Looking for NU50i upgrade advice

Recently picked up a Honda NU50i thats been garage stored since 2006. Read the forums and the wiki then followed Fred's guide. After a good carb cleaning, new plug and other general maintenance its up and running nicely. I still have 1 air leak between the cylinder and the pipe but I'm planning on installing a "DR 46mm 70cc cylinder kit", "MLM honda urban express NU50 next level STOCK pipe", and reeds. I get 25 mph uphill and 27 mph flats. I would like to maintain 40 mph if possible. Since its an Iowa model everything I've read points to the exhaust port shaping that restricts it so the new cylinder and pipe should "un-restrict" it. With Just those upgrades is 40 possible or should I look at other upgrades? Do I need a new carb? If so any recommendations? I'll have to rejet it, any idea where to begin? If I'm going about this wrong or you know a better way to go about it please let me know?

Re: Looking for NU50i upgrade advice

Jack Rutherford /

Here’s my Iowa engine with stock cylinder and vm18 carb with 67.5 main jet. You’ll need a bigger jet with dr kit. Get the Puc Honda head. Sell the stock carb. It sucks! Get the people’s pipe and not the lower level one.

(edited)

Re: Looking for NU50i upgrade advice

Jack Rutherford /
nu50party3.jpg

party is not over - race gears? belt? reeds? super spark plug? (edited)

Re: Looking for NU50i upgrade advice

46 mph with the stock cylinder and other mods, nice! Thats plenty fast for safely keeping up with in town traffic and looks easier to setup (minus gearing) than a whole kit. Out of curiosity anyone know roughly what to expect from Big Bore party 1 - 3? Could/should I use those packages as a base guide to upgraded over time? Belt, premix and peoples pipe first. Then carb, head, clutch until I'm happy and do a bigger kit if I still require more? What order would you recommend mods go? I appreciate all the help and info this is my first intro to the hobby so I'm trying to learn and do things correctly. I'd hate to buy, install and destroy hundreds of dollars in parts but I guess it's one way to learn.

Re: Looking for NU50i upgrade advice

If you don't research jetting and tuning. You will destroy your new parts....well maybe not the parts but definitely seize the engine.

When you get to jetting always start rich and work down.

Re: Looking for NU50i upgrade advice

Jack Rutherford /

So here's one way to approach the upgrade game.

1. Performance exhaust and bigger main jet.

Learn how to tune your carb with a new exhaust and how to mount a new exhaust as well as how to tune your variator/clutch/belt because you'll need to at the very least change the variator weights from the stock 78 grams to maybe mid-30s grams. Ride and evaluate. Want more after that?

2. Bigger carburetor. Jetting will be completely different. Learn to tune your new carb to your exhaust. Ride, enjoy and evaluate.

3 - Maybe you want more. go with bigger top end. Jet your carb again for the increased fuel demand. Battle heat problems. Consider getting custom cylinder head or just get custom, bigger cylinder head. Tune your variator again with even less weight. Try different belts. Maybe a new clutch and contra spring. Go wild!

other considerations for the Urban Express

4. racing gears - tune your variator/belt/clutch/contra again as needed.

5. Lace up a 16" rear tire - tune your variator/belt/clutch/contra again as needed.

Of course, I didn't mention possibility of different reeds, reed block and basic maintenance stuff like new tires, tubes, strips, brakes and beyond.

Re: Looking for NU50i upgrade advice

Ordered a people's sidebleed pipe and dellorto SHA 15.15 carburetor with lever choke and 80's, 90's jets. I'll start tuning with the pipe then add the carb and rejet again. Should I consider a new air filter? Right now its stock with new foam. Need to adjust the variator weights and put the BX31 belt on. I have everything to cap off and remove the oil injector. We'll see where I'm after that.

Re: Looking for NU50i upgrade advice

Jack Rutherford /

mid 70s jet on that SHA. bx31 will kill your acceleration - it's too long and wide.

Re: Looking for NU50i upgrade advice

People are still tuning Urbans around here? How nice. I've been meaning to get back to work on The Runaway Dirtped. Full on forgot about the racing gears, tbh

TWminimotoenduro.dirtped4.10.16.jpg

Re: Looking for NU50i upgrade advice

Jack Rutherford /

Got the urban fever!

Re: Looking for NU50i upgrade advice

Update since I've spent some time and money on my "Covid Express". I've been working on this due to having had too much time on my hands and figured I'd learn something along the way. I may not be hansom but I am handy and with my "Red Green" mentality I went ahead and got the Treats Level 2 party pack, Boyesen MOD dual stage reeds, new tires, brakes, and bx31 belt installed. I picked up some 4g and 8g rollers, currently running 6x8g. I have it jetted 68 (I have 50-100 even's). Installed a oil injector delete plug. 0-8 mph I feel is sluggish about 3-4 seconds after that it takes off to 35 mph quickly. Not a hill around can keep me under 32 mph and any down hill action takes me into the 40+ range. So far the information on this site has been enough to get me this far without issue. I'm running 40:1 pre mix with a BPR8HS plug and it seems okay but I admit I don't know why I choose that mix or plug other than I must have read about it somewhere or I made it up in my mind? I need to pick up a tach and temp gauge and I'm considering the peoples pipe. Any recommendations on clutch/spring variator/weight combos or anything else? So far I'm learning a lot and having a ton of fun. (edited)

Re: Looking for NU50i upgrade advice

Dirty30 Dillon /

Increase your clutch stall to get rid of the 0-8 mph soft spot.

Re: Looking for NU50i upgrade advice

Jack Rutherford /
treatslevel2.jpg

so this is what you got. what main jet are you running in that SHA carb? 6 x 8 = 48 grams. How did you decide on that weight in your variator? I think you need to drop it down to around 36 grams and see how it does. You could also change the clutch springs as well. 40:1 should be fine but you'll get an infinite number of opinions on that.

ok 68 main jet in an SHA on the urban. I would think you'd be mid seventies on the main jet. What temps are you running? What belt are you running as well?

and IMO, your plug is probably too cold. But if it works . . . .

Alright, you're running the dread bx31 belt. That's why your take off speed sucks. Get that nu50 belt on treats. That's what you want. Or you can find a washer and stick it on the end of the boss before the pulley half - effectively making your boss longer/wider and allowing that bx31 monstrosity to drop down in the front pulley/variator a little farther > giving you better take off but shaving some of your top speed. Actually, if you can get another one of the washers that is on the end of the gear right next to the variator that will work perfectly. (edited)

Re: Looking for NU50i upgrade advice

Jack Rutherford /

I used to refer to the bx31 as the Sitting Duck belt because when you pulled out into traffic it would leave you out there like a sitting duck until it finally spooled up.

Re: Looking for NU50i upgrade advice

Honestly Jack I think you may have indirectly given me most of the info I'm using. You and a youtuber "churioz" which I'm now realizing is also you. Belt it came with is okay. Inside out it's better but the bx31 out performed it all around. I had a few BX31's in the shop but I'll pick up a proper belt.

Stock weights are 79.24g with flat spots. Went to the 3 best looking stock weights then 6 new 8g weights. That's just all the testing so far. Since I also picked up 4g weights I'll try 3x4g and 3x8g for 36g total as suggested.

Fuel mix and plug I honestly can't remember why I chose it and now it's bothering me. The manual says "STANDARD BPR5HS and for extended high speed operation BPR6HS". Now I think I'll pick up a few BPR6HS plugs.

Jetting seemed low to me but I'm still learning. I'll swap weights and plug today and swap belt once it arrives. I'll update after I play a bit. (edited)

Re: Looking for NU50i upgrade advice

Swapped out the BPR8HS with a BPR6HS. Played around with jetting. 75 main with the stock Dellorto air box and it ran like crap as in barely. Remove the filter and it ran great. No real proformance change from running a 68 main with the filter.

I have a few questions now. What should I do air filter wise? I found mod on the wiki. What should I look at clutch wise? Not sure how higher or lower RPM's springs affect the ride. I assume that's what Dillon is recommending. (edited)

Re: Looking for NU50i upgrade advice

you will need a different clutch to use other springs, stock NU50 springs are unlike any aftermarket ones. 107mm is the clutch size you want, several options out there.

Re: Looking for NU50i upgrade advice

Jack Rutherford /

Since you have the weights already, I would lower weights in variator to somewhere around 36 grams and test it. And I would also try a different belt. And yes, you would have to get a 107mm clutch - typically gy6 clutch is sold on treats and will work.

Re: Looking for NU50i upgrade advice

with just the MLM people's pipe, stock carb, stock cylinder (no porting), and BX31 belt I get about 40mph on flats.

not an iowa model tho (edited)

Re: Looking for NU50i upgrade advice

Jack Rutherford /

People's pipe is true expansion chamber while the next level pipe is not. So you would see quite a bit of a gain with the people's pipe.

Re: Looking for NU50i upgrade advice

People's side bleed vs H95 side bleed pipe. Anyone have experience with the two? Offer any insight? I appreciate everyone's input.

Spark and mix wise I probably should have just asked Treats for the info to start with, they recommended B7HS with 50:1.

As for the air filter I'm planning on following the wiki mod and using some UNI filter foam with the large hole mesh backer. Any thoughts?

UNI filter foam

(edited)

Re: Looking for NU50i upgrade advice

Jack Rutherford /

I vote people’s pipe. I don’t think you get - err - wait. They dropped the price on that h95. $50 difference. Used to be over $100 difference.

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