New toys

[BPT7594]

Upgrading my PCX engined scooter to 165cc, extremely high compression ratio with new kit. PCX150 cylinder head, which comes with 29mm intake / 23mm exhaust valves compared to 27/22 mm from stock 125, plus the matching variator to put those extra power to good use.
On the side, I have successfully replaced the fuel injection system with a simpler, old school carburetor. I know it's not everyone's cup of tea but it's mine so... Plus it's simpler than using a piggyback , I did not have good experience with piggyback controllers in the past to be honest.

Time for some pictures.

This is the stock Honda 29mm intake valve, I like to use stock valves since they're easy to order and will seal perfectly with stock seats.

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High dome piston to go with bigger valves and bigger combustion chamber on the PCX150 head. Static compression ratio of this kit should reach 13 : 1

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60mm "flat deck" cylinder. Experienced tuners will love the fact the water holes are bigger, deeper plus they're far away from the combustion chamber, which helps prevent blowing head gaskets.

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Manifold to use with a carburetor, without carburetor insulator.

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CR9 iridium spark plug to go with high compression ratio. Iridium is total nonsense, I have to pay more since my local shop does not supply nickel CR9.

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A shot of my carburetor setup. The blue thing is the insulator with clamps to hold the carb assembly to the manifold and engine. This is a genuine Keihin PE 28 made in Thailand. Jetting is 42 pilot 115 main with 2 turns of the air screw. Running a K&N 1280 with rain sock. Sorry for the dirt, just came back from a rain.

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[Richard]

Nice pictures aside.....how does it run/ perform?

[BPT7594]

I've got more than 3000km on this kit and I must say it's really a boost over the embarrassment that is the power output of the PCX125 specifically and the entire Honda eSP scooter range in general.

I used to get problems with running the air filter "naked" like that. Most notably during heavy rains. The air filter is pretty safe in that spot from the rain, but my wheel will spin and splatter water onto the underside of the u-box, that water and dirt will drip down to the naked air filter and saturate it => no air for the engine.

However, I paid a hefty 25$ for a K&N rain sock like in the picture and no problem ever since...

[ScooterAddict]

With the bigger cc kit, did you also change the Variator and weights? What about the rear clutch and spring? Does the 165cc kit, and if I use the stock 150cc head, (I have a 2013 PCX150) what kind of horsepower increase? Or just better mid range pull? I need more rideability power, I have plenty of topend, 74-75mph..

[Oyabun]

With the bigger cc kit, did you also change the Variator and weights? What about the rear clutch and spring? Does the 165cc kit, and if I use the stock 150cc head, (I have a 2013 PCX150) what kind of horsepower increase? Or just better mid range pull? I need more rideability power, I have plenty of topend, 74-75mph..

Higher CR gives higher efficiency and power across the power band. I'm assuming BPT has used an aftermarket cam as well, which depending on the profile can boost mid range too.
Increasing power will not increase top speed - without touching the gear ratios.
Unfortunately as far as I know dyno graphs are only available for the takegawa kits where you can see available power at different ranges but these are usually compared to the stock 125 engine.

[BPT7594]

With the bigger cc kit, did you also change the Variator and weights? What about the rear clutch and spring? Does the 165cc kit, and if I use the stock 150cc head, (I have a 2013 PCX150) what kind of horsepower increase? Or just better mid range pull? I need more rideability power, I have plenty of topend, 74-75mph..

Higher CR gives higher efficiency and power across the power band. I'm assuming BPT has used an aftermarket cam as well, which depending on the profile can boost mid range too.
Increasing power will not increase top speed - without touching the gear ratios.
Unfortunately as far as I know dyno graphs are only available for the takegawa kits where you can see available power at different ranges but these are usually compared to the stock 125 engine.

I use Yuminashi camshaft that comes with the kit + 2 special roller rocker arms to withstand the cam profile.
Top end will not increase too much. I'd say + 10kph is easy.
I use Yuminashi variator with 10gr rollers, as I don't understand the art of variator tuning too much, I left it for the guy knows better than me to decide.
I use stock torque spring. I changed torque springs in the past, testing etc to learn a hard lesson that the torque spring must match the profile of the 3 ramps on the rear pulley. So I'd keep my stock torque spring for now. My stock torque spring is a KZR spring which is effing puny in term of length and stiffness. But it works fine with Yuminashi variator + 10gr rollers.

Low, mid is improved greatly. I do 50mph cruising (sorry that's the speed limit in my country) with about 1/8 throttle opening. Plus the torque from the engine is insane. My friend crashed my bike once just because of the initial torque load .

[BPT7594]

With the bigger cc kit, did you also change the Variator and weights? What about the rear clutch and spring? Does the 165cc kit, and if I use the stock 150cc head, (I have a 2013 PCX150) what kind of horsepower increase? Or just better mid range pull? I need more rideability power, I have plenty of topend, 74-75mph..

Rideability power meaning ? If you mean low to mid torque output I'd say it's much better.

I have the same stock 150cc head as yours with 29/23 valves, and I must say it makes the bike feel more alive. You cannot understand the importance of using a stock 150cc cylinder head on a big bore kit. It's not about bigger valves, yes bigger valves are good but a stock 150 head has much more meat between the combustion chamber and the coolant holes than a 125 head. Using a 150 head with a good head gasket almost guarantees a 95% protection against head gasket blowing even at very high rpm. + you get 2mm more on the intake and 1mm more on the exhaust so top end is much better.

I don't think about horsepower too much really. I think more about torque, that's the real thing. Horsepower is just a made up number . Torque is what you'd feel when you twist the throttle.

However, having more torque at high rpm is essentially the job of a better camshaft , which I'm currently running but the police in my country won't let me go faster than 60mph so that's a damn shame.