derestricting Derbis

[27yo kid]

Any suggestions on how to derestrict Derbi GPR50s

[binge]

My mate George has got a Derbi GPR50, Hes just put a race pipe on it and it was fooking rapid!
Not hes got a Full 75cc Metrakit, including clutch and all the other expensive crap. And its scarey now! He can keep up with the restricted Cagiva Mito 125!

Good luck mate..

Ben..

[Dr Nick]

[binge]

I dont know what BHP it is has got, but its really fast.
My speedfight will be up its arse up to about 60mph, but then his bike just takes off in 6th gear. And because hes had a race gear box fitted, the 6th gear is a very long gear, so it just keeps going and going!

[27yo kid]

So am I right in thinking that I can just get an aftermarket exhaust and bolt it on? (with proper gaskets etc!)

I'm shite at welding. Great at cutting, even when I'm "welding"!!!

I'm after things that I can do wihtout needing to be too mechanically minded.

(although I'll probably get someone to remove the restrictors!)

[binge]

Yeh, its 2 bolts at the maniford, Take your Expansion chamber off (maybe a couple of brackets to unbolt, Take the pipe system and silencer (end can) off. Then simply bolt on the new one.
No cuting, no welding. all you need is a socket set!
A friend paid £140 for a full Metrakit exhaust (including the expansion chamber!)
Its a 15 minute job mate.
Maybe a air filter would help, well, they dont make much affect but they dont half make the bike sound nice
I have a feeling that there may be a restriction inside the air box. If there is it will be a brass plate with a small hole in the middle of it, just take it out and throw it away. You may need to turn your idol down a tad if you do this, or your bike will be ticking over at like 7K.
Good luck mate!

[27yo kid]

Excellent!
Where do the carbon reeds go and what the hell are they all about???

[binge]

My speedfight has carbon reeds. Basically they go in between your carburettor and your cylinder (they are in the inlet manifold).
Im not exactly sure what they do but they have somthing to do with when the piston goes down, they open and allow petrol to be sucked into the cylinder, and as the piston comes up, they close up and stop blow back through the carb. (I think).
Not sure if they improve performance, doubt they will...

Ben

[philcxiv]

You could just remove the airbox and carb restrictors then just remove the restrictors from the exhaust with a drill you simply drill the rivets out then it should come out with some effort or take it to a garage. They could do it but then again they might not because it is illegal. It is cost effective because you wont need to pay money for a new exhaust and fitting. It shoud'nt take long, but other exhausts do make them sound quite nice but not anything like a 600 mind just a better tone of the usally waspy sound of two-strokes. good luck I dont think you get anything but standard airfilters for 50s if you do get performance filters let me know because it is something i will be buying when i get my RS2.
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[philcxiv] [lucky 14] "I only use the brakes so I can accelerate all over again"
bikepics | ratemybike

[RS1Banger]

The garage that sells a GPR should derestrict it if you ask as part of the sale of the bike (just say do this or else I won't buy it).
Depending on the year of the bike it will have a 14mm or 17.5mm carb fitted, this will have a large effect on your power output.
If you want to go nuts you can buy 80cc kits that, with a >21mm carb, big front sprocket and an exhaust will see about 80mph, if you wanna go bonkers you can get the kit racing tuned (it might not last long) and I've seen "mopeds" do 100mph.
Try www.derbi-club.com/forum ask them
also www.50cc.nl they sell everything
or www.two-stroke-addicts.freeserve.co.uk/mick/home.htm he makes race expansion chambers (£120) and race tunes cylinders(£80), he also does a lot of work with the moped race series www.mopedmayhem.com
Any reputable 2 stroke tuner will be able to do the same.
My Rieju RS1 does 75mph now, but that's because I've worn the piston ring, it will cost me £15 to fix and should then be back up to 85mph as it was before.
This is without port alterations to the 77cc kit, although it does have a 21mm carb, Yasuni exhaust (good), carbon reeds (for higher revs), reed stopper plate bent back, timing retarded slightly, stronger clutch springs, largest front sprocket.

[27yo kid]

OK, I took off the pipes from the engine to the expansion chamber, but couldnt find any restricting collar. At all!!!

Where should I be looking?
Is it between the expansion chamber and the silencer???

Also, (and this is gonna sound really bad!)
Where are the carbs on a bike? On a car I can find them no problem, but everything is just so tucked away!!!!!
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Ashes to ashes, dust to dust, if you don't ride it, it will turn to rust

[sickpup]

[27yo kid]

Its not illegal.
Its only illegal if the rider isnt qualified to ride the bike.

Its the same as getting a 2litre turbo and sticking it in a mini. Its no longer a small engine. Thing is though, with cars engine size doesnt matter!
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Ashes to ashes, dust to dust, if you don't ride it, it will turn to rust

[cagiva gezzer]

Most 50's that are derestriced are ridden by 16 year olds who are only allowed to ride a 'moped', so making it any faster than 30mph will be ilegal.

If you're allowed to ride a larger bike, its fine. The only issue then is declearing the modifications with your insurance company.
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"because one stroke isnt enough and four strokes waste two"