I have tried to search this but could not find an answer.

I have a B20 with dual SU carbs. Today when I was cleaning the filters and spraying in some Seafoam I noticed that as I increased the throttle that one of the carbs would rattle. I am not sure exactly the name for it put the cylindrical piece that moves up as you throttle up. The good one, I assume, would go up with some pressure and come back down slowly. The other one would go up very quickly and then come down very quickly and rattle when the throttle wasn't just right. I hope that this make sense....

Is there an easy fix to this or is a rebuild in my future?

Ryan;

I don't know what seafoam is (I presume here that it's not something packaged at Miami beach!)...you might tell us what it is generically...and I don't know therefore if you should be spraying it on your carbs!

...but I would agree with other posters...it sounds like your dashpot is not dampened, and if your not aware that it should be, you may want to familiarize yourself with the workings of these carbs a bit...See: http://www.sw-em.com/su_carbs.htm

Cheers

Thanks to all.

Seafoam is an engine cleaner that you put a bit in the carb, crankcase and fuel tank. Had some good results with it.

Seafoam Link

Joe M in WV

There is supposed to be about a teaspoon of oil in the chamber above the piston. Unscrew the fill cap and top up as necessary. Be aware that overfilling will cause oil to squirt out the vent hole in the cap when the piston is raised. It might be a good idea to place a rag over the cap and lift the piston a few times after addiing oil.

Joe M in WV

Just so you don't have to go searching:

The carbs don't really care all too much what type of oil you use. Many people here use ATF, although SU has it's own "brand" that is expensive and hard to find not online. Use anything around 20SAE thickness.

Check the dampers for oil.
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Lee 75 244 (80k original miles) 79 242 65 220 project