1983 Nu50 : Pros/Cons of adding cylinder kit and questions

I got my wife a 1983 Urban Express last year and it's always been a little finnicky. I tuned the carb, cleaned it up quite a bit, swapped a bx31 belt on, and it was running 40ish on level ground with her piloting it. This year I decided I was going to go through it and add a cylinder kit, new carb, etc. I recently purchased an Athena 47.6mm 70cc kit and an curious if that's overkill for what she will do on it. She really wants it to be reliable and run 45-50MPH.

I also looked at the DR kits, but when I ran into an Athena on amazon for $139 I thought I couldn't pass it up. Now that I'm ordering the remainder of the small parts that I think I may need I'm second guessing if I made the right choice.

It is true that I'll need a new head to take advantage of the Athena? Is the DR kit really that much more "plug and play" than the Athena that the factory head will be sufficient once cleaned up?

I'm assuming either will need a new carb (please tell me if I'm wrong) and proper jetting to run safely and reliably. How large would you recommend and and ideas on rough jet sizes to start with in Kentucky summer weather (85-90* and high humidity)?

Sorry for the barrage of questions, but I'm a little out of my element here. Any input is appreciated(edited)

Re: 1983 Nu50 : Pros/Cons of adding cylinder kit and questions

Captain Janeway /

I have kits on my bikes, but to me they are a little more fussy than stock. If you're getting over 40 on stock, you may want to leave it. Personal opinion.

Anyway on kits. I have DRs on mine and got 5000 miles on one before I blew a piston.

I use stock heads on mine but only because the squish is cut a little bigger to accommodate. You should probably get the custom cut head from Treats. I'm not sure of the exact one so I don't want to send you to the wrong place. Let's see if someone who's used it chimes in.

I've tweaked my stock carb and jets to get it to work, but most people seem to jump immediately to a VM20 and the intake it will need. You'll also need a bigger pipe.

This stuff adds up really fast. You're about to drop $400 - $600 in (including cost of that kit you just bought).

You may want to figure out what's fussy on the current bike. Putting on a kit and then having to troubleshoot an underlying problem will make you crazy.

Also, do some searching on back threads. You'll find a ton of great info..

Re: 1983 Nu50 : Pros/Cons of adding cylinder kit and questions

I pulled the cylinder on hers today and it's scored pretty badly. I certainly wouldn't re-use it after examining it. I've done a good bit of reading on the forum, but I supposed I was just hoping for someone who had the same setup and could give me a magic bullet, LoL. I suppose my main concern is that when she rides it and hits the kick starter that it will go and not die on her at a stop light. Power is secondary but a concern as well.

Re: 1983 Nu50 : Pros/Cons of adding cylinder kit and questions

Captain Janeway /

She's having to use the kick starter at a stop sign? Something's really wrong, but it could be from a whole bunch of places.

If the jug is really scored, hey you have a doorstop. You probably had little compression as well which may have accounted for it dying.

If you want to leave it stock, you could probably get a decent jug at a decent price since so many people kit. You'll need new piston, rings, needle bearing, etc.

Let's see if Jack Rutherford or DPC Ryan can give info on the Athena.

Re: 1983 Nu50 : Pros/Cons of adding cylinder kit and questions

I'm having a real hard time not just buying this head:

https://www.treatland.tv/ProductDetails.asp?ProductCode=CUSTOM-HEAD-037&CartID=1

With a spacer as a precaution contingent on clearance:

https://www.treatland.tv/ProductDetails.asp?ProductCode=MLM-hobbit-metal-spacer-942&CartID=2

And I'm considering this as a carb setup as well, but haven't sold myself completely yet:

https://www.treatland.tv/honda-urban-express-nu50-carb-XPRESS-YOURSELF-pack-p/nu50-carb-party-vm18.htm

Any chance of properly jetting the existing carb after a thorough rebuild and having it function optimally or is it just undersized?

If anyone has firearm questions I'm happy to reciprocate LoL

Re: 1983 Nu50 : Pros/Cons of adding cylinder kit and questions

> Captain Janeway Wrote:

> -------------------------------------------------------

> She's having to use the kick starter at a stop sign? Something's really

> wrong, but it could be from a whole bunch of places.

>

> If the jug is really scored, hey you have a doorstop. You probably had

> little compression as well which may have accounted for it dying.

>

> If you want to leave it stock, you could probably get a decent jug at a

> decent price since so many people kit. You'll need new piston, rings,

> needle bearing, etc.

>

> Let's see if Jack Rutherford or DPC Ryan can give info on the Athena.

That was a very rare occurrence. Seemed to happen a lot more often to her than it did to me. I could ride the thing any where and hit around 35mph if I tucked like I was on my CBR1000 haha. It's just way down on power this year and I suspect I need to adjust the clutch as well.

I'd rather spend several hundred dollars and make sure it's reliable and can maintain a safe speed than sour her on two wheels forever. After all, she did wreck a Vespa 150 once and ne another occasion had to take me to the hospital after a 50MPH highside on a liter bike. It's a miracle she wants a moped!(edited)

Re: 1983 Nu50 : Pros/Cons of adding cylinder kit and questions

Captain Janeway /

One setup is the stock carb (with the equivalent of about 100 jet--you can only buy up to 96, it's just soldered and opened up a little. DR kit with bigger squish cut into head. Weakends pipe (which looks like the sidebleed cheaper MLM (warning on these pipes, you may have to fiddle with them a little to make them fit), stock airbox using panty hose instead of that huge sponge. 45 mph

Two is basically the same except with a tweaked pipe instead of the big one. 42 mph

Three uses same cylinder, head setup, 16.6 SHA carb, huge airbox to shut the carb up. Goes about 45+. If you don't mind blowing your ears out you can use that tiny SHA airbox and go like 52 mph. Sidebleed pipe.

Going cross town I just need to be fast enough to stay basically ahead of the cars. I don't need a rocket.

Re: 1983 Nu50 : Pros/Cons of adding cylinder kit and questions

Captain Janeway /

> Andrew beaven Wrote:

> -------------------------------------------------------

> > Captain Janeway Wrote:

>

> > -------------------------------------------------------

>

> > She's having to use the kick starter at a stop sign? Something's

> really

>

> > wrong, but it could be from a whole bunch of places.

>

> >

>

> > If the jug is really scored, hey you have a doorstop. You probably had

>

> > little compression as well which may have accounted for it dying.

>

> >

>

> > If you want to leave it stock, you could probably get a decent jug at

> a

>

> > decent price since so many people kit. You'll need new piston, rings,

>

> > needle bearing, etc.

>

> >

>

> > Let's see if Jack Rutherford or DPC Ryan can give info on the Athena.

>

> That was a very rare occurrence. Seemed to happen a lot more often to

> her than it did to me. I could ride the thing any where and hit around

> 35mph if I tucked like I was on my CBR1000 haha. It's just way down on

> power this year and I suspect I need to adjust the clutch as well.

>

> I'd rather spend several hundred dollars and make sure it's reliable and

> can maintain a safe speed than sour her on two wheels forever. After

> all, she did wreck a Vespa 150 once and ne another occasion had to take

> me to the hospital after a 50MPH highside on a liter bike. It's a

> miracle she wants a moped!

After you're done dropping all this money also make sure you invest in a temp gauge. Until you get it completely tuned up, you want to be careful about letting temps go too high. Stock head you can go to about 400 degrees, but watch it after that. Also be careful with your break in so you don't seize your brand new top end.

Re: 1983 Nu50 : Pros/Cons of adding cylinder kit and questions

Gonna need longer cylinder studs with that head you linked to

Re: 1983 Nu50 : Pros/Cons of adding cylinder kit and questions

Jack Rutherford /

I think you got an

Athena kit for scooters

. I could be wrong but I doubt that will work on your urban express.

The Athena kit that would work looks nothing like what's on Amazon.

If that's the case, see if you can return it.

to get 40 or so, I assume you are not running the stock exhaust. If you are running the stock exhaust, maybe you're best first move after taking care of any piston/cylinder issues would be getting a performance pipe. Install that and re-jet and see if that makes you happy. Post pics of your current cylinder.

I've read a bit on the Athena kit and it seems that the general consensus is go with the DR kit as it is cheaper, performs well and doesn't require a spacer and any other fiddling that the Athena might.(edited)

Re: 1983 Nu50 : Pros/Cons of adding cylinder kit and questions

Jack Rutherford /

If you are searching for reliability with your build, generally reliability goes down as you get closer and closer to the redline (increase performance).

Re: 1983 Nu50 : Pros/Cons of adding cylinder kit and questions

I'm running both on different NUs right now. First and foremost listen to Jack re: the scooter kit (good call Jack). If youre still thinking Athena (corrent one), a few things to consider:

This is a moderatly high RPM alum kit. If youre running thru stock iron ones, theres a good chance you may inadvertantly fry this one.

VM18 rocks. Get some assorted jets around the 130 range. Will also need an intake and filter (or stack).

Its possible to use the stock head; a custom will serve you better as the bore is very different. You will need a base spacer.

Finally, maybe I missed it, but you'll want to swap out the stock exhaust for an expantion chamber; even a cheap one will be Ok (not great mind you, but better).

Re: 1983 Nu50 : Pros/Cons of adding cylinder kit and questions

Captain Janeway /

And if you haven't seen it-- Treats sale 18% off code noheadache.

Re: 1983 Nu50 : Pros/Cons of adding cylinder kit and questions

> Jack Rutherford Wrote:

> -------------------------------------------------------

> I think you got an Athena kit for scooters. I could be wrong but I

> doubt that will work on your urban express.

>

> The Athena kit that would work looks nothing like what's on Amazon.

>

> If that's the case, see if you can return it.

>

> to get 40 or so, I assume you are not running the stock exhaust. If you

> are running the stock exhaust, maybe you're best first move after taking

> care of any piston/cylinder issues would be getting a performance pipe.

> Install that and re-jet and see if that makes you happy. Post pics of

> your current cylinder.

>

> I've read a bit on the Athena kit and it seems that the general

> consensus is go with the DR kit as it is cheaper, performs well and

> doesn't require a spacer and any other fiddling that the Athena might.

I'm fairly certain I purchased the correct kit based on my research. It's Athena #009300

Re: 1983 Nu50 : Pros/Cons of adding cylinder kit and questions

What's your take on the DR vs the Athena overall? I never ran a compression test after purchasing, but it was obvious to me it was getting some blow by from day 1. I'll snap some shots of my cylinder and head after taking my son to school.

Re: 1983 Nu50 : Pros/Cons of adding cylinder kit and questions

Jack Rutherford /

overall take on Athena vs. DR kit discussed here

And this is probably the final word within that thread:

"Beyond that, malossi, polini and DR are all quite similar in performance, but the DR is just a way better value, and it takes a hell of a beating without complaint.

And the athena, without question was the fastest, all around, torque and rpm, unreal. but yea, finicky.

Really wanna try the metrakit derbi setup, expecially for the better cooling, and curious about the malossi H2O, but i'm gonna shut up now and leave with this to say

DR is the best value, easiest, most rewarding and most robust kit for the hobbit. with porting it'll shred with the best of them, but even as recieved it's a really great kit. it may be my favorite kit in all of mopeds."

I've installed two DR kits and then wanted to screw around with the Athena. I read this thread and was like - maybe later but right now I don't feel like I'm missing much. With any of these kits, you've got to have a temp gauge and keep a vigilant eye on it especially up hills. And you've got to be willing to dial it in so that it runs relatively cool for the most part. You'll still get your blips now and again. Maybe your exhaust bolts work loose or your cylinder head bolts need tightened and temps shoot up above 420F or more. whoever is riding the bike has to be willing to keep an eye on things or it will stall at more than just stop lights.(edited)

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