Upgrading Engine

My Scooter Guy, Joe, tells me I can upgrade my 125cc Kymco engine to a 150.

I could use the extra power as I regularly schlep my wife, and dogs around all the time.

He’s charging me 3,500. He assures me the new engine is new and that he is getting it from Kymco tomorrow. I assume he is going to do something with my working 125 engine. Sell it? Transfer it to an other scooter?

Any thoughts? Warnings or advice? :stuck_out_tongue:

What does he say he’s going to do ? Bore the engine out and put a 150 piston in it ? That alone won’t give you 150 performance. I dunno but you might break the crank or drive belt - I’d go to Jeremy at Bikefarm for advice on that one. Usually a bore out requires a new piston and sleeve, a carb adjustment (if not new carbs altogether), uprated crankshaft, and uprated drive chain. But 125 to 150 is such a small increase, really not worth it IMHO.

$3500NT for a new engine from Kymco and this includes installation?

This raises my WTF?!?!?! alarm. Go to bikefarm and talk to Jeremy as this sounds like a scam. I pretty damn sure that a new engine would cost you more than that and your bike is built for 125cc’s of power. 50cc bikes that are bored out to 90cc have a very short life(but are fast and powerful) before the next engine overhaul from what I’ve heard and you’re planning on something similiar

So like Taiwan Beer said:


I’ve heard that Jeremy is a pro. Maybe he’ll post here!
I live in Taoyuan so bringing the bike to TPE is not totally convenient.
I don’t want to shorten the life of the scooter. I want more power without having to buy an entirely new bike. Maybe I’m dreaming and it’s not possible without wrecking the bike.

Your bike will also be illegal…

The scooter’s engine casing has the ID stamp used on your registration.

I can’t see him replacing the entire engine for 3,500NT. I pay 4,000Nt just for a replacement head for my two-stroke 135. Most likely you’ll be getting a bore/larger piston. Then you’ll have possible overheating issues, and a shortened engine life from the hotter-running overbore.

The performance increase gained by doing this will be so slight it’s likely you won’t notice a difference…You can get a better performance increase by investigating gearbox upgrades/suspension mods/aftermarket exhaust/carburetor.

If your mechanic does indeed replace your entire motor, I would be highly suspect of the engines origin. Also ask him how he plans to change the ID number on your registration…

I’d give this a miss.

Locally made bikes have the VIN on the engine. It’s expected the frame will be bent and replaced, so they put the number on the engine. You cannot change the engine number on the registration. Ever. This will be a real hassle if you are stopped or get in a wreck, or try to sell the bike.
Many of the motorcycles and scooters here are produced in 125 and 150cc versions, so many times the parts are interchangeable. The difference in weight between the two pistons is very small so usually the whole bottom end of the motor is common, just the cylinder, piston/rings and head being different. The carb’s jets and needles may also be different. In this case, swapping all of these parts is very simple and won’t cause any problems or loss of reliability if the work is done well and all the required parts are swapped. As other posters point out, the difference won’t be huge. If I were you I’d make sure to keep hold of your original parts since you might need them later.
You’ll get a more noticeable improvement in performance by changing the rate at which the transmission’s drive ratio changes. That’s done simply by swapping small weights in the tranny which control the pulley diameters against engine speed, making the engine rev harder at any given speed. Ask your mechanic about this.
I do think you are simply postponing the inevitable however. If you have a girl and dogs to run around, you’re going to end up with four wheels sooner or later.

He won’t understand this, I dont! Maybe someone can translate this to Chiense?

[quote]I do think you are simply postponing the inevitable however. If you have a girl and dogs to run around, you’re going to end up with four wheels sooner or later.
Parking costs a fortune here. We usually rent a car/van for weekend trips. I want more power for my day-to-day travelling and weekend treks to the local hills.

Thanks everyone for the great advice so far. :rainbow:

Your KYMCO scooter has an automatic transmission, known as the CVT or Continuously Variable Transmission. Inside, behind the front belt pulley, is the “variator”, which has six metal cored plastic rollers that lay in a radial pattern nested in slanting ramps. These ramps allow the rollers to travel to the outside perimeter of the variator. The weight of these rollers is magnified by centrifugal force as the engine spins the pulley. The heavier they are, the further up the ramp they will roll.

As they move away from the center, the inner pulley half is forced inwards, causing the belt to ride higher in the pulley, increasing the gear ratio. Think of a mountain bike shifting automatically from the granny ring to the big ring… So, if you have lighter rollers, the belt stays closer to the center between the pulley halves as engine speed increases.

Lower ratios mean the engine is turning higher revs, which puts the engine in it’s power band, the rpm range where the most torque is produced, any time the scooter is being asked to accelerate. At cruise speeds everything should be as normal. Advantage is better acceleration. Disadvantage is slightly increased fuel consumption and engine wear.

Try this tutorial for what’s involved. I’m sure your mechanic will have fitted plenty of these kits and know exactly what to fit.

Went to the shop today. He had a small box. There was no engine it. The only English was on the box was Cylinder. It was a round thing with a little cylinder inside. Cost me 3500.
The scooter feels different, not as smooth. Might just be in my head.
Joe mentioned to me that driving slow for the first 100 km is a good thing. I’m an idiot, I was gunning it on the way home to “feel the difference of power”. Promise to take it easy from now on.

Perhaps the 150 piston head is concave to make the extra 25cc and he put in a 150 piston ?

Unless he adjusted the carb your mixture will still be for a 125. Perhaps he did. :ponder:

Thanks for the explanation and tutorial link.
I like the idea of better acceleration but not at cost of engine wear. I am hungry for power. Going up hills with weight on the bike.

Unless he adjusted the carb your mixture will still be for a 125. Perhaps he did. [/quote]
Let’s hope he did! I have no way of checking this myself do I? The shop itself is very professional. They’ve got all these tools I haven’t seen at other shops. I guess they are making enough money to by the gidgets and gadgets.

[quote=“hexuan”]Perhaps the 150 piston head is concave to make the extra 25cc and he put in a 150 piston ?

Unless he adjusted the carb your mixture will still be for a 125. Perhaps he did. :ponder:[/quote]

The displacement of an engine has nothing to do with the shape of the top of the piston or the shape of the combustion chamber…

Price seems about right. You can up-size an FZR for 6-10k but that’s because it is 2 cylinder. A two-stroker can get a new engine or a bigger engine for next to nothing (again I’m not talking about a whole engine just the cylinder and piston). To rebuild an RZR engine it’s like 1500 n.t. as with most two-stroke scooters. But if you want a bike with power…just get an NSR 150.

Just purely out of curiosity, what amount of increase in engine wear would there be, only slight? And what would one of these cost to buy and have a mechanic install?

After having one of these for a while, would anyone recommend against it?

Compared to what would be caused by running with a dirty air filter, not changing the oil at recommended intervals, using cheap oil etc? Insignificant.

I don’t know what the kits cost now, IIRC they were under NT$1000. Trying to get a quote from a shop with a real separation of parts and labor is futile. I don’t know what you should pay for a package deal, probably not more than NT$1500.

Thanks, I’ll check it out.