Solex 40 PDSI Rebuild and tuning

[71roundie67mgb65spitfire]

Hello All, 

I have the original Solex 40 PDSI carb on my 71 2002 (all original) and the carb is sputtering to the point where it definitely needs a rebuild (rough idle, stumble when rolling onto the pedal after coasting). I was wondering if there is anything I can do to the carb while I rebuild to give the car a little more oomph. I am well aware that I can achieve this with a weber setup, but the car is all original and I want to keep it that way. I have heard you can switch jets out on these solexes, although I feel like the main limitation of this carb is the lack of airflow due to the single barrel. 

 

Thanks in advance, 

Chris

[Slavs]

The best thing you can do to the carb is to get it to work correctly. The most common problem, although easily fixed, is   A clogged or partially clogged idle jet. Over time the small piston attached to the lid will punch a hole through the lid, rendering the carb almost useless unless you replace the lid. The needle valve on the lid also gets dirty over time, causing the float to get stuck. The carb body also warps at the mating surface with the bottom butterfly / throttle assembly, resulting in an air leak. And, most butterfly / throttle assemblies are worn at the shaft, resulting in an air leak. Some people attempt to adjust the air fuel mixture and in frustration turn the adjustment needle all the way in and further torque it into the throttle body, rendering the adjustment and throttle body useless. Back in the day they made spare throttle bodies, both factory and aftermarket, but they are nearly impossible to find. A machinist can repair it, though. This carb is a very good carb, but 50 years of use takes its toll. Do not replace it with the 34ICH Single barrel Weber. It is too small for the 02 despite being advertised as a replacement.

[71roundie67mgb65spitfire]

Thank you for the info. I don't think my carb is warped or there is a hole in the lid. The throttle shaft is likely worn however as my car has over 100,000 miles on it. I haven't seen a rebuild kit with a new throttle shaft however, and I haven't seen any good factory original replacements online. Any suggestions?

 

the symptoms of my car is that I cannot set the mixture accurately to get it to idle properly. After the car warms up, it runs and idles worse. It also stumbles when I get back on the throttle after coasting or cruising. I am guessing this is due to a clogged jet. Like I mentioned, I want to keep the car factory original so I will need a complete rebuild kit, or a carb that is in good working order while I work on mine. 

 

[SASH_2002]

I'm having similar 'challenges' with my car right now.  I'm pretty sure the throttle shaft has worn as mentioned above.  

So my question is - do I replace this for a reconditioned at £250 (Jaymic) or is there an alternative Webber / Delorto at half the the cost...?  Looking for a budget solution right now. Also want to keep the car as stock as possible, is do not want to change manifolds etc...  

 

Thanks 

S

[Son of Marty]

Well both the Weber or Delorto will fit the manifolds But by the time you get them tuned and running right I don't think you'll be saving any money.

[SASH_2002]

Im up for doing some homemade tuning if the replacement Carbs are worth it, like you say.  Problem I have this evening is that I have no idea what I'm searching for as a replacement.  * my bench mark is a swap with Jaymic for reconditioned Solex - this is a fruity option.... Im just being very Scottish and looking for a cheaper option!

 

[tech71]

As long as the butterfly shaft itself is not excessively worn, your most frugal option would probably be to refurbish your carb yourself or have a specialist do it. Many carb kits available on Ebay from both US and Euro suppliers. Some of them include butterfly shaft bushings.

Bushings are also sold separately

https://www.ebay.com/itm/BMW-SOLEX-36-40-PDSI-CARBURETOR-REBUILD-KIT/291283557982?epid=1853317858&hash=item43d1da5e5e:g:kCkAAOSwcF9UVNLR

https://www.dellortoshop.com/contents/en-us/p3203_Generic-Throttle-Shaft-Bushings-8-mm.html

I doubt you will see much if any, noticeable tuning improvements with an aftermarket single barrel carb. If you are going to invest in a new carb it really should be a 32/36 Weber. Not a Chineesim knock off.

 

My first 02 had a single barrel solex installed. Good carbs, simple.

 

 

Edited May 22, 2020 by tech71

[SASH_2002]

Thank you Tech71,

 

I suspect that it is the butterfly shaft as this had been called out by my 'guy who knows' apparently just worn and leaking air.  Thanks for the link, that kit looks interesting - I haven't seen before with shaft bushings.

 

I'm not looking to 'boost' performance, just want to get the car running good.  At present it just splutters as I change gear, especially into second gear, so need to floor it a bit to get the tickle to go, then she's fine.  Rest of the engine has had a good look over hence concluding that this is the problem (Without going into a tom of detail!)

 

Cheers