NU50 Custom 26mm Intake Build

Building a custom intake to mount my new mikuni vm26 to on my NU50...pics to come with progress tomorrow.

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Re: NU50 Custom 26mm Intake Build

Charles Cole (OFMC) /

All you're gunna do is waste a bunch of gas and have poor throttle response.

Re: NU50 Custom 26mm Intake Build

those are some lungs; what kinda kit are you thinkin of running?

Re: NU50 Custom 26mm Intake Build

David Cox /

Its my same bike i have been running, full max modded urban with a malossi 47mm water cooled kit, just going from a vm20 to a vm26...some 2 stroke guru we talked with said our carbs arent big enough. Theres only one way to find out. If it sux i will just put it back.

Re: NU50 Custom 26mm Intake Build

Joe Schuitema /

I've got a hobbit with a malossi mhr replica 70cc. I'm bumping up from a vm20 to a tm24 and hoping to see a positive difference. In the spring I can dyno it before and after to see where the gains will be. I measured the vforce reedblock hole size and it seems like the limit is a 26mm. What reeds are you running?

Re: NU50 Custom 26mm Intake Build

I mean it's not crazy, but i'd warn against taking and applying advice directly from a 2 stroke guru if they're not a moped guru.

Specifically dirt bike guys, alot of the same stuff definitely applies, but alot doesnt, one of the big ones being the lack of gears, which can change alot about where you're running and where/how wide you wanna make power. at least you're variated though, so as long as you know what youre doing there you can take advantage of peakier high RPM power with a loss at low RPM.

for example, you look at an RM 80 and theyre running 28mm carbs, some of the competition folks run up to 32 and over. That's like racing dirtbike shit tho, those things make at least twice the power your kit does. and theyre spinning up to 14k, not to mention being slightly bigger too

the other thing to consider about carbs, and its obvious but also easy to overlook is that youre reading a diameter but the flow's gonna be proportional to the xsectional area, essentiall it scales with r^2. so like from a 18 to a 28 is 1.5x diameter but effectively 2.5x the size... that also affects your velocity. you've got a flow rate based on your engine's volume (draw per revolution) and RPM. so for the same RPM you have to have the same flow and so your velocity's necessarily gotta be smaller which can hurt the mixing of the charge and response. Flat slide might be better here also.

or the tl:dr w less theory, similar sized high performing engines can use that size range of carbs, but you might be overcarbed for the limitations of the cylinder and engine, and see worse performance in terms of responsiveness and low end torque.

and of course much worse gas mileage.

Re: NU50 Custom 26mm Intake Build

but yea, it will probably help at high rpm which oughtta be rad, and props for making it happen. I think joe makes a good point that the difference you didnt see with the bigger reeds before might become more apparent with the larger carb and as you push power to higher RPM

Re: NU50 Custom 26mm Intake Build

David Cox /

Currently gonna try these in the pic on the right below. U can see i have modded and opened up the cage alot compared to the left ones i was running and removed the bridge for more open area. I have a kx65 cage coming which i will prolly use with 4 petals aiming down, and try my brothers vforce setup as well for a a full detailed comparison on all three. Reason i went with vm26 is that air filter mount is same as vm20 i was using, and with our custom airbox setups that are a absolute must it was simpler. As far as rpm, this bike only makes power at extremely high rpm anyway with porting and such, output is adjusted with clutch and variator and belts so it never uses low rpms anyway. It pulls super hard anyway, just trying maximize things. I am bored as fuck.

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Re: NU50 Custom 26mm Intake Build

Biggest I've run was a tm24 and I wound up dropping back to a 15, trade away alotta high end performance that way, but it sucked filling the gas tank every ride

but if you dont try it youll never know. and not knowing sounds like the worst possible outcome of all those issues mentioned.

Re: NU50 Custom 26mm Intake Build

So , ignorance isn't bliss ? lol

Re: NU50 Custom 26mm Intake Build

David Cox /

My brothers na/nx combo is almost 20 lbs lighter than my nu rig. He can just edge me out by the smallest of margins, looking to dust his ass.

Re: NU50 Custom 26mm Intake Build

> Born to be WillD Wrote:

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

> I mean it's not crazy, but i'd warn against taking and applying advice

> directly from a 2 stroke guru if they're not a moped guru.

>

> Specifically dirt bike guys, alot of the same stuff definitely applies,

> but alot doesnt, one of the big ones being the lack of gears, which can

> change alot about where you're running and where/how wide you wanna make

> power. at least you're variated though, so as long as you know what

> youre doing there you can take advantage of peakier high RPM power with

> a loss at low RPM.

>

> for example, you look at an RM 80 and theyre running 28mm carbs, some of

> the competition folks run up to 32 and over. That's like racing dirtbike

> shit tho, those things make at least twice the power your kit does. and

> theyre spinning up to 14k, not to mention being slightly bigger too

>

> the other thing to consider about carbs, and its obvious but also easy

> to overlook is that youre reading a diameter but the flow's gonna be

> proportional to the xsectional area, essentiall it scales with r^2. so

> like from a 18 to a 28 is 1.5x diameter but effectively 2.5x the size...

> that also affects your velocity. you've got a flow rate based on your

> engine's volume (draw per revolution) and RPM. so for the same RPM you

> have to have the same flow and so your velocity's necessarily gotta be

> smaller which can hurt the mixing of the charge and response. Flat slide

> might be better here also.

>

> or the tl:dr w less theory, similar sized high performing engines can

> use that size range of carbs, but you might be overcarbed for the

> limitations of the cylinder and engine, and see worse performance in

> terms of responsiveness and low end torque.

>

> and of course much worse gas mileage.

Amen to that. Velocity is important and with gears you can get that by keeping it in the red. You're going to need a fat needle to compensate at low rpm.

Re: NU50 Custom 26mm Intake Build

Captain Janeway /

Make sure you post it when you're done. Are you going to race it? Seems like top speed would be in the 60s, but that poor little frame would have a hard time with it. I've seen one of your builds though (the one with the huge air box). That one looks like it could handle it.

I turned my oil reservoir into a backup gas tank because I'm sick enough of ongoing fill ups just on my 16 mm.

Good luck!

Re: NU50 Custom 26mm Intake Build

Jack Rutherford /

subscribed

Re: NU50 Custom 26mm Intake Build

David Cox /

That is same build, tuning carb now

Re: NU50 Custom 26mm Intake Build

David Cox /

My custom 35mm spigot intake and vm26 and the tried and true mlm vm20 setup...think a bigger cc motor will be needed maximize its potential. Got it running good but there isnt much difference so far. Still messing with reeds and jetting tho.

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Re: NU50 Custom 26mm Intake Build

David Cox /

Got some great updates: i was having issues on the urban so we put the intake and carb on dereks na50/nx50 combo with his vforce reeds and all we can say is FUCK! His bike will tear your head off in acceleration, its at least 30% improvement over the vm22 carb and intake we made for that. Wheelies are i big issue now..top speed is bout the same but that is fine cuz since his bike broke in half we aint concerned with going over 60 anymore...bottom line is this is funnest bike we have ever been on now. In the vm26 the stock 190 main jet was perfect, idle jet had to double in size to 50ish range, middle setting on needle was great. Plus cruising at 40mph variated in overdrive this thing is as quiet as a stocker with these airboxes even with h95 pipe. Throttle into and it makes some noise tho.

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Re: NU50 Custom 26mm Intake Build

looks nice, you work quick. what's your welder, just curious.

Clear tubing you can see the buildup, kinda surprised me how much gets caught in the dead zone between the two ends. ended up putting in a proper sized ring to couple em up nicer. doubt it matters much but it is neat to check out gas pooling in the eddies just from that little disturbance

Re: NU50 Custom 26mm Intake Build

i also wonder if your performance gains aren't just the new carb having better tuned low and needle, rather than gains from the actual size of the carb. Not criticizing but I worry that folks might read this and come away thinking "hey if I put a bigger carb on I get 30% more acceleration"... especially if the reality would intead bebetter said "hey if i have a better tuned carb I could realize 30% better acceleration than my current setup lets me experience"

sounds rad. i wanna ride it. blaster NX50s = awesome

Re: NU50 Custom 26mm Intake Build

David Cox /

Just put the setup on my urban, ran perfect but no stronger than the vm20 setup...the bike us alot heavier than dereks and it all just works for his rig, thats where it will go for good...well, now that i cant compete with his light setup at all, i wish i had bought a peoples pipe and had more of a reasonable setup on my urban. The welder is just a lincoln 115v 140 amp mig welder...wish it was a tig.

Re: NU50 Custom 26mm Intake Build

David Cox /

Ur right puttin a bigger intake and carb wont garantee any results on a particular bike as it didnt on mine, however, worked better than expected on dereks...my bikes just a big ole lazy urban compared to dereks, i am officially miserable.

Re: NU50 Custom 26mm Intake Build

I agree, 99% wont see the gains i did. It just worked extremely well for my setup. The vm22 was tuned to almost perfection, but the intake on the vm22 wasnt what this is. Not a smooth mandrel bend. We will make a smooth bent intake like this for the vm 22 and put it on the urban for good.

Man that vm26 rips on my bike, fuck!

Re: NU50 Custom 26mm Intake Build

Jack Rutherford /

Well, now you know.

Re: NU50 Custom 26mm Intake Build

David Cox /

I gots to know...lol!

Re: NU50 Custom 26mm Intake Build

- Summerai - Drew /

Let's see that airbox.

Re: NU50 Custom 26mm Intake Build

David Cox /

Circled for ya.

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Re: NU50 Custom 26mm Intake Build

David Cox /

Well, another day of testing, and we need to say, even tho dereks bike rips hard with the vm26 combination, driveabilty just isnt what it was with the smaller carbs overall. In conclusion, there is a reason alot of vm20 intakes r made...use our testing and wasted motherfuckin money as a free lesson learned and stay with bolt options from treatland, which includes case matching, not worth the trouble unless its an all out race bike. This is the bros signin out on this thread. Lets let it die. (edited)

Re: NU50 Custom 26mm Intake Build

Jack Rutherford /

Since we are signing out, you can't have part 1 without the other. So "gots to know" part II. I never noticed before how Eastwood and the crazy guy resembled each other in this almost final scene. Could be a comment on how not different they were, you decide.

Re: NU50 Custom 26mm Intake Build

> David Cox Wrote:

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

> Well, another day of testing, and we need to say, even tho dereks bike

> rips hard with the vm26 combination, driveabilty just isnt what it was

> with the smaller carbs overall.

Might be helpful to explain specifically what you mean. I would expect some pep until you get the needle up, then a flat spot until you're on the main. But that's just a guess.

Re: NU50 Custom 26mm Intake Build

> frank dadog Wrote:

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

> > David Cox Wrote:

>

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

>

> > Well, another day of testing, and we need to say, even tho dereks bike

>

> > rips hard with the vm26 combination, driveabilty just isnt what it was

>

> > with the smaller carbs overall.

>

> Might be helpful to explain specifically what you mean. I would expect

> some pep until you get the needle up, then a flat spot until you're on

> the main. But that's just a guess.

Actually, it was a flat ripper from take off to top speed, as long as u r final shift was at maximum rpm, it would pull like crazy, any lower and it would bog when notched variator went fully out. Off the line was excellent, lean forward or it might flip. But after it broke in half i am just not comfortable at those speeds on this bike anymore. So driving midrange and cruising it was peaky and not as smooth as the 20mm. Yes, jetting was spot on. All in all i drive in town and going block to block that fast wasnt as much fun as i thought. The variator weights had to be stupid light, revved to the moon all the time. For racing its great, for in town driving it sucked. The vm22 was real good too. But i will prolly run the 20mm carb and new kit (just purchased last nite from treats) not case matched. Once we did the case matching rpm range went up. David put a new new H20 kit on bone stock yesterday with vm20 and torque was much better, it didnt lose speed on final shift if it wasnt revved to the moon. Just want a good in town 55mph driver, if i need extreme power thats what the bottle is for. We wasted alot if money but learned alot too, and we werent bored. Next chapter, Serious Baddassery 2!, details later

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