De-restricting a VFR400 NC30?

[racefactory]

All the jap market VFR's are restricted to 60hp and have 190kmh limiters on them.

I am not interested in the top speed restriction so much but would like to know how to derestrict the NC30 of the 60hp limiter.

Searching around on the internet I have only ended wading through crap of squids trying to derestrict the top speed limiter (come on, what is the point of going over 190!! It's about acceleration!) and therefore am finding it difficult to find anything out.

Does anyone know the procedure?

Is it a carbs/exhaust/cdi thing or something more like just a Cdi or wiring?

I think this is in the right section?

Also- another thing i'd like to know is why a 250 2 stroke feels so much faster than a 250 4 stroke when they are (for certain in my particular experience) BOTH restricted to 45HP as per the japanese law?? I don't see how this is possible but yet it seems the case... . The weight difference is not all that great. How is this? Is it something to do with the way dyno measurements are taken and top speed limiters? What i'm thinking is the dyno is taken in 6th gear right? So if both bikes have a 45hp limiter then they will both get that figure on the dyno but the 2 stroke will actually get there so much quicker realistically speaking.

One more question! I thought torque was relative to power. How can a 250 2 stroke produce nearly double the torque of a 250 4 stroke and the same torque as a 400 4 stroke but yet only have the same 45hp as the 4 stroke 250 and opposed to 60 on a 400.

Thanks in advance.

[imdying]

Also- another thing i'd like to know is why a 250 2 stroke feels so much faster than a 250 4 stroke when they are (for certain in my particular experience) BOTH restricted to 45HP as per the japanese law??That would be the superior torque curve of the 2 stroke.

One more question! I thought torque was relative to power. How can a 250 2 stroke produce nearly double the torque of a 250 4 stroke and the same torque as a 400 4 stroke but yet only have the same 45hp as the 4 stroke 250 and opposed to 60 on a 400.I'm not going to give you the answer... do some graphs, consider the formula for deriving hp from torque, and the answer will be quite clear.

[lostinflyz]

pretty certain they not limited to 60 bhp. ive got 60 at the back wheel of my race bike which means the motors making more. its kinda hard to limit something to a horsepower figure. all you could do is use restrictive jets (which they do) and a restriced airbox (which they do). You cant really measure horsepower on the fly (well not with the kit on the bike). The 59bhp limit is a japanese thing where engines werent allowed to make more than 59. so all said they made 59. same thing with cars. i think for a while all jap cars had tobe less than 200kw or 300 bhp or something. so all the car manufactures jsut kept saying they were only 200kw.

the speed limit is a very simple proceedure to get rid of as well. so no more limits. well only the one your license and wallet can afford.

[lostinflyz]

and dont forget that torque is more important over a range. as we use lots of revs the peaky nature of 2 smokers gives great peak torque but gotta see the big picture. If you run every where within a few grand of red line yee hah its good but that only happens on the track.

[more_fasterer]

To get more power out of the the VFR you need to do the same as any other four-stroke: improve the efficiency. It's not "restricted" per se, it's more tuned to output up to 60hp.

This means you've gotta follow the usual four-stroke tuning path... start by improving its ability to get the air/fuel in (HRC carbs & airbox), its ability to get the burnt gases out (full exhaust system) then fit a race CDI and loom for the extra ignition advance up top & higher rev limit.

There's heaps of info about it on www.400greybike.cc. Oh and the top-speed limiter does get annoying on the track

[mark247]

As above for the 60hp thing

For speed limiter, just take the circuit board out of the speedo and put it somewhere else like behind it. It's easy as.

[racefactory]

pretty certain they not limited to 60 bhp. ive got 60 at the back wheel of my race bike which means the motors making more. its kinda hard to limit something to a horsepower figure. all you could do is use restrictive jets (which they do) and a restriced airbox (which they do). You cant really measure horsepower on the fly (well not with the kit on the bike). The 59bhp limit is a japanese thing where engines werent allowed to make more than 59. so all said they made 59. same thing with cars. i think for a while all jap cars had tobe less than 200kw or 300 bhp or something. so all the car manufactures jsut kept saying they were only 200kw.

the speed limit is a very simple proceedure to get rid of as well. so no more limits. well only the one your license and wallet can afford.


what are the restrictions with the air box and how can you remove them/modify? how much power would it be robbing?

About the jap vehicles power- i thought they meant those figures at the wheel. I've seen a few figures for various bikes- they were all pretty close on those limits so im not sure how much they are lying.

[mark247]

what are the restrictions with the air box and how can you remove them/modify? how much power would it be robbing?

About the jap vehicles power- i thought they meant those figures at the wheel. I've seen a few figures for various bikes- they were all pretty close on those limits so im not sure how much they are lying.

Japanese hp figures are always hairy fairy as. E.G from what I have heard a 300hp Jap car is not has power as a 300hp European car. Dont know why.

If you wanted to get more power out of your bike you would have to rejet it, get a more high flowing airbox etc. My mate did this with his nc30 are after doing all the little things he was still only making 66hp.

If you want 70+hp you gotta do a fair bit of shit...

[lostinflyz]

the fast and dirty.

retune the bike after:

-cut the lip of the front of the airbox, take the snorkel outta it. Take a paper filter and cut the paper out and fit a washable foam filter centre.

-After all that you will need to open up the exhuast, more the merrier.

Then change out the jets and needles. should be able to get at least 60 at the rear wheel piece of piss doing that.

to go further you need to HRC the carbies (velocity stacks, air scoop ect.) and fit up a race CDI

alternatively a nc35 engine has more snot.

can do more but it starts costing lots of money. and lets face it you aint gonna notice a few hp much on the road. all itll give you is a smile that you made it grunty. If your gonna race it then 430 or 450 it. cause thats the way to make real gains.

[bismarck]

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Would it make any difference?

[racefactory]

Ok thanks for all that. Anyone had any experience with those cdi? I have heard there is an after market one for Nc30 that doesn't last long.

What do you mean open up the exhaust exactly?

What size main jet and needle do you reccommend?

[Zoolander]

I think you're wasting your time with this one. Just enjoy the NC30 for what it is, they're a great bike as standard. You'd spend a lot of cash for an extra few HP that would probably go pretty much unnoticed anyway. If you want more power buy a 600.

[lostinflyz]

most after market CDI units are just to delimit top speed. generally i wouldnt bother much with them. main thing is to adjust the timing at higher revs (or something like that), really i know bugger all about them so i wont comment much.

Jet size is determined by how good your airbox and exhaust turn out. stock is anywhere from 110 to 118 (size smaller is common on the front cylinders) race bikes can go up to 140 somethings.

by exhaust opening up i mean putting a can (road or race) that is free flowing. full exhausts (aka tyga) help exhuast flow to create more power.

Fundamentally an engine is limited by 3 things. The first is air it can get into itself, the next is the amount of fuel. These two need to be mixed to a perfect ratio for best running (thus the need for retuning to acheive the balance). Finally all the yummy air and petrol needs to get out via the exhaust. The ability of the exhaust to remove the air is a complex wee art with many crazy factors.

So basically increasing these things will help improve power one way or another. just remember that generally they are related to one another (i.e. more air needs,more fuel and the inverse)

Eventually once you can continually increase these features you will find the limits of the engine and need to increase its durability (i.e. cranks, pistons, conrods)

All this is predominantly for race bikes really. Its farking expensive to do much to get sizable gains in power. Best thing is to get a grunter bike. I will say however that a perfectly tuned (not just well tuned but perfect) NC30 is a hell of a lot better than most. If you can get the throttle to be nigh on instantaneous and everything to move perfect it will feel a lot faster (and will be). unfortunatly again to get a perfect running NC30 requires hours and hours of dyno tuning and balancing. which is realllllllyyy cheap!!

[racefactory]

interesting.

I might just try jetting and the air box some time.

I had the impression the NC30 was ''restricted'' by something like some 2 stroke bikes.... eg. deliberate exhaust restrictions, small venturis, rich jetting, cdi etc.

[lostinflyz]

interesting.

I might just try jetting and the air box some time.

I had the impression the NC30 was ''restricted'' by something like some 2 stroke bikes.... eg. deliberate exhaust restrictions, small venturis, rich jetting, cdi etc.

well it is but in slightly different ways. the exhaust is super restrictive on the stock bike. orginally the bike can with 110 jets all round which are way to small. was changed after orginaly 89 bikes to 115f/118r i think.The needles on them are super long (to lean it out) and the airbox is rather stupid.

Just be careful doing too much to a road bike. The airbox changes are for a race bike and if you go travelling through grit/gravel or a construction zone, stones and the like can easily end up in the airbox and rip up a bung airfilter. And then if you leave it out in the rain lets just say thats not a primo idea.