Once you’ve completely removed the restrictions on your bike, the next thing people want to install is usually an Aprilia rs 125 big-bore kit. You can only get so much power out of an engine while keeping power in a usable rev range, for So increasing displacement is really the only option if you want to increase horsepower and torque (which translate to speed and acceleration).

It is often said that ‘there is no replacement for displacement’ and a big bore kit just makes your engine bigger. This allows more fuel and air to be burned inside the engine on each power stroke, giving you more torque (turning force on the crankshaft). Horsepower is a function of torque times engine speed, so if you can crank out more torque on your new engine and allow it to accelerate just as easily, you can squeeze a little more power out of your bike.

These power and torque increases are not free. The only currently available Aprilia RS 125 big-bore kit gives you an extra 25cc (turning your bike into an Aprilia RS 150). This doesn’t mean you’re going to outperform 600cc bikes and the kit isn’t cheap. Expect to pay at least £400.

To keep your bike legal, you’ll need to re-register and reinsure it (insurance companies don’t like big-bore kits or riders who install big-bore kits on their bikes…expect the worst). Maintenance costs will increase as your bike will require exotic parts for an engine rebuild and since your bike is no longer in stock your resale value will decrease.

Big bore kits can be had online and sometimes for a bit cheaper than usual on eBay. The kit is basically a new top end for your bike, so if you’ve had your bike rebuilt, installing the big-bore kit is a straightforward process.

If it is absolutely necessary to install a big bore kit on your bike, I suggest you bore the engine and run it until you need a rebuild. He rebuilds the engine as a 125 and sells the bike to move on to something bigger and better. You’ll be able to use your bike like an Aprilia RS 154 and enjoy the extra power and torque from its bigger engine, but you shouldn’t lose too much money by reselling it.