derestricting a 4 stroke 125

As some of you will know from my previous thread about which bike I should get - I'm looking at buying a 125 very soon and I'm basically trying to choose between a Honda NSR125, Honda CBR125 and the new Yamaha YZF125R.

I assumed that all of these bikes made about 15 bhp when restricted but when derestricted would make around 30 bhp. However, I read on a few sites that dereistrcting the Yamaha is a very bad idea as it can cause it to pretty much die within weeks.

Basically I want a 125 that I can ride on L plates (so limited to 15 bhp), then take my cat A test and have it derestricted and ride it at around 30bhp until I can get a bigger bike. If the CBR and YZF can never do get anything more than 15 bhp then they are pretty much out of the question... so anyone got any thoughts on whether or not this is the case?

EDIT: oh yeah and one other question - what sort of mileage is good or bad for a bike? I mean I'm looking at 2002/2003/2004 registered bikes so should I not get anything with over 10K on the clock or is it safe to get something up to 20K or what?

Thanks

Chris

I don't think you can derestrict a 4stroke 125 much, from previous threads, but I may be wrong.

To derestrict something it has to have been restricted in the first place. 2 Strokes have to be restricted to meet power output laws but 4 strokes don't, so that really is all they've got to give. You could take them apart and give them a damn good clean out, set valve clearnances might help. If you've feeling really imaginative i guess you could super charge one, but there's no restriction as such.

bummer...

looks like I'm going to have to try find an NSR 125 thats worth having then... they seem to be so rare compared to the other two types of bikes.

Anyone think this one is worth a look? Its odd that its done a lot less mileage than all of the others on autotrader but is cheaper:

http://search.autotrader.co.uk/es-uk/www/bikes/HONDA+NSR/Ne-2-4-7-8-27-64-104-133-146-236,N-117-239-4294959676-4294967221/advert.action?R=200841320856410&distance=92&postcode=dn33+2hu&channel=BIKES&make=HONDA&model=NSR&min_pr=&max_pr=&max_mileage=

EDIT: just this second got a reply from the guy selling it (i asked what kind of condition it was in)

The Bike is not immaculate but in very good condition, with a few minor scrtaches. It's currently SORN as my son is at Uni and we are just after a quick sale. It has no tax but we have just put it through an MOT so it has 12 months. Regards

This was the other one I was looking at:

http://search.autotrader.co.uk/es-uk/www/bikes/HONDA+NSR/Ne-2-4-7-8-27-64-104-133-146-236,N-117-239-4294959676-4294967221/advert.action?R=200839319673607&distance=86&postcode=dn33+2hu&channel=BIKES&make=HONDA&model=NSR&min_pr=&max_pr=&max_mileage=

but its done twice as many miles as the other and is more expensive...

Got a CBR125 myself and can get to 75 on a good day.. If that helps at all..

Thats it out the factory apart from a micron exaust

Got a CBR125 myself and can get to 75 on a good day.. If that helps at all..

Thats it out the factory apart from a micron exaust

Mines completely standard and is still refusing to go above 63mph even downhill with me curled up and tucked like a little wet sock.

thought they were ment to be sports bikes these CBR125's??

i had 83 out of my shadow 125 which is one of the 'slower' bikes in the 125 range

Forget derestricting it, just sell your 125 when you've passed, which I'm guessing would fetch at least £1000 and buy yourself a bigger bike. It'll be cheaper than derestricting a 125 and it'll be a whole lot faster. Theres plenty of fast sporty bikes from around a £1000 up, and there was an Srad 600 for £900 on here somewhere.

but the insurance on a bigger bike will be a hell of a lot more...

I'm sure when I'm 21 I'll want to just do my DAS and get a bigger bike anyway but this is just until then. I dont really want to be paying out the ear for insurance on something that I've got to have restricted to 33 bhp anyway

I would buy 15hp 125, pass test sell it and buy another bike.

you'll get almost what you paid, maybe even more, unless you damage it.

insurance for a derestricted bike will be as bad, maybe worse, than for a bigger bike anyway.

NSR's were good bikes!, it's going to cost you time and money now though!

dude, 250cc 4 stroke singles only make 30bhp on a good day, your 125 aint gonna make that power.

Time for a 2-stroke RANT

If you want 30HP either go for a 2 cylinder, 250cc 4-stroke. Will cost alot as there arent many out there and will be more expensive compared to a 2-stroke insurance wise.

Buy a NSR125, then you've already got yourself on the right track. If the engine is in good condition then with it being a Honda it will go forever without missing a beat.

2-strokes only make twice the power because they operate at twice the speed so you get lots of power but not so much torque. Also when your on a NSR you will be able to watch your mates on their CBR's dissappear into the distance behind you eating your blue smoke.

My RS125 would pull 70 at 8000rpm and go to 90mph top speed. But when fully derestricted you can put mahoosive sprockets on it and it will become an excellent bike to ride. You should be able to pull 70 with 5500rpm with the same sprockets I used.

OK, time for a look see!

2 Strokes can be good bikes, but thats the point can be and only if they are well looked after.

A well looked after good 2 stroke is the mutts nutts to ride, however a nail of a 2 stroke becomes an unridable heap that will frustrate and cost.

What to do, well it really is up to you but have a good look around, read lots and dig around lots of bike shops.

but if you look around you can get an imported 250 4-stroke 4 and some real nice ones to from ZZR250, CBR 250 to FZR 250 EXUP all of which can be restricted to 33bhp (they put out 33-45 bhp standard) and if anyone is in any doubt about the capabilities of such a bike just ask anyone who has ridden with willow (who has an FZR 250 EXUP as one of her bikes).

Cost wise you should be able to pick up a really good example for around £1000 - 1200.

If it was me, I would buy an old 125 to potter on and take your test on, then flog it on and invest in a good post test bike, you can do what you want to a 125 but you will always be limited by the laws of physics and the size of the bike, a 250 is twice as big and will deliver more torque and power by a factor of at least 2.5. I would even start to look at restricted 400s they have even more torque!

Oh and as for inusurance, spend a bit of time ringing round I bet you will spend as much if not more an a 2004 derestrcted 125 compared with a 33 bhp 1990 400 ! and I know which one will be more fun to ride. remember unsurance quotes can be strange so your best bet is to ring round pretending you have passed your test to see what the quotes are.

You can import BIKES!?!?

Japan I take it?

Tell me how!!! I want a Honda CBR250!! 45BHP inline four and revs to 20,000rpm. Its almost as powerful as a 2-stroke equivalent.

thanks akey, I think I'm going to have to do what you suggest and just get a 125 that I can practice on and take my test as soon as I can, then get a bigger bike and restrict it. Then when I take my DAS I dont have to buy a new bike I can just derestrict my existing one

having said that, I still think I'll go for a CBR125 or something like that instead of just a cheap as chips bandit. Like you guys said, if I look after it then I probably wont loose any money on it when I sell it after passing my test.

Now I just need to find somewhere to do my CBT!

Anyone know how I derestrict my Genata XRZ 125, I cant find anything online. I also have put a Lextek 51mm Hexagonal Exhaust (SP1) on it but it seems to of made no differenct to my top speed

Welcome..

It's not restricted in the first place, it's just a slow 125cc bike.

You can't de-restrict something that's not restricted!

I think I can add some useful info on this subject...

1) Indeed a 125cc will not have 30hp if you "derestrict" it, that was only the case with some powerful 125cc 2stroke bikes back in the days, like a Husqvarna 125 that had up to 35hp...

Still most 125cc bikes are restricted though I think, because they can't have anymore power than 15hp exactly, so that engine will always have a little more in it I assume. You won't get more out of it than a few hp tho, like 1-3 or so but even that is not bad for a (light) 125cc bike. Another, more open exhaust (or with silencer removed) will not really make a difference on a 125 bike I think, now I did that on my own bike and I don't feel a notable difference.

2) 4Stroke bikes are slower/less powerful than the older 2stroke bikes however there are some aftermarket parts, mainly cylinder kits that can make your 125cc 4stroke bike go real fast as well. Malossi and Daytona for example make 180cc cylinder kits for a lot of models that reach like 28bhp. It can be a good option/investment if your 125cc bike is pretty slow... Here you can find some info on supported models/bikes etc: https://www.malossistore.eu

I own a Fantic SM125, 2019 model and it's a very light and fast 125 bike by default, despite it having only 9.7kw instead of the max 11kw that most 125cc bikes have, which is the max allowed in that class. Another rule says you can't have more than 0.1hp/kg, and this bike is very light (96kg) so the power had to be limited. I'm having it derestricted now and I'm curious what the power output will be, I'm sure it will add some nice power since it's a powerful engine and already accelerates nicely.

3)

3) As for insurance I don't think you should let any bike purchase or interest depend on that, I used to think for a 125cc bike insurance is a lot cheaper too, but that's not really the case as I'm aware cuz you have a few added costs in insurance always, and for me a much bigger difference in cost is that to drive a 125cc bike here you don't need a moto driving license and a car driving license is sufficient. Also the price of a new bike, which I paid will be a lot lower than let's say a 600. But for these things it might still differ according to where you live...

For me personally this works out really well cuz I don't need a bike to drive highways at high speeds, I don't like that and these kind of bikes aren't made for it either (supermoto).

I think it's a waste of money than to buy a Husqvarna 700 for example (new) and spend A LOT more money on it, while you don't need all the extra power etc, +doing driving license which will cost another 1000-1500euros here.

Any questions I'll be glad to answer...

You could actually do quite a bit of work to gain performance and reliability but at cost due to the type of work and part's reworked and or replaced.

Valve,cam,crank, piston's,rods,clutch,carb/injection,bore.

You could Go on forever and if you do the mechanic's yourself, find a cheap enough machine shop capable of the machining???

You could actually do quite a bit of work to gain performance and reliability but at cost due to the type of work and part's reworked and or replaced.

Valve,cam,crank, piston's,rods,clutch,carb/injection,bore.

You could Go on forever and if you do the mechanic's yourself, find a cheap enough machine shop capable of the machining???

I like your ambition but you're living in fantasy land. No one is going to do that work on a 4 stroke 125 road bike unless they're completely bonkers

125cc bikes are built to suit the current A1 licence requirements, if you are licenced to ride a more powerful bike then rather than f**k about with a 125 ride something with more HP

The thread is 12 years old. I reckon the OP has probably moved on by now.

The thread is 12 years old. I reckon the OP has probably moved on by now.

If he's still on his 125 he won't have got far