Maximizing low-end power/pop Urban Express NU50

I got these two bikes out of a barn. Both are 82' Urban Expresses. Both appear to have been parted out to varying degrees. They look better here than they really were. I'm completely green so have had to learn how to build them on my own. I've got one running as of now. It's mostly stock but with a SHA 15 carb and intake. I'm premixing. Hitting about 28 mph with flipped stock belt. Other than that it's all stock. I've replaced seals and think I've identified and fixed all leaks.

I've seen a lot of recommendations for performance mods but I'm not seeing a lot for what I'm looking to do. I'm a big guy at 250lbs and not looking to hit 45mph on this thing, I'd be happy at 35-40 as long as I got there fast. I live in a hilly town and want to get great speed off the line with strong power uphill.

I've experimented with pulling half the weight out. It obviously gave me more off the line but I didn't like the power loss on hills and just in general didn't like the feel of how it ran after. I flipped the belt and put a washer behind the variator plate which gave me a few mph without losing the low end I crave.

I'm looking at exhausts and new top end kits but again, most of the recommendations for exhaust are with top speed as the goal. That's not what I want. So I'm looking for recommendations for combo of kit and exhaust and likely clutch springs to achieve the pop and take off I'm looking for. (edited)


Re: Maximizing low-end power/pop Urban Express NU50

Beach Club Nick /

You want a big expansion chamber and a TJT if that'll fit on an urban express. I have a hobbit with a cranks pipe and a TJT and I can wheelie it at pretty much any speed and it shreds hills easy.

Re: Maximizing low-end power/pop Urban Express NU50

Captain Janeway /

I have big hills in my area too. Use a GY6 clutch with red springs and a yellow contra spring.

I'm just using a DR kit lightly ported.

I weigh much less than you, but that clutch works well.

Re: Maximizing low-end power/pop Urban Express NU50

i love the proma on there but it'll cost you the kickstand

Re: Maximizing low-end power/pop Urban Express NU50

when i first got my urban express, it had the stock belt that was so worn down it was fitting way down in the pulley, and it predictably had pretty good take off. only 28mph topend, but I would call it "peppy." I have been pretty happy with the people's pipe. i briefly ran it with the stock belt, lighter weights, this pipe, and stock jetting. pretty decent off the line for a completely stock cylinder.

the bx31 gives you that top SPEED but considerable low end power loss

Re: Maximizing low-end power/pop Urban Express NU50

This stuff works great when everything is clean, true and properly lubed. Time and misuse kill all that.

There can be no belt smudges/scars/grooves/corrosion where the belt rides. Clutches must cycle smoothly... then you need a good belt.

Just for giggles, loosen the headpipe at the cylinder and test. Bet your top speed goes up.

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