Really lean running Therma-Quad 850, found this by accidentally closing choke.

[James E Vining]

Ok so this has got me really stumped, I have known the engine ran different then what I normally have but then again it does not have a Purple Shaft cam, Headers, 2 1/2" exhaust etc.
I was running the MH a few minutes ago with the rear wheels off ground, checking tranny, making sure rear brakes were working properly and of course letting the auto brake adjusters do their job since I over tightened the brakes awhile back, I've always noticed when I first start it and the choke opens up it runs a little rough like it was lean , I was assuming the choke was to far open and I needed to adjust it properly and just have not gotten to it.
But running it for like 10 min or so and at 195 water temp I set the engine to run about 2K and i noticed it sounded like it was trying to miss a little, when I went to reach down to see if i could tell what was going on I placed my hand on Carb which in turn closed the choke about 60% and all of a sudden it picked up RPM and smoothed out.
This caught me by surprise i expected it to die so I started playing with Choke while it was running at 2K and found I had heard the engine correctly it does act like it is lean and then when I close the choke it smooths out and picks up rpm.
Now I just thought about this, running a engine no load at 2K would I still be using the idle circuit? If so I think I know what may be the problem then
Just so ya know the way I set the engine at 2K was with a Sunpro Super Tach II and I used the idle adjustment screw and screwed it in until I got to 2K
O heck I should've backed off idle adjustment screws 1-1/2 turns and seen if that changed anything but now its to late neighbors would freak.
I am wondering I need to check I assume Quiet time is from like 9 PM to 7 AM maybe it is actually 10 PM

[James E Vining]

I tried a couple different things and nothing worked, I know I put the O rings in the primary jet spot in the (Plastic like doodad that holds the fuel and the primary jets I believe I have become Tarded).
I rebuilt it back in 2010 as I was planning on finishing it along time ago but health issues/lack of will power/ etc. stopped me from that plan.
It never had any Fuel in it till a couple months ago whenever I fist started posting on here again.
I am guessing either the o-ring things were the wrong size as I remember having 2 sets of 2 in the kit or perhaps one of them kicked sideways.
Heck I don't know but I guess i should remove carb and dissect it, oh and make sure floats are not set to high somehow

[legomybago]

You have a vacuum leak issue sounds like to me.....

[James E Vining]

I would think with a Vacuum leak I would have a lower Vacuum then 20 Hg when Idling and at the rpm where I noticed the issue, My first thought was that I had a vacuum leak too.
I think I will disconnect and plug the PCV and Brake Booster and see what that does first before removing and Dissecting carb.