I recently discovered that 4194's Solex 35 accelerator pump was leaking fuel from the vent hole in the pump body. Upon further investigation, I verified that the accelerator pump diaphragm had dry rotted and split. Obviously, rotted rubber parts are not uncommon in a carburetor that is nearly 40 years old. In fact, I encountered a similar problem with the both of my single bbl Solex carbs. Thankfully, I was able to use a replacement VW accelerator pump to repair the single BBL carbs. However, in contrast to the single BBL Solex, the accelerator pump for the 2 bbl Solex 35 is 100% NLA worldwide. I tried a number of carb specialists in the US and EU to no avail. Even the Alpine specialists indicated that I was out of luck.
Yes, I'm jealous of those of you who are running Autolite carbs due to your ability finding parts on the shelf at the local Autozone! I was tempted to capitulate and scrap the Solex system, but rather than admit defeat due to a small piece of failed neoprene, I did some research and determined that I could replace the diaphragm. I ended up ordering 3 different diaphragm materials from McMaster. These included two variations of neoprene and one piece of viton.
I also ordered a used Solex 35 CEEI carb from a junk yard in Ohio, that way I had an extra accelerator pump to work with. (Ironically the accelerator pump on that carb was "okay" so I ended up transferring the pump to 4194 in the interim.)
The diaphragm material on the pump is sandwiched between two circular plates which are pressed to the accelerator pump shaft. To minimize the risk of damage, I invested in a drill press to drill out the pressed section.
After drilling out the pressed rivet, I disassembled the diaphragm and used the original as template to cut a new diaphragm.
I then very carefully drilled and tapped the diaphragm shaft to accept a M4 screw.
After that I put it back together.
After reassembly I determined that 1/32 70A viton is too rigid, thus I will swap it out with the 1/64 D60 neoprene for the time being. Unfortunately, the thinnest viton that McMaster had was 1/32. Since I would prefer to use viton, I will attempt to find it in a 1/64th thickness from another source.
Between the drill press, the extra carb and the various materials, I probably have $150 into this darn repair!
I'll provide an update after testing.
Drill press 2.jpgDrill press.jpgdrilled.jpgNeoprene sheet.jpgDone.jpg