<VV> General Information and Tips on Carbs

[Grant]

Here are a few recent happings/things that might save some angst concerning our carburetors.
- It seems that many (but not all) of the fuel inlet needles for Rochester carburetors out there in recent kits (back to about May of last year as far as I can determine) are too soft and tend to stick in their seats, preventing fuel from entering the carb. Sometimes tapping will free it up so fuel can flow and keep it lubricated, but not always. I have reverted to installing hanger clips on all them so the floats can pull them down instead of depending on gravity. Kits for them do not include the clips. Most everyone gets them from Walker Products with the needles number 779 on them. The part number for the assembles are 15-234. There are some assemblies 15-523 that have the hangers (and the same needle), but the holes are .101", compared to the stock .086" holes. The larger ones are standard in many Rochester 2 and 4 BBL carbs. If you have a kit, you can test the needle by inverting the seat as it would be oriented in the carb and pressing the needle into it with a bit of pressure. If it stays in, don't use it.
- Clarks is no longer suppling replacement throttle shafts for YH carburetors and I have not found another source or anyone willing to make them in small quantities. This means shaft bushings will be needed, and you will need a long reamer that extends through both ends of the TB (or a jig and drill press) to ensure the hole is straight and true. I have come across a few bodies where the factory holes were not drilled in the center of the housing and there is very little metal left after drilling. So, plan ahead and keep your old shafts. If they are too worn, the bushings can be installed deeper to get the remaining good part of the shaft inside them. O-rings can help in a pinch but can only be installed on the pump end of the shaft without grinding some metal off the lever end of the TB.
- I get quite a few 140 secondary cores where the accelerator pump cup has been removed, so there is no "squirt" upon quick acceleration. The only secondary carbs that don't use cups on the pumps were produced in 1968 and 1969. There are some examples out them out there, however, that still need them. The easy way to tell if your secondary carbs should have them is to check to see if there is an external rivet at the bottom of the pump cavity. Rivet means cup, and no rivet means no cup. Regardless, all secondary carbs with the rivet have only one squirter hole. There is no hole (or passage to it) on the later A.I.R. carbs. You can swap in earlier ones if you are experiencing a bog with heavy acceleration.
 - There are still some Rochester kits out there with buna accelerator pumps that are not ethanol-proof. Improved viton cups were introduced about 5-6 years ago. The way to tell the difference is the color. Buna is black and viton is blue. The buna cups will harden and stop working in as little as a year without a fuel additive. The few viton cups I get in cores have all been in good, flexible condition, but many buna ones are hardened to the point that they break when removed.  
Hope this helps prevent some frustration for you DIY guys. Happy New Year
Grant - The Carbmeister