www.zxrworld.co.uk

Does anyone know where I can buy a 47 bhp restrictor?

Or any mathematical geni' know the diameter hole I would need, Ill just machine some up.

Do you mean 33bhp?

Check the very top post of this forum

well if you know the drilled out central portion's diameter of a standard 30bhp restrictor you can work out its cross sectional area (ive never had any fitted so i dont know what that diameter is) ( radius = diameter/2, and pi x radius x radius = area of a circle).

say a standard bike is 60bhp, measure the cross sectional area of the rubber inlet and get that cross sectional area, lets say its radius 20mm.
measure a 30bhp restrictor and its radius is 10mm.

for example, if 60bhp = 1256 mm square, and 30bph = 314 mm square, then you need an area of ~ 720 mm square, square root of (720/pi) = necessary radius = ~15mm

but its all gonna be guestimation until you get it on a dyno...why 47bhp as well?

The new licensing laws as of January 19th 2013 restricts new riders to 47bhp from the age of 19-23 for two years (upon completion of mod 1 +2 on a 500cc 33-47bhp machine).

After those two years you have to take ANOTHER mod 1 +2 on a machine with a power output >47bhp to gain an unrestricted license.

It is a an absolute farce in line with EU legislation enacted this year.

Direct Access age limit has also been increased to 25.


So you are saying Power output is directly proportional to the effective surface area of the inlet manifold.

presuming the standard output is ~60bhp, 33bhp restriction approximately halve the intake manifold's surface area.

Therefore its just a case of simple ratio, reduce surface area of the inlet manifold opening by a factor of ~1/3 and that will do it.

i think its actually an exponential increase, so a small airhole in the 33bhp restrictors can give half of the power of the bigger bike with a much increased bore, ask around here, someone must have a set of restrictors, if they can measure the internal diameter of the hole you can plot that on a graph, plot 60bhp and the internal diameter of the carb inlets, say that a 0mm hole (i.e. a plate of metal) will give you 0bhp and plot that, im pretty sure it will be a curve...in any case it will give you an idea of what size plate to make, and you will always be best off taking it to a dyno place and getting a print-out for if the police stop you...

There is a thread around somewhere with the restricted diameter, I will throw a quick graph together as you say and take the calculated 44/45BHP mark just to be on the safe side, get it machined and dyno'd.

Its such a shame to have to restrict such a nice engine, kind of makes you want to break the law

I can't abide people who ride/drive without insurance, its totally reckless and can potentially ruin someones life, so if restriction keeps my insurance valid then so be it, it must be done

You are correct as always:

Exponential relationship with equation:

Hole Diameter = 3.442e^(0.0454*BHP)

I think this is the first time I have used relatively complex maths in a real world application, strange that.

Anyways, in theory 47BHP will require a hole of diameter of 29.0574mm, so call it 28mm to be on the safe side.

sounds good to me, i would still pay the £30 for a dynorun, it will tell you all you need to know.

plus it might reveal if you need to tweak your fuelling slightly as the restrictors might make the main jet too rich.

You can buy 47 HP restrictors online :

http://www.greybikes.no/side7.html

I sent email to him and can get them for kawasaki zxr 400 aswell..

The price quoted there is £337 (3250 Krona), that is in the simplest terms absolutely absurd!, it costs less than £20 to have them machined, now I have the parts accurately designed it is an absolute doddle to get them built and fit them yourself, no-one should be made to pay that sort of money for such a simple piece of engineering.

Talk about cornering the market :/

It is the only place i could find them.

Waow

Thank you very much for the link ..

I hope he can send them to Norway, says in description " may not send to Norway "

But its alot cheaper and i still get papers , and proof of the kit

Hi Guys, Im new to biking and was wondering if anyone has instructions on how to fit these restrictor kits?

Green Ninja wrote:Hi Guys, Im new to biking and was wondering if anyone has instructions on how to fit these restrictor kits?

remove rear panels, front vanity cover, fuel tap, fuel tank, airbox and carbs. the restrictor fits between the carb rubbers and the engine.