeler Regal 1952-58
• Reliant Export 1952-62

And also on industrial engines:

• Coventry Climax FSM2 & FSM3 Engines 1939-49

That's all for the history bit for now, the next step is to strip it down! 😄

Stripping down the carburettor:

Nothing special there.

Advice: take lots of pictures, to be sure that you will put back all components in the correct place and order ;)

Step by step:

1. Remove the small part hold by two funny screws/ 6 sided bolts hybrids on top of the carburettor: it is the fuel filter unit. Under this cover are (in order) a seal, a brass spring and a brass strainer. The screws have also grower washers (M6).
2. The nozzle where the fuel hose connects is missing together with its seal.
3. Remove the carburettor cover by taking out 3 squared screws/ bolts. 2 are next to the fuel filter unit, the last one is on the other side of the carburettor, with the head upside down (missing on my unit). Screws have M6 grower washers (one was also missing on my unit).
4. Under the carburettor top cover is the 1.5mm needle and seat assembly. A brass washer completes the assembly.
5. There is no seal between the carburettor cover and the main tank. That's surprising however that seems normal (not on the exploded view of a similar unit):
   
   
6. In the main tank seats a 11 grams float made of brass.
7. On the other side is a 26-19 venturi, that can't be easily removed from the shell. Usually, it does not need to be removed anyway.
8. Finally, close to the venturi, there is a small jet, the idling jet air bleed:
   
   
   
   
   
9. On this face of the carburettor, the big bolt contains the main jet assembly. The jet itself is a 100 calibrated one, screwed in a jet carrier that also carries on a seal:
   
   
10. The other item visible on this face is the mixture adjusting screw, made of brass, together with a steel spring:
    
    
    
    
    
11. On this face from left to right and top to bottom:
12. The idling jet, ref 345. Its use is to adjust mixture at idle and just off idle. Once off idle, the main jet takes the lead.
13. The screw on top right is... just a screw. Nothing hidden behind!
14. Under the screw lies a hole. There should be the starter jet that is missing on this unit. This should be a 110 calibrated jet.
15. And finally, the bottom part is the mechanism linked to the throttle assembly (refer to point nb 20)
16. The assembly on the right side is the automatic starter mechanism:
    
    
    
    The starter assembly is attached to the carburettor shell with 4 brass screws. Once removed:
    
17. The part at the bottom is use to attach the starter cable housing. It is hold by 2 screws to the starter mechanism. BE CAREFUL it also holds in place the spring and ball from the starter mechanism:
    
    
18. On the side of the starter mechanism seats a 4mm air intake (brass screw ref. AIR-4)
19. The assembly on the front is composed of the components as shown on the next picture. The mobile part that receives the extremity of the cable starter is crimped to the lever, and not with a retaining ring like for other models. Could be source of trouble if heavily corroded
    
    
20. At the bottom of the carburettor can be found the throttle mechanism:
    
    
    
    
21. The bolt and screw on the left of the second picture receive the accelerator cable.
22. 2 screws assemblies are visible: the one on the left of the second picture, composed of a screw equipped with a locking nut is there to set the maximum opening of the throttle (basically, the throttle plate should be aligned with the venturi axis like on the first picture). The second screw assembly, the one with a spring, is the slow running adjustment screw.
23. The nut holding the throttle lever can be easily removed, together with the lever and the abutment plate under.
24. The throttle plate is attached to the throttle spindle with 2 screws. All parts there are made of brass.
25. The throttle spindle can be removed from the carburettor body once everything else has been removed. This unit is quite basic: on later models some spindle seals are fitted.
26. And, once you have removed this last component... You should have an empty body in hand, meaning the carburettor has been taken apart!

Cleaning the components:

Once everything has been taken apart comes the cleaning phase.
This operation can be performed using different methods and tools, pending of the equipment available to you and pending of the result you want to achieve.
For example: ultrasonic cleaning, soda blaster, etc.
Lots of videos are available on the Internet if you want to have a look.

Notes:

• If you were to use chemicals (whatever they are), do not mix metals: keep them separated to avoid any accidental red-ox reaction (you do not want to get dark marks on your brass parts or discoloration of the carburettor body...)
• Be careful not to use hard brush or other abrasives, you would end with scratched parts that could affect not only the cosmetic aspect of the carburettor but also the functional functions (loss of tightness around the sealing planes, etc).

No blaster available here at the time, so I have used more basic means: gunk dissolver, detergent and a soft/ medium brush.
Ok, so basically:

• I have left the parts in jars full of gunk dissolver for around a week,
• Wiped the components, rinsed them with (very) hot water,
• Clean the parts with detergent and using the soft/ medium brush,
• Dry the components and wipe them thoroughly using a polishing cloth or similar.

That should give you good results.In my case, I didn't want to get the carburettor "shiny as new".  It is more than 75 years old and has an history, previous lives and therefore I wanted the part cleaned, free from damaging corrosion but with its patina :)

Reassembly and conclusion:

I will not go in details to explain how to reassemble the components together: just reverse the steps described in the "Stripping down the carburettor:" section, and using the pictures you would have taken ;)
Normally, no greasing required, except a very little quantity of grease I usually add to the little spring that goes with the little metallic marble that fits inside the starter mechanism.
Here is the result:

   

In the end, the carburettor is not fully ready, as some parts are missing:

• 1 screw that attaches the carburettor top to the main body,
• 2 grower washers for the screws that attach the carburettor top to the main body,
• The starter jet (should be GS 110),
• 1 seal for the starter jet, dimensions 
• 1 nozzle to connect the fuel hose,
• 1 seal for the fuel intake nozzle.

Updates:

- 04/02/1018: Found the starter jet
- 23/02/2018: Found the grower washers and screws for the top of the carburettor

More updates to come! :D