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May 13

Posts: 2

kyleww95 says:

Restriction help?

I dont know too much about engine performance. I'm looking to buy a 600(ish) bike to last me two years, but heard that restrictor kit's can cause certain engines to perform badly, even degrade. When looking to buy, is there anything I should completely avoid if im wanting to restrict to 47hp?  Thanks for reading.  :D

P.S - Sorry if im spouting total rubbish :mellow:

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  • Posted 2 years ago (21 May 2013 00:30)

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Apr 08

Posts: 3042

AdieR says:

Not looked

into the 47bhp limit much, but with the old 33bhp limit, the general consensus was that twin-cylinder bikes (Kawasaki ER6 / Suzuki SV650 / Honda CB500 amongst others) were better candidates for restriction than 4-cylinder machines.

The twins make power lower down (restriction lops some top-end performance that you'll seldom use on the road), whereas 4-cylinder bikes tend to be "strangled" by restriction.


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Apr 13

Posts: 13

eitematt says:


I'd actually go against a lot of what people say on this from my own personal experience - i think a lot of the comments of people saying the bikes will be sluggish/suffocated etc perhaps come from people who have already ridden unrestricted machines as yes in comparison obviously the top end acceleration is majorly reduced - but if you're a new rider you aren't going to notice it.

I went from riding scooters, to a 125, to a 636cc ZX6R [restricted to 33bhp at that point also] over 5-6 years. At no point did the ZX6 ever perform badly or seem at all slow it was pretty bloody fast id say actually:biggrin:

Also, unless you go out riding it with a wheelie-popping hooligan attitude/death-wish, i'd say its actually a very good way to learn on bigger bikes, perhaps even more so than using a 400-500cc bike as a stepping stone, as i found by the time i unrestricted the ZX6 2 years later i was so comfortable with the feel and position etc it made riding it unrestricted come very naturally and quickly without any of the hair-raising moments.

I mean if you're going to absolutely hammer the life out of it when its restricted perhaps that may cause some engine wear, but i used to ride at motorway speeds and everything below regularly doing over 10k during the restriction and its been serviced by garages and myself since now at nearly 20k and you wouldn't know its been restricted due to any wear n tear. I even think it might of made it 'break in' easier having it restricted to be honest as it wasnt stretched much for a long time but that might just be me :lol:.

I should add [not that technically knowledgeable myself either but it may be relevant] the method of restriction I used was the FI international kit which was a throttle limiter pin combined with inlet-limiters that restrict the fuel/air. Unless its changed now, at that time it around 150 quid as although the parts and kit are ridiculously overpriced you basically pay for the certificate that comes with it that the installing approved mechanic signs to verify the bikes restricted. And don't be tempted to remove the restriction before you're legally allowed to as many people do as you may get away with it but if you have an accident/get inspected you are royally F'ed:doubt: friend of mine learnt the hard way, lost his bike, insurance didn't pay out and got a hefty legal bill from the other party in the accident.

Just my opinions anyway i'm sure many will totally disagree but personally i wouldnt worry too much about what you restrict just pick a bike you like and ideally maybe will continue wanting and using after your restriction ends.

Good luck:smile

[This Reply has been modified by the Author]

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Mar 11

Posts: 168

tc330 says:

Well spoken

Nice reply eitematt, good 1st person experience of riding restricted bike and good advice about sticking to legal requirements. :biggrin:

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Aug 02

Posts: 3270

eatcs01 says:


You can not restrict ANY bike to 47bhp. It has to be one that makes less than (IIRC) 95bhp* as standard.

*I can't remember the exact figure, so check it yourself via a training school. Basically, it rules out most 600cc inline 4s..

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May 13

Posts: 2

kyleww95 says:

Thanks! (Sorry for the wait)

I totally agree with the 'stepping stones' progression with engine size, but I'm 18 and just can't afford to buy a new bike every 2 years :,(.  I'm looking at a 2012 er-6f, a bike apparently very easy to learn on, not being too harsh on mistakes, but also being a very enjoyable bike for very experienced riders. It produces around 75hp, so can be restricted.  Also the restriction is something I wouldn't want to remove, I would like to use the 33hp as a 'stepping stone' for the 2 years before trying to utilise ALL the power...

Thanks for your response!

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