So on my journey to solving some tranny/power issues, I noticed a pretty loud "sucking" noise coming from behind the carb. It sounds like a bad vaccuum leak but when I sprayed some carb cleaner around there there wasn't any idle change. I didn't spray a whole lot because I got spooked when a small flair-up ignited on the heater return line .

It's hard to tell where exactly it's coming from- it's definately behind the carb between the air cleaner and the manifold, so I'm wondering if it's the actual carb I'm hearing...

...is it really that loud!?!

I have the same thing, I have found that it is a little diaphram thingy no the back of the carb. I cant remember what I did, but thats prolly what your hearing.

I have the same thing, I have found that it is a little diaphram thingy no the back of the carb. I cant remember what I did, but thats prolly what your hearing.

I know the diaphram you're refering to. So that's normal vacuum noise coming from there?

... it's definately behind the carb between the air cleaner and the manifold, so I'm wondering if it's the actual carb I'm hearing...

 

Have you Checked the Positive Crancase Ventilation Valve (P.C.V.)? is in the Path that you mentioned above... Maybe it has a Worn / Weak Hose...

I Suggest to Check the Hoses and the Carb´s Adjustment to its Base.

Good Luck!