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Pros and Cons of Common Modifications for Chinese and Japanese Scooters

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Big bore kits

In addition to a piston, rings, and a cylinder, most kits include the circlips and gaskets necessary for installation.

They are often a cost effective way of making your scooter go faster. I charge between $150 and $200 to install them, depending on the year, make, and model. Parts are between $60 and $200 for most scooters.

Pros

  • Your scooter will be faster. How much faster depends on the scooter.
  • For Chinese scooters, a big bore kit is often the difference between a scooter that is terrifying to operate on Colorado roads and a scooter that kind of sort of keeps up with traffic.
  • Some Japanese scooters pop wheelies and cruise along at 50 mph after a big bore kit is installed.
  • Installation is straightforward for scooters with 2 stroke (2T) engines.
  • Kits for Chinese scooters are inexpensive, plentiful, and reasonably well made.

Cons

  • Fuel economy will suffer. If you normally get 90mpg before installation, you may only get 60mpg afterwards.
  • Reliability and longevity will suffer. The stock piston and rings may have lasted 20,000 miles on your Kymco People, but it may only get a quarter or half of the way there after a big bore kit is installed.
  • Some mechanics claim you’ll get the same fuel economy, reliability, and longevity with a big bore kit as you will the stock parts. This is, pardon my language, horseshit. Bigger engines use more fuel than smaller engines, period. Their reciprocating parts are larger and put more stress on everything around them.
  • What these mechanics actually mean is you may not notice a reduction in fuel economy because the difference between 90mpg and 60mpg is negligible in terms of dollars spent putting gas in a scooter. You may not notice a reduction in longevity because you’ll probably stop using or sell your scooter before the new parts wear out.
  • Installation can be tricky on scooters with 4 stroke (4T) engines because of cam timing.
  • Kits for Japanese scooters sometimes cost $250+, not including installation.

Is a big bore kit worth it? For me, the answer to that question is usually “Yes!” because I’m willing to sacrifice a little fuel economy and reliability to ride a faster scooter.

Scooter transmissions

A transmission is a gear reduction device that takes power from an engine and delivers it to a vehicle’s drive wheels. Scooters use a belt driven constant velocity transmission (CVT). There are many upgrades available for scooter transmissions. Some of them are worth doing for certain reasons, and others aren’t worth doing at all.

Rollers & sliders

The little round, plastic cylinders inside your variator. Trying different weights and shapes changes how power is delivered from the engine to the rear wheel. Part prices vary. I charge $72.5 to tune and install them.

Pros

  • Inexpensive to purchase and install.
  • Potentially has a dramatic effect on either acceleration or top speed.

Con

  • What you gain in acceleration you lose in top speed. The reverse is also true.

Variators

The part that attached directly to the crank and functions as the front sprocket, gear, or pulley. It changes shape as the engine revs.

Pros

  • Aftermarket variators sometimes have a different ramp angle that causes them to change shape faster than stock variators as the engine revs increase.
  • They look nice.

Cons

  • More often than not, aftermarket variators are shiny, expensive versions of the stock part that don’t result in meaningful performance gains.
  • You can’t see them underneath the transmission cover. So it doesn’t matter how nice they look. My Honda uses a stock Kymco variator with 5.5g Dr. Pulley sliders in it.

Belts

The belt inside the transmission drives the clutch mechanism via the crankshaft. Without it, your scooter’s engine would rev up, but you wouldn’t be able to ride anywhere on it. Stock and aftermarket belts are available.

Pros

  • Aftermarket belts made by Gates are well made and inexpensive.
  • Easy to diagnose when it breaks.

Cons

  • Belt replacement does not result in performance gains. Belts are a maintenance item and should be looked after accordingly.
  • Though unlikely, significant engine damage may occur if the belt breaks.

Clutches

Some parts manufacturers and retailers claim that aftermarket clutches make your scooter faster. More often than not, similar gains can be made simply by swapping out the rollers in the variator for lighter or heavier sliders. There are no pros to these aftermarket clutches unless you like blowing money or fantasizing about installing pretty parts on your bike.

Alarms & radios 

I cannot recommend installing an alarm on your scooter. If you’ve already bought one, and you insist on having it installed, I’ll do it for you. But it’s not something I would encourage you to do. I would also encourage you to avoid installing any kind of radio or speakers on your scooter. Let’s talk about the pros and cons.

Pros

  • With respect to alarms, you benefit from a false sense of security. I’d rather you benefitted from vigilance and the security that only a hefty, frequently used lock provides.
  • Blasting down the open road with your tunes.

Cons

  • Nobody pays attention to alarms when they go off. If someone’s trying to steal your bike, nobody will stop them simply because it’s making a bunch of noise.
  • You aren’t going to be around to hear it going off anyway.
  • By the time your alarm stops, your battery will be dead.
  • The slightest thing sets alarms off. If it goes off, there’s a good chance it’ll still be sitting there when you return to it. Except the battery will be dead.