About a year ago i decided to tackle a super cheap budget FCR kit, that cost me about 200 bucks if that. Because to be honest i'm not too interested in spending 1000 bucks for a carb.
The first most important thing. look for a used carburetor on the Face book market place,Craigslist, Offer up etcetera, generally you'll find many MX bikes that are constantly being parted out. Generally people That are parting out a bike don't really care about part value and will usually sell for cheap, since hey the bikes pretty much rotting in some shed or back yard might as well get rid of it. I've seen all kinds of FCR carbs, that are practically getting thrown away, Me personally i have about 4 FCR carbs, that I picked up for less that 50 bucks a piece. Thats a steal really, $50>$1000.
1. Carb condition/type
From my experience, carbs don't usually require extensive rebuilds, maybe just a simple rebuild kit. That its self only cost about 15 or so bucks, per usual if the piece is covered in an inch thick layer of grime. Its probably not the best bet, of course you're not going to get a brand new part, but hey money talks. nothing more than a can of carb cleaner can help.
I've also seen a lot of talk around the forums saying that you'll need a Euro FCR carb (The one with the removable intake bell) to get the ball moving, that is completely false. Japanese mx bikes are alot more common in the U.S. . So you'll come across the fixed intake bell a lot more. These work completely fine don't stress it. Another common misconception i see a lot is FCR size. I'm currently running a FCR 41 bored to 43.5MM and it runs completely fine albeit a little lean... Surprise surprise. Currently running a 42.5 pilot, and a 185 main.
Carb sizes varies from maker to maker, my old crf250r had a 40mm carb, the drz can run bigger, no issues at all. One Note Though Stay away from quad carbs, YFZ450R carbs will not fit at all due to the tps system getting in the way.
The old DRZ400E had a intake manifold that was made to hold an FCR. The kicker... the damn piece will end up costing as much as the carb if you're able to get on for under 50 bucks. since you're going to have to order through a parts site. Such as Suzuki Parts house.
PIPE, INTAKE E3,E28 $13.48
CLAMP, HEAD $3.45
CLAMP, CARB 3.45
Shipping is gonna be ridiculous, but what ever they have the part, and you don't☹️
Next you're going to need a FCR bell adapter, you can pick them up on the TT classified page or on ebay. I've seen them go for about $60 or so. I don't think anyone really needs the CNC Adapter, its another 30 bucks. The cast plastic one works fine, you do need to seal it with gasket maker, when installing it to get a complete seal.
You're finally going to need a new set of cables and a twist Throttle, I tried getting the stock ones to work, but to my luck it didn't work. I got mine for about 35 dollars and i got them in the mail about 3 days later.
The hot start also comes into account depending how picky you are about your set up. i just plugged mine with an engine bolt.
I also recommend getting a Non Vacuum petcock, it only cost about 10 dollars and you don't have to deal with setting up a vacuum nipple.
And thats about it really my project cost me around 180 dollars and 3 days of down time, also you're gonna have a blast getting the damn thing to fit in the bike but it'll fit. unfortunately i dont have any pictures to show. happy hunting peeps