Urban Express + Jamarcol Pipe = No Change

I recently purchased a Hobbit Jamarcol pipe through MA (thanks Raniel) for my '82 NU50m and tonight I bolted it on, made a quick bracket, and took her for a test drive expecting big things...

First thing I noticed was how loud it was compared to the stock pipe, but as I gave it gas I also noticed a loss in acceleration... Not to worry right, I read all about how the low end may suffer with a performance pipe on this forum. So I proceeded to ramp it up to full speed... this is where my heart dropped.

No power band, no increase in top speed, much slower acceleration all the way through.

What's the problem? I was getting a top speed of 29mph out of her before, and I was hoping for a cool 34-36 with the addition of the pipe. But now all I have is a very loud Urban that takes 4 blocks to get up to 28. I know a high-flow air filter should help, right? But that can't be the only issue, can it? Any adivice?

pic attached


Re: Urban Express + Jamarcol Pipe = No Change

here's a wider shot.


Re: Urban Express + Jamarcol Pipe = No Change

You'll need to upjet for the new pipe. At the very least lower the needle clip (raise the needle) a notch or two and adjust the pilot jet screw. Also, make sure your header flange has a good seal to the cylinder to take full advantage of the physics of the pipe.

Re: Urban Express + Jamarcol Pipe = No Change

I want to upjet and/or raise the needle, especially if I add a uni-pod, but it's a case of I know what to do, but I don't know how. Or that is to say that I have never done it before. Can you walk me through it?

thanks for the info

Re: Urban Express + Jamarcol Pipe = No Change

Hmmm, I would have thought it would have given you a pretty decent speed increase, even without the upjet. I guess maybe urbans were not jetted as overly rich as hobbits?

As far as riching up the mixture, unscrew the top of the carb where the throttle cable comes in, pull out the slide (cylindrical thing at the end) push the cable end out of the bottom, its in a little hole where it lives, then slide the cable through the cut in the side of the slide. Be careful though, there are some springy parts there that might make a break for it. After you have the cable off of the slide, push the little brass needle up, and a little W clip will pop out. When you have the needle, the little "hoodini" clip that sits on it and the W spring out, take the little c or hoodini clip, gently pop it off, and put it on the lowest notch on the needle.

Then put it all togehter in reverse order. Not that hard, but like anything just take it slow and easy your first time, make sure you remember where everything goes, and do it in a well lit uncluttered area.

Jetting is easy too, but I have never had a honda carb I could rejet and or needed to rejet, so I can't tell you where to get them.

Re: Urban Express + Jamarcol Pipe = No Change

Nice tate.

Bummer Adam. Bring it to the track this weekend and we'll get it going; I've got some NU jets and jet drills.

Does that pipe drag through turns? It looks pretty low.

Re: Urban Express + Jamarcol Pipe = No Change

i have that exact same pipe on the maxi and it hasn't made a difference yet, we'll see whtn the jcams intake and shit arrives.

throwing a kit on it this weekend, hope to have it going ~35-40 before i sell it to some kid that contacted me about it.

Re: Urban Express + Jamarcol Pipe = No Change

I really like the jamaraqui pipe on my express, but the one for my tomos is kind meh. I guess the fact that it is pretty much the only plug and play pipe for the express kinda means all it has to be is better than the uber restricted stock POS to be good.

PHADAM: You might want to consider getting the proma circuit pipe instead. If the jamaracol ends up not working for you for whatever reason, the proma circuit will rock your socks off. Gotsta loose the stand, but well worth it. Just gotsta rig up a kick stand of some kind.

Re: Urban Express + Jamarcol Pipe = No Change

Okay, so I naised the needle this morning (Thanks for the excellent instructions Tate) and the sound changed a bit, but no significant change in the acceleration or top speed. Is there a way to know just by the sound whether it is running lean or rich? Right now the pipe sounds really poppy especially when I let off the gas, and seemed to 4-stroke (I'm not quite sure if I'm correct, the noise suddenly changed to a bogged out sound) when I went down a hill, but stopped, and kept accelerating at the bottom of said hill.

Also, I'm planning on getting a uni-pod filter, but I'm wornding if there's a way to test if it will even help my situation before I spend the $$. Can I drill some holes in the stock air box? or is that just a bad Idea?

Derek: What track are you talking about? I may be up near you this weekend, but not sure yet. Also, the pipe does not drag on turns. It is much lower that the stock pipe, but I'm tall and took the pictures standing up so it looks worse than it is.

One more thing, would removing 3 of the 6 variator weights help at all? I know it will increase acceleration, but could it also help get the rpms up into the powerband range? Also, how easy/difficult is this to do?

Lots of questions, thanks for all the insight guys.

Re: Urban Express + Jamarcol Pipe = No Change


Re: Urban Express + Jamarcol Pipe = No Change

Okay, I went home over lunch to check it out a little more... I ran it around the neiborhood a bit with the Airbox cover off to allow more flow (don't worry, I rubber banded the filter on) and was able to get it up to 32 mph. Took a few blocks and it seemed a little bogged down, but I got her there. Happy, I turned around to go home, and as I slowed to a stop the engine died and would not restart. I walked it a block or two, and then it started up again. When I got home it died again as I came to a stop. Same thing happened with the airbox cover back on.

Isn't this a sign I'm running rich? Runs okay cold but dies as the engine warms up? I'm thinking of lowering the needle back down... thoughts???

Re: Urban Express + Jamarcol Pipe = No Change

well, pipe plus more air really leans you out, done any plugchops? start there.

Re: Urban Express + Jamarcol Pipe = No Change

Well, you have to be running super rich to have an engine die on you. If I had to guess, I would say either you are running out of gas, or you soft seized it. No big deal either way. I guess the best way to tell what the different in four stroke sound and lean boggy sound is to hear it for your self.

Four Stroke: Put a piece of duct tape or otherwise cover up part of the airbox that sucks the air in. Ride it around. That oscilating dadadadadadadadada sound is four stroking.

Lean bogging: Take off your air filter, and seriously only do this for like a block, ride around. It will be kind of a WAhhhhhg when you open it up wide.

You will sooner or later learn to feel the mixture on your bike. I guess I am not the best dude to give advice, as I soft seized my honda express today. I was about to hit 50 and it was like SKERP. Thank god it started back up. I am afraid to inspect for damage.

Re: Urban Express + Jamarcol Pipe = No Change

Tate, you were right, I was running out of gas. I know, I know, I'm an idiot. But, that said I've made some more changes (and have some more problems)

So, because I thought I was running rich, I moved the needle back down... not all the way, I'm right in the middle of the notches now. Next, I took the plunge and decided to remove 3 of the stock variator weights.

First ride, just took it around the block... sounds good. As expected, huge increase in low end, but as I got back to my house I noticed a weird cranking sound. I turned the key to off, and the engine was still running. After some investigation I realized that it was the starter still cranking (I have a deluxe NU50m). The only way I was able to get it to turn off was to disconnect the connection. So now I have electrical daemons! At least it still kick starts just fine.

In summary, I think I need to re-raise the needle and add a high flow air filter and I should be good. (based on the 32 I hit before I ran out of gas) I didn't get the chance to check the top speed as it is set up now cause it started raining. I'm planning on riding it to work tomorrow so I'll let you know.

Re: Urban Express + Jamarcol Pipe = No Change

Haha, don't feel bad dude, the reason I said that as a likely cause is because its happened to all of us.

"Dude, my bike is fucked!"

"Have you tried switching it to reserve?"

"Dude, you fixed it!"

I would say yeah, get the uni pod, put the clip at the richest setting and you should be all good.

Do a plug chop just to make sure.

I wanna say you need a unipod with the 1 3/4 inch inner diameter, but measure just to make sure.

Re: Urban Express + Jamarcol Pipe = No Change

I hope the starter wasnt cranking the whole time you were riding. Check out the starter button assembly for some mucked up contact points.

Re: Urban Express + Jamarcol Pipe = No Change

bk, I'm glad to hear you say that. I was thinking of looking in the button (mainly cause I couldn't think of anywhere else) hopefully that will take care of it.

and yeah, it was cranking the whole ride but it was just a couple blocks...

Re: Urban Express + Jamarcol Pipe = No Change

I drove her to work this morning... She's running like a dream, but the acceleration / top speed still isn't there yet. I got her to go up to 33 mph on a very slight downhill, but it took awhile. With the stock pipe I would hit 25 within one block, now it takes 3 blocks before I'm up to 29... will the high flow air filter really bring her up to par, or is there something else I could do to help?

I tried to plug in the electric starter again before I even put the key in, and it started crancking away.

Re: Urban Express + Jamarcol Pipe = No Change

Generally speaking:

The starter motor main pole usually has a direct connection to battery and the frame is grounded. The control system to turn the starter over is by having 12v going to the push-button, that activates a relay or solenoid, that makes the connection between the battery to turn over the starter motor.

3-steps: Button -- to relay -- to stater motor. Usually the problem is in the button, but otherwise is the relay or solenoid. Both of them have a tendency to stick or burn closed.

So, if you test the button to ensure that it's working properly with a continuity check using an ohmmeter, and it's good.

Then check to see if the relay (solenoid) is working properly. It should make contact when 12v is applied to the winding side (usually the third wire or smaller pole).

You already know that the starter is working: all the time.

Hope this helps you to troubleshoot an electric starting system. Just lose the elect start, kickers are fine. I wouldn't spend a dime on it if it were mine.

Re: Urban Express + Jamarcol Pipe = No Change

Any update?

Re: Urban Express + Jamarcol Pipe = No Change

Well- I got the electric starter working again. I just knocked the relay around a bit and, voila, it works again. I'm sure it may get stuck again soon, but for now it's good. Kicking is no big deal anyway.

As far as performance goes, I can say I'm fairly happy. I get up to 32-33 mph on flats, 35 on a slight downhill. I was hoping for more out of the pipe but oh well. It took me awhile to dial in the carb. I had originally raised the needle thinking the pipe would need it, but yesterday I dropped it back down to the stock setting, and now it sings. All that said my acceleration has suffered a lot. Removing 3 of the 6 variator weights helped the 0-10 but then it's a very slow climb to 25 before it variates again and ramps up to 30+

Now I'm looking for a good air filter... any suggestions? Everyone suggests a uni pod, but I'm not sure of the right dimentions. (links welcomed)

In the future, I'm thinking about new reeds to increase the power/torque in the lowend. Are there reeds available for NU50s, and if so how difficult are they to swap out? Also, should I just forget the reeds and think bigger carb? does the auto choke make that difficult? Thanks for all the insight guys.

Re: Urban Express + Jamarcol Pipe = No Change

💀Kim Jong illest💀 /

why not try some porting, and a carb upgrade? a pipe can only do so much for an otherwise stock set up. if your doing low 30s, you already got a pretty decent gain, all things considered.

Re: Urban Express + Jamarcol Pipe = No Change

hobbit reeds from treats work, might not be in stock right now

Re: Urban Express + Jamarcol Pipe = No Change

Matt Scout The Scouting Dcon /

After fiddling with the Keihin carburetor for a while, I chucked it and made an adapter to snugly fit a Dellorto 14.12 carburetor. It works great! Although depending on how you adapt it, you might have to chop the front mount of the rear fender. While I made my own adapter, I have seen a Motobecane shorty intake for Dellorto's mount up to the Honda flange style intake without much modification needed.

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