After drilling a hole in the piston, my engine now revs less.

Delta0413

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Feb 7, 2024
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After drilling a hole in the piston, my engine now revs less.
I use NT carburetor. A hole in my piston. I tried both possibilities. With and without holes. I turned more rpm without the hole. After the hole was drilled, the rpm dropped. and the smoke increased. I thought it had something to do with the carburetor. I bought and installed OKO PWK. But unfortunately the problem is the same. It chokes at the last throttle and the revs do not increase as before. I use a G2 reed valve. Are full gas mixtures rich or lean? Main jet 115. Pilot jet 38.

What matters to me is top speed
 
After drilling a hole in the piston, my engine now revs less.
I use NT carburetor. A hole in my piston. I tried both possibilities. With and without holes. I turned more rpm without the hole. After the hole was drilled, the rpm dropped. and the smoke increased. I thought it had something to do with the carburetor. I bought and installed OKO PWK. But unfortunately the problem is the same. It chokes at the last throttle and the revs do not increase as before. I use a G2 reed valve. Are full gas mixtures rich or lean? Main jet 115. Pilot jet 38.

What matters to me is top speed
What kind of brakes do you have?
 
After drilling a hole in the piston, my engine now revs less.
I use NT carburetor. A hole in my piston. I tried both possibilities. With and without holes. I turned more rpm without the hole. After the hole was drilled, the rpm dropped. and the smoke increased. I thought it had something to do with the carburetor. I bought and installed OKO PWK. But unfortunately the problem is the same. It chokes at the last throttle and the revs do not increase as before. I use a G2 reed valve. Are full gas mixtures rich or lean? Main jet 115. Pilot jet 38.

What matters to me is top speed
Had the same issue as you. I drilled a 12mm hole in the centre of my piston, installed a G2 reed valve and a PWK 21mm carb. I tried the stock jets and had the same bogging issue. I then changed out the pilot for a 32 jet and main 85. Then the bike ran good but i settled on a 88 main.
You can get main jets on aliexpress (5 euros for a pack of 10 from your choosing, take the smallest set or what i got 80-102)
Best of luck!
 
Had the same issue as you. I drilled a 12mm hole in the centre of my piston, installed a G2 reed valve and a PWK 21mm carb. I tried the stock jets and had the same bogging issue. I then changed out the pilot for a 32 jet and main 85. Then the bike ran good but i settled on a 88 main.
You can get main jets on aliexpress (5 euros for a pack of 10 from your choosing, take the smallest set or what i got 80-102)
Best of luck!
Thanks for the message. I changed the needle setting. Better now. But I'm still not satisfied. I would like to try what you said. But here's the problem. I live in Turkey and extra jets are expensive for me. In your country the product is $5. But if I want to buy from Aliexpress, tax + shipping + product = 400 Turkish Liras :) . I'll try something though.
 
Thanks for the message. I changed the needle setting. Better now. But I'm still not satisfied. I would like to try what you said. But here's the problem. I live in Turkey and extra jets are expensive for me. In your country the product is $5. But if I want to buy from Aliexpress, tax + shipping + product = 400 Turkish Liras :) . I'll try something though.
If you can get your hands on a set of mini drill bits, you can solder up the stock one and redrill it smaller.
 
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