Modifications for crazy low end power on my H2O NC50

Rob GasketFace /

I put a big kit on a tiny bike. Malossi H2O kit on a '78 Express. Problem is I'm frankly kinda' scared to push the little guy much faster than 40mph. So I'm wondering if I can push all that spare power to low end torque and do wheelies at all the stop signs. All sprockets are inside the transmission, so I don't think I can do it the easy way.

Any suggestions for upgrades or mods to increase my low end torque even if it's at the expense of top speed? This is my current setup:

Malossi H2O kit with Polini pump

MLM People's pipe

SHA 15.15 (I know I know...) with size 70 jet

Boyesen "stockish" two stage reeds

Stock points, advanced by changing point gap

3/8" holes drilled in clutch shoes

Oddly, it actually runs kinda hot right now. Coolant temps coming out of the head surpass 200F within a quarter mile of mild riding. Not sure what's up with that. Might be too advanced, might be lean, might have bad radiator flow. Still needs some tinkering.

(edited)

Re: Modifications for crazy low end power on my H2O NC50

Rob GasketFace /

Re: Modifications for crazy low end power on my H2O NC50

Although I haven't been tuning my h20 setup, I find many people report low-mid 200's water temp.

The only suggestion I could have made was to drill the clutch shoes. Or, run a circuit pipe but I don't think that will get you exactly what you seek. The engine can get you past 40, butnot by a lot and not for a long time either. It really is screaming pretty well up there but I have gotten mine to 43 air cooled.

The real answer is to try and find an nu50 engine. My nx50 swapped NC laughed at me for bitching out and only reaching 45~ last night on a teat run of a new belt.

Re: Modifications for crazy low end power on my H2O NC50

Derrick Oyervides /

I can go ahead and tell you from the start a 70 jet is way to small if it's a 70 cc. Friend of mine had a 92 jet on his express with a 12mm carb and sift seized it numerous times before I had the wide and to dial it in. With a 15mm carb I would say at least a 90 to 100 jet. His wasn't water cooled and didn't have a temp sensor either but I guarantee his was about 450 degrees. Even if it's water cooled it can still be damaged by running to lean even if it's at 200 degrees. Cars thermostats open at around 165-185 degrees. "Most Hondas I've worked on" and peak temp around 220 before the ecu "hondata s300" runs in limp mode with a check engine light. Up your main jet and do some plug chops and you should be fine. My friends express was a 1 speed so it revved really high at 40 mph.

Re: Modifications for crazy low end power on my H2O NC50

But most big v8s run 220~ not all engines are the same. And you were jetting in the 90s to combat massive heat. If I were to put an sha on a bike I am familiar with (that has one) with a kit and pipe, the jetting would be in the high 60s to low 70s.

And the 1 and 2 speed have the same final ratio so there is no difference. And, the s300 you have dealt with has a user programmable threshold that came defaulted to that temp by Hondata, likely extrapolated from the factory ROM of a stock ecu. I'm not saying they operate under different laws of physics but there are different things involved, like the cooling ability of an aluminum sleeve vs cast iron.

Re: Modifications for crazy low end power on my H2O NC50

pretty crazy looking setup, love it. got a 2 speed nc50 i'm working on now...

so, it's the malossi kit for the hobbit?

and i'm sure you know, but the rear tire is on backwards...

Re: Modifications for crazy low end power on my H2O NC50

Derrick Oyervides /

I don't tune my oeds off heat range, yes it is in mind but I dial in my carbs with a AEM wideband. Getting the air fuels at WOT between 12.5 - 13.5. My guess would be that if he has a 70 cc piston kit that his air fuel ratios would be lean with a jet size of 70, but I'm not there and he doesn't have a wideband to check his air fuels that I'm aware of.

Re: Modifications for crazy low end power on my H2O NC50

Moby Express /

Never going to get crazy low end on a 1 speed express. Even the two speed express isn't much better.

NU50 bottom end even stock would probably smoke a modded express up to 30 all day.

Re: Modifications for crazy low end power on my H2O NC50

Tune the clutch.

Re: Modifications for crazy low end power on my H2O NC50

He did.

Re: Modifications for crazy low end power on my H2O NC50

Rob GasketFace /

> pretty crazy looking setup, love it.

Thanks man, I spent a lot of time on aesthetics. Almost everything is powder coated. Yeah I know the rear tire is on backwards, but good eye! It was such a bitch to get on that I'm not looking forward to turning it around.

The size 70 jet produces a bunch of white smoke at idle so I figured it was rich enough, but that could just be wonky SHA tuning, which is richer at low rpms. Still need to do a proper plug chop, etc.

I know that big carbs are mostly for top end, but maybe a more tuneable 16-18mm carb, like a PHBG or a mikuni VM, might help me get more out of my low end?

Another possible mod is a CDI with a curve. When I had a cast iron 70cc kit, I could get decent low end torque by advancing the timing, but my temps would skyrocket at high rpms.

Re: Modifications for crazy low end power on my H2O NC50

The SHA is certainly why you have smoke at idle. One jet cannot cover all ranges, especially when you are pushing the limits of what the design can support.

Re: Modifications for crazy low end power on my H2O NC50

a more tunable carb could help w/ low end too

Re: Modifications for crazy low end power on my H2O NC50

Like what?

Re: Modifications for crazy low end power on my H2O NC50

#CrazyWayne™ rocks. #CrazyWayne /

Re: Modifications for crazy low end power on my H2O NC50

Sweet express. I was wondering what kind of water pump did you use and is it a 12v? If it is how did you convert it from 6v?

Re: Modifications for crazy low end power on my H2O NC50

Rob GasketFace /

Thanks, I'd spiffed it up and added a VM18 since this post (see photo below).

I used this water pump:

http://www.treatland.tv/honda-camino-polini-water-pump-set-p/polini-water-pump-170.2040.htm

It runs off the flywheel, so no electricity needed. The mount in the setup above comes with a flywheel nut pulley and a mounting bracket that lines it up perfectly on the NC50 and presumbly the Hobbit as well. See photo below.

Re: Modifications for crazy low end power on my H2O NC50

Princess Rapunzel /

Rob GasketFace Wrote:

-------------------------------------------------------

oh that's raaad

Re: Modifications for crazy low end power on my H2O NC50

best gas tank ever

Re: Modifications for crazy low end power on my H2O NC50

so how is it with the VM rob?

Re: Modifications for crazy low end power on my H2O NC50

this looks really clean without all the plastics and junk

nice job

Re: Modifications for crazy low end power on my H2O NC50

What plastics lol? The bike only ever had an air box.

Re: Modifications for crazy low end power on my H2O NC50

i confused models.

Re: Modifications for crazy low end power on my H2O NC50

how do you start it? i can't tell what you have going on where the kickstart arm usually is. can you bumpstart an nc50? i know my urban won't.

Re: Modifications for crazy low end power on my H2O NC50

No you can't. And, it looks like a pulley for a rope start.. except it wouldn't spin all the way around. It's a 78 so perhaps you could just wind it fully with one pull.

Re: Modifications for crazy low end power on my H2O NC50

NX50 SWAP!!

I was stuck around 42 with the stock one speed engine

I also have a 15 15 sha. metal screen with a foam cover now and #68 jet

with the bx26 and the 10 inch rear wheel im around 45

and also it wheelies pretty damn good with the 10 and stock drive belt and top speed is around 40mph

I can do the whole block, when it hits the power band it pulls the front up without even trying!

a buddy of mine has this kit on a 2 speed express. it does 44.7 or sumthing

and talk to david cox! he has a lot of experience with these water cooled express's

swap.jpg

Re: Modifications for crazy low end power on my H2O NC50

Smaller rear wheel would do the trick. Lace up a 10 inch rim on that sucker.

Re: Modifications for crazy low end power on my H2O NC50

Rob GasketFace /

> so how is it with the VM rob?

scary! Still need to do some tuning, but I hit 48mph already.

> how do you start it?

It's pull start, but you have to do the kickstart conversion (Google it).

> NX50 SWAP!!

How easily does the motor mount up?

> Smaller rear wheel

I considered just getting a skinnier tire. This would be comparable to dropping a tooth or two on a sprocket. These tires might look cool:

http://www.treatland.tv/vee-rubber-VRM-329-gekko-star-GP-60-90-14-p/vee-rubber-vrm329-60-fslash-90-14.htm

Re: Modifications for crazy low end power on my H2O NC50

the swap was easy, like I said david cox and ryan offered up some helpful advice, it just bolts right on, no problems, you will need a different rear shock tho, I am running a tomos shock, works fine. also you'd need to wire the cdi up, you need the nx50 rear brake cabel and your wheels wont fit bc the brakes are bigger. you can use your stock brake cable if you keep your stock intake manifold (which you can) but the reeds arnt the same, I bought boysen ones for the nc50 and the nx50 ones were bigger and faced the opposite direction so I left them in their :/

Re: Modifications for crazy low end power on my H2O NC50

The whole reed block will swap back and forth though.

« Go to Topics — end of thread

Want to post in this forum? We'd love to have you join the discussion, but first:

Login or Create Account