125 Vs 200
 

Hi guys is there much difference between an ec125 and an ec200 ? What's the most I could bore my 125 to whilst keeping the reliability ?

I have owned both and still have a 125 as a spare bike. They both make similar peak power but the 200 has a lot more low end and midrange. The 125 weighs between 15 and 20lbs less than the 200 and you can feel that.

If you already own a 125 there are things you can do including a big bore kit to make more power. On my 125, I changed from the 38mm carb to a 35mm PWK carb (from an older kx125) and that helped the throttle response and it still revs to the moon. I cut the head to fix the squish and to increased the compression and that made a big difference in the bottom end and mid range. Even after those two changes the 200 still has more midrange and bottom end. I weigh 250lbs so I am not a typical 125 rider ;-)

All the local enduro races here tend to be won by 125's and 150's... But they're also ridden by spring chickens!

People here have bored out to 144cc. That's a quite common mod to many 125cc motors and I would assume quite well proven. Above that is unknown territory.