How dangerous is derestricting a geared two stroke 50cc?

[alexcarr1113]

Hi all, I’m Alex and this is my first post here. I’m turning 16 soon and will hopefully be getting a Rieju MRT 50 supermoto as my first bike. For a bit of context it’s got a liquid cooled 50cc two stroke engine with a 6 speed gearbox and is restricted in the exhaust.

I’ve spoken to my dad about potentially derestricting it once i’ve been on the bike for a while so that I can get more use out of it, and he is insistent that it will lead to the engine blowing up due to being able to rev it too high. However from what i’ve seen on youtube, there is no rev limit to begin with and derestriction actually makes the bike safer as you can hit the same speeds with lower revs.

Would somebody be able to explain which one (if either) of us is correct and if we’re both wrong then what is the correct answer?

Many thanks
Alex

p.s. for anyone planning on telling me how a 50cc isn’t worth it and to wait for a 125 please refrain as I’ve done plenty of my own research and this is the decision I have come to.

[weasley]

Did your research include licence and insurance implications? If you make it faster than 45 km/h (about 28 mph) then you can’t legally ride it at 16.

From a mechanical point of view, if an engine has truly been restricted to a certain speed or power, then derestricting it will simply put it back where it naturally should be. So long as the fuelling and cooling are ok, it should work better.

But think about the long term consequences of getting caught riding without a licence and having your insurance cancelled.
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[Sister Sledge]

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[BTTD]

If you derestrict it, it most likely won't blow up, but you will be a criminal yoof with no licence or insurance.

[alexcarr1113]

[grr666]

If you're going to break the law then you may as well fuck it off completely and get a fireblade instead of
a stupid faggio hairdryer. Same difference.
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[piazza]

If you wanna do it, do it. Ignore this lot - half them did the same thing.

[-]

Just have a quick look at the number of threads on here from people not familiar with 2 strokes, who've de-restricted or modified the engine and can't get it to run properly.

It will need more than just the pipe either de-restricting or changing for an aftermarket exhaust, you'll also need to up jet the carbs to match, or yes, you could well seize it. The problem with a 50 is they are ridden pretty much flat out anywhere, without jetting, it will be running too lean if you double or more the power from it.

Some also need a different CDI. There are other threads about de-restricting this bike a few posts down aren't there?

Most of us did the same, but the police didn't go around with rolling road units to nick 16 year old's on 50's when I was younger. They don't rest power, just speed. I had a DT50MX, which once with a 60cc kit, used to go through a piston kit once a month on average, I'd keep one on the garage window ledge at all times. I used to kill a ring or the piston so often, I got the process of changing the piston and rings down to 30 minutes on an air cooled 50cc bike.
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[Easy-X]

So you want to break the law... "everyone else is doing it!" yeah, okay.

Well at least aim low. Just derestrict it and little else. You could probably get >70mph out of it with exhaust/airbox/carb mods but why draw attention to yourself? Restriction is ~30mph, just aim for 40mph.

Don't brag about it to your mates, don't ride about like a dick with your new sense of power, keep your speed sensible. Only open it up on a quiet road with no one about...

Really? Is it worth all that bother?
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[Riejufixing]

[quote="alexcarr1113"]

[Pete.]

[alexcarr1113]

[dynax]

If you really have to be a fuckwit go to another country and be one, our roads are bad enough thank you very much.
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[Pete.]

[Polarbear]

I derestricted my daughters Gilera DNA because when i rode it it frightened the life out of me. Couldn't keep up with the traffic flow, bullied by car drivers, it was horrible.

That was just a case of playing with the variator (sp?) pulleys and probably increased the bike speed by about 8mph.

No kittens died. No SWAT teams shot her and I felt a lot better with her having a few mph extra for when she needed it.

Just do it. Some rules are meant to be broken.
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[dynax]

[Fizzoid]

[BTTD]

[McHattrick]

When my daughter turned 16 I bought her a Yamaha Jog scooter. Nearest petrol was next village, so I would take it there to fill up for her. I have never been so scared on a bike. 30mph with traffic queuing up to pass you is really scary, esp when part of route was dual carriageway.
My son turned 16 last year and I bought him a 2nd hand Rieju MRT 50, which the seller assured me was NOT de-restricted. I took it for MOT and had it at 45mph which was a reasonable speed (still with traffic trying to pass though). I was reliably informed (here on BCF) that it is defo de-restricted, but to be honest I am glad of that, because it makes it a much safer bike.
My son only rides around village. We never see plod here. It is perfect intro to biking. Be careful, be safe. I don't see a problem.
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[stevo as b4]

I'd run it in, get the first service done and then un-restrict it. Look at all the twist and go 50cc owners that ride around with obviously u-restricted peds with noisy race pipes.

The issue is more about the OP being a sensible and responsible road user (i.e. not racing in a pack of 6 noisy mopeds at 45-50mph in a 30mph town centre, or making too much noise or being a dick in traffic cutting up cars or aiming at pedestrians etc).

The fact that although no fucks are usually given if a 49cc machine is exceeding 30mph, its by technicality of the law illegal, just means that the OP should exercise a bit more sense and restraint knowing this, and if he is sensible and keeps out of trouble then I'm sure no one will care other than do good curtain twitcher types (like middle age BCF folks).

The other fact is that despite the old Tef style nonsense about construction and use regs for mopeds, well today's high end road and enduro style 50cc's are very different. They have in many cases better chassis and brakes than old 125's like AR's, RDLC's etc.

Oh and though the laws may still be different in Europe, (doubtful though) don't any of you self righteous easily offended types go to Italy and see the 50ish cc bikes they are riding round on, you won't like it one bit.

[Alpha9five]

[Easy-X]

[ThunderGuts]

What are the brakes like on a 50cc bike? Up to the challenge of stopping something going 50% faster than it's designed to be going? Remember the energy to dissipate with speed isn't linear; going from 28mph to 40mph will roughly double the energy needed to be dissipated. Go from 28mph to 60mph, and you're talking four times the energy to be dissipated.
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[chris_hu_cheng]

Personally I would wait a year... from my perspective that sounds sensible, however I know to a 16 year old a year might as well be a century.

I also know that riding my Mobylette 50v which reaches 30mph on a good day is dangerous, i do it on country lanes, single mostly, in the sun, mostly because apart from quiet residential roads I don't feel safe anywhere else. 125cc and 600cc (my other two options) much safer.

So being able to do an 'assertive' 30mph is safer imho, won't stop idiots doing dangerous overtakes but will stop the OAPS etc. giving it a go.

Speaking as a Dad, I know that Dads says shit sometimes just to make life easier or push you in a direction. Also who pays for all this? If you de-restrict take ownership, be sensible and deal with any outcomes maturely.

Don't be the stereotypical twat about it and if you were my child then all is good, other Dads are available however and whilst they are still paying for food and electricity for games consoles they tend to get a veto.