Enrichment Valve

[ManiacRider]

I started rebuilding the carbs on my 83. Have a question for those experienced with these carbs. The "air cut off valve" or sometimes called the "carb enrichment valve" is causing some concern. The plastic/rubber diaphragm seems to be a little rough. It's not very flexible and the internal side appears to have the surface cut a little. There are no holes straight through the material just that internal side of the diaphragm isn't in the best shape. I don't know how this item is supposed to look. The carbs appear to never have been touched since new as the anti-tamper screws on the carbs don't appear to have ever been turned. Should these valves be really flexible? Will having them in a rough shape still make them usable? I've found replacements range anywhere from $16 all the way up to $67 each. If I don't have to replace them I'd rather not but will if necessary. Any input is appreciated.

[bongobobny]

Their main function is with the choke circuit, it's up to you, and how well the choke works, to decide if you want to spend the money...

[MiCarl]

The air cut off valve is a different thing than the enrichment valve.

 

The enrichment valves add fuel in place of a choke for cold starts, in fact the lever that operates them is labeled "CHOKE". They do not have diaphragms but are plungers with a seal on the end.

 

The air cut off valves remove some air from the idle mixture at high vacuum, which occurs when coasting. This is done to reduce lean backfire when the throttle is closed and the motorcycle is pushing the engine. They are operated by little diaphragms. This sounds like what you are describing.

 

I don't worry about air cut off valve diaphragms unless they have a hole or are torn.

[ManiacRider]

The air cut off valve is a different thing than the enrichment valve.

 

The enrichment valves add fuel in place of a choke for cold starts, in fact the lever that operates them is labeled "CHOKE". They do not have diaphragms but are plungers with a seal on the end.

 

The air cut off valves remove some air from the idle mixture at high vacuum, which occurs when coasting. This is done to reduce lean backfire when the throttle is closed and the motorcycle is pushing the engine. They are operated by little diaphragms. This sounds like what you are describing.

 

I don't worry about air cut off valve diaphragms unless they have a hole or are torn.

 

Thanks for clearing that up. The internet has the same part with the two separate names which caused my confusion. However, yes it should be the air cut off valve. Thank you.