I have an '86 883 Sportster converted to 1200.
It has HD carb (been told it's a Kehein) not a CV.
As an 883 and after the 1200 conversion, it ran fine with a 155 main jet. Untill I layed it down & broke the carb. I replace it with same type carb but it won't run on a 155 main jet. Thru trial & error I got it running on a 125 main.
These carbs don't have needle valves to adjust.
I couldn't even find a jet smaller than a 145 so I took a 165 and ran a thin piece of wire thru it and bent it over in the throat & bowl so it stays in place. (I measured & did the math, so it is a 125)
The book says that all carbs from '86 - '90 883's, 1100's, & 1200's main jets range from 155 - 200. (My type carb on '86 & '87 models only, then they went to CVH carbs in '88)
Why won't mine run with any jet bigger than a 125 ???

 

Thats a good question.....I dont know what to tell you but are you sure it is not a rebuilt carb? Or, where ever you got it, is it possible that the old owner didnt try to "make a better carb" out of it? I ask becouse a bro of mine bought a S&S carb off of ebay, got it home, opened it up and wasnt what he thought it was......just a thought.

 

As far as I know (I just thought), the metering holes may be larger in this carb...?? But they are sealed with a plug at the factory and that plug doesn't seem to have been tampered with... Maybe it was a factory modification for '87 models (mine is '86)....??
I came to this conclusion because I just went thru this carb again last night.
I've been running this carb with the wire running thru the jet since about 2004.

 

Took my carb off & disassembled it, vatted it in B-12 over night. Got it back on & tested it out. It ran better than it has in years!!!
Done alot to the bike the past couple of months:Tightened up a couple oil leaks, diff (bigger) tank, diff seat, new speedo cable & drive gear, sealed the tank, new fuel lines, new high torque starter ($270.oo), new battery cables, new 'absorbed glass mat' battery on the way thru J&P Cycles.
I think I'm ready for rally season!!

 

Matt, if you really want to have a nice running machine see if you can find a more modern CV carb. There is a reason they changed to it. Both are made by Keihen but the CV is really a nice carb. I have done carb and intake upgrades for a friend's 84 evo. He was really happy with the upgrade. Check your dealers or indy's and see if they have some take offs laying around. You can usually find them pretty cheap.
You're going to like that AGM battery!