Carburetor from hell

Real Deal Neil /
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I got a "Revolution" carb (https://qt50.net/honda-nu50/honda-urban-express-revolution-carburetor/) the other day. It has become my worst enemy.

Installing on bone stock 1982 Honda NU50 Urban Express. With stock carb, was running about 25mph with 220lbs of fat ass rider but always a little rough and seemed like the autochoke and bystarter were always interfering with smooth fueling. So I got the Revolution to upgrade but it flat out won't work.

The low speed circuits seems to more or less work, but that's it.

Throttle cable is not too loose, not too tight, and I can see the throttle slide goes all the way down with no throttle, all the way up with full throttle. The jet needle slides into the needle jet just fine. Tried with the jet needle with the circlip in the second notch down as the carb came, then all the way to the top, and last with the circlip on the lowest notch. Made no difference. The needle jet is not bent and is held properly by the little v shaped clip thing.

Removed the exhaust and tried it that way just in case it was clogged. No help. It just won't get the RPMs up. Top speed is now 12.

The ONLY time I could get any real response is when I started it up with the chamber cap and throttle slide/needle jet assembly removed (ie, just open air on top of carb). Without the chamber cap on the low rpms about the same, but when I mostly covered the air inlet with my fingers or with the choke on at about 3/4, air would rush in through the top of the carb's open throttle chamber and rev right up, giving me that nice "zing a ding ding" you should hear from a two stroke when it's revved up.

So that's the problem. I own 11 carbureted engines, several of which are 2 strokes and am usually a pretty good wrench. I don't have any kinked fuel lines, the spark plug works and is gapped and installed correctly, the throttle cable and mechanism are just fine, compression is fine, carb is seated against intake manifold, no air leaks, etc. And like I said it more or less ran pretty good with the stock setup, just rough like a lot of old mopeds that spent most their life just sitting. Stock oil pump is out of the equation, routed return oil line to intake line and running about 40:1 premix.

Any ideas? Usually don't give up on a project until it's fixed but running out of patience and ideas with this carb.

This isn't something I can spend a ton of money on since I'm an out of work tour guide so just telling me I'm stupid for buying the revolution carb and that I should get a fancy italian carb, intake, pipe, reeds, big bore kit, etc. isn't gonna help here. I've got fast bikes, just want this one to run smooth.

Thanks for any ideas!!!

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