NU50 Rebuild vs Kitted

Smitty Werbenjegermanjensen /

I have come into possession of a good ol Urban Express. Came running and in one piece, is currently sat in many pieces around my garage for funzies.

I estimate I am about the 4th or 5th owner of this particular noped, as there appear to have been many "repairs" and slathered silicone in place of a $5 dollar gasket.

Sometime in it's life, someone either attempted to give it some juice or was simply simplifying it because the oil tank was removed and the fuel injection was disabled. Then, the owner that I procured it from said he had been running it for years... without premix. Seemingly unaware. And to my amazement, it WAS still working, kicked over the first friggin time.

So upon inspection the top end is... I cannot actually tell. The piston itself is scratched to high hell but the rings looks fine(?) and the inside of the cylinder feels kinda smooth(?), but who tf knows I can't get a picture worth a damn. How much are pistons supposed to wiggle inside the cylinder?

So I have some options ahead of me, and the foresight to know I don't know which path to take:

The bro in me wants to slap as much cool shit as possible on it; 70cc kit, mikuni carb, variator the variator out of that variator, fancy crank cause I'd rather it not explode, and get a custom-ish pipe made cause dammit I want me an expansion chamber but my autistic ass ears are having none of that 2 stroke nonsense. Then paint the shit out of it cause I saw Zixor's NU50, and, good god, that's sexy.

But also, blue anodized hardware isn't going to survive around me and my ghetto tools, you can't have just one of those things cause 70cc's requires this and that, powder coating requires going to that one powder coating shop down the street and there'll be a weird interaction about how I'm the guy that delivers their pizza pretty much every Friday at 12:30, and that's anxiety I don't need.

Then the sensible, forward thinking me know's that what I actually want is a dual sport or small ADV bike (310 gs just looks... mhmmmm), so shut up and just have some fun fixing the thing to then sell for a decent profit, which is what I have been doing so far. Don't go obsessive, put on a 50cc kit, and down-jet the carb cause some sources say the factory jet is too large. You've already got a challenge to clean the damn thing, cause dear god, it was made in 82 and hasn't been cleaned since. The gunk is so thick in some areas a shovel would be more efficient than the wipes you bought.

Then there's a small squirrel in my head wondering if the 60cc kit is a drastic step down in tuning requirements from the 70cc kit, because in that case I might be persuaded towards that if I don't need a new carb. Or, if it's just as much work and 70cc kit is better value for time spent tuning, in which case I'll stick with the 50cc.

Re: NU50 Rebuild vs Kitted

Captain Janeway /

If you don't really want it and want something else, get it running really well stock, sell it, and get what you want. It will be faster and cheaper.

I'd open up that top and see what it looks like. If halfway decent put in new rings, clean the car and see how it runs. Then clean and sell. A good stock bike let's someone else deal with tuning, kit, pipe...

https://drive.google.com/folderview?id=1vxdUocvohov-VU1KVuOY-9YquFpw7fok (edited)

Re: NU50 Rebuild vs Kitted

Smitty Werbenjegermanjensen /

How do I tell if a cylinder is wrecked? Aside from being in multiple pieces. All I see is metal with scratches. However, from what I understand, scratches are supposed to be somewhat normal, but also if there's too many or too deep that's bad. But maybe that fact the scratches are visible at all is a no-no? Running blind a bit (edited)

Re: NU50 Rebuild vs Kitted

> Smitty Werbenjegermanjensen Wrote:

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

> How do I tell if a cylinder is wrecked? Aside from being in multiple

> pieces. All I see is metal with scratches. However, from what I

> understand, scratches are supposed to be somewhat normal, but also if

> there's too many or too deep that's bad. But maybe that fact the

> scratches are visible at all is a no-no? Running blind a bit

Post a couple pics of the cylinder , from the top and bottom .

Re: NU50 Rebuild vs Kitted

Smitty Werbenjegermanjensen /

Re: NU50 Rebuild vs Kitted

Captain Janeway /

I don't think it looks bad. Do all that other cleanup and ring change (don't forget your premix at 50:1 if you have no oil pump/reservoir). See how it runs. If it runs like crap it could be a number of things, but you may want to start by picking up a compression tester to check it. Should be about 120.

pd--does that look like blow by to you on the last piston picture?

A well-running stock Urban is pretty bullet-proof.

Re: NU50 Rebuild vs Kitted

Blow by ??? If it is , it doesn't seem like much . It might just be lighting , but ???

The cylinder looks pretty good . I'd clean it up with a light hone . Check all edges for decent chamfer .

The piston has obviously seen the lighter side of seizing .

I'd pull the rings . Clean the landings and smooth the skirts . Check the ring end gap after the hone to see if they might be useful .

Re: NU50 Rebuild vs Kitted

Smitty Werbenjegermanjensen /

Aight so I'ma just get a whole new piston: https://www.treatland.tv/honda-hobbit-METEOR-40mm-stock-piston-p/hobbit-meteor-stock-40mm.htm

Cause the ring set Treats sells appears to have some fitment problems judging by the reviews: https://www.treatland.tv/honda-hobbit-40mm-piston-rings-p/hobbit-stock-rings-40x1.5-fg.htm

and OEM stuff is in the pricing territory of just getting a whole new top end.

Honing tool is 10 bucks on Amazon

https://www.amazon.com/dp/B01BHO9ZDK/

There are a ton though but hopeful that one'll be good enough. The brand appears to have an actual storefront for selling automotive specific tools, which is a good indication that it's not one of those allegorically generated Chinese amazon bot things.

> P D Wrote:

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

> Clean the landings and smooth the skirts .

Come again?

Re: NU50 Rebuild vs Kitted

Smitty Werbenjegermanjensen /

> Smitty Werbenjegermanjensen Wrote:

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

> one of those allegorically generated Chinese amazon bot things.

*algorithmically

Re: NU50 Rebuild vs Kitted

Smitty Werbenjegermanjensen /

https://imgur.com/a/iQKRdzf

Added some more photo's, after I took the cylinder out.

Re: NU50 Rebuild vs Kitted

> Smitty Werbenjegermanjensen Wrote:

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

> > P D Wrote:

>

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

>

> > Clean the landings and smooth the skirts .

>

> Come again?

If you'r e buying a new piston , it doesn't apply .

And , you might check with an auto parts store that has a loan a tool program to see if they have a small enough hone you can barrow . You need to know the size of the hole being honed and the smallest size the hone will hone . (edited)

Re: NU50 Rebuild vs Kitted

Captain Janeway /

> Smitty Werbenjegermanjensen Wrote:

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

> https://imgur.com/a/iQKRdzf

>

> Added some more photo's, after I took the cylinder out.

Pd: on the first piston photo, isn't that blow by? Just curious. I'm not sure if these would be the markings for it.

OP: sorry, just wanted to ask a question.

Your PO did interesting things. Of that was a stock Honda piston I don't see the expander ring with the others. I'm amazed this didn't completely seize up with no oil.

Re: NU50 Rebuild vs Kitted

> Captain Janeway Wrote:

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

> Pd: on the first piston photo, isn't that blow by? Just curious. I'm not

> sure if these would be the markings for it.

>

It sure looks like blow by to me . Actually , rather heavy blow by . Maybe because of rings stuck in the landings or a misshaped cylinder . It might be a good idea to size over on the piston and have the cylinder bored to it .

Measure the cylinder in multiple places to be sure .

Re: NU50 Rebuild vs Kitted

Captain Janeway /

> P D Wrote:

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

> > Captain Janeway Wrote:

>

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

>

> > Pd: on the first piston photo, isn't that blow by? Just curious. I'm

> not

>

> > sure if these would be the markings for it.

>

> >

>

> It sure looks like blow by to me . Actually , rather heavy blow by .

> Maybe because of rings stuck in the landings or a misshaped cylinder .

> It might be a good idea to size over on the piston and have the cylinder

> bored to it .

>

> Measure the cylinder in multiple places to be sure .

Thanks pd I thought so.

OP, I hope that made sense to you in regard to your build.

Good luck

Re: NU50 Rebuild vs Kitted

Dirty30 Dillon /

If you don't have access to a affordable boring service, replacement is typically easier than rebore.

You can buy a DR kit and call it a day.

Re: NU50 Rebuild vs Kitted

Smitty Werbenjegermanjensen /

She Runs and Rides! Crap at idle though so looking into that. NU50's have got this weird af vacuum auto choke thing and it's really weird.

Re: NU50 Rebuild vs Kitted

Smitty Werbenjegermanjensen /

https://imgur.com/a/BjoIVzN

Incase anyone wants to see what I did, first time honing a cylinder so I hope I did decent enough. She runs at the least. New piston fits perfectly and ring gap came within spec outa the box.

Re: NU50 Rebuild vs Kitted

Captain Janeway /

The honing usually looks like this with a cross hatch (second photo). https://www.revzilla.com/common-tread/cylinder-preparation-explained

If you have it running that's great. You get the idle adjusted?

Re: NU50 Rebuild vs Kitted

Smitty Werbenjegermanjensen /

That guide has a lot of information in one place that it took me hours of research to find. Slightly annoyed I didn't find that one.

The idle is proving tricky. Fiddling with the idle screw on the carb is yielding funny results. Still working on it. I don't want to have to take it off again, I cleaned it pretty thoroughly the first time but I think it has something to do with the idle jet tube thingy.

Re: NU50 Rebuild vs Kitted

Captain Janeway /

Put the bike on the kickstand then turn the air screw (the one to the left), out 2.5 turns.

Adjust your idle screw until the back wheel moves a little.

Go for a short ride to warm it up.

Now adjust that screw until the wheel either doesn't move or just moves a little. You're shooting for a nice little purr not choking, cutting out, etc.

You'll get the hang out of it.

I usually carry a tiny screwdriver for a little while after a big job on the bike just because it may need a little roadside adjustment on idle until I get it just right. that's just me though, some of these guys are a whole lot better tuning.

Re: NU50 Rebuild vs Kitted

Smitty Werbenjegermanjensen /

Aight so, it's doing the same thing. Pretty much no matter what I do (with the wheels off the ground), one of 2 things happens: It either idles high until I give it throttle in which case it just sorta kicks off and revs uncontrollably, or, it idles low and gets lower and lower until it dies. There is no point at which in adjusting the idle screw, it idles calmly. I'm also having trouble finding where to adjust the little lock nut bolt thingies where the throttle cable meats the actual throttle handle, so I wasted about 20 minutes messing with that to no real avail.

This leads me to believe something is off with the idle jet, however before I go down that annoying route I will give it another go after finding this: http://qt50.net/wp-content/uploads/2016/01/nu50-geninfo-lub-maint.pdf

On page 28 it specifies a way to set the Idle, I'm going to try that specific strat and see if it works.

Re: NU50 Rebuild vs Kitted

Captain Janeway /

Not sure what you're doing with the throttle cable. Do you think it's stretched? sticking?

since it seems to change every time you open the carb I have to ask: are you putting the slide in right (p. 41in the manual). If you put it in backwards it's going off to the races because the slide won't move properly.

Look into the carb with the airbox off, twist the throttle, and let go. You should see that slide move up, then snap back down when you let the throttle go. When you're looking in, you will see a gap at the bottom of the slide.

If you've been playing with that cable, yeah you may have to spend a little time adjusting it now, but see if that slide's in correctly.

Re: NU50 Rebuild vs Kitted

Smitty Werbenjegermanjensen /

Clogged freaking pilot jet. Now she idles mostly fine, however there is some funkiness with it subtly revving and slowing, much less intensely than before though. Looking into that now.

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