Damn guys, I can't increase my rpm count

Delta0413

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Feb 7, 2024
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Hello, it's me again. Damn guys, I can't increase my rpm count. My engine changes are as follows:

SkyHawk 70cc (G4)
-Porting, (I'm sure I did it properly)
-Oko carburetor, (I made the correct settings after long efforts)
-Reed Valve G2
-Windowed Piston
-36T Sprocket
-Stock Spark Plug
-Stock Head, (Good condition )

Top Speed = 63 km (39 mph)

No matter what I do, I can't go any faster. I widened my exhaust port a lot (left and right). The exhaust is stock but there is no muffler.
Please help me. I think my rev count is 6500-7000.
 
Hello, it's me again. Damn guys, I can't increase my rpm count. My engine changes are as follows:

SkyHawk 70cc (G4)
-Porting, (I'm sure I did it properly)
-Oko carburetor, (I made the correct settings after long efforts)
-Reed Valve G2
-Windowed Piston
-36T Sprocket
-Stock Spark Plug
-Stock Head, (Good condition )

Top Speed = 63 km (39 mph)

No matter what I do, I can't go any faster. I widened my exhaust port a lot (left and right). The exhaust is stock but there is no muffler.
Please help me. I think my rev count is 6500-7000.
(39.146385111×1,056×4.1×3.6)
÷(26×π)
_______________________________
7,469.9676197493

You may've reached your engine's peak performance. Weight reduction, improved aerodynamics, hub bearing systems, and tire selection may be your only options left to increase speed.

The most important aspect at this point is: How good are your brakes?
 
(39.146385111×1,056×4.1×3.6)
÷(26×π)
_________________________
7,469.9676197493
It's not just the RPM formula answer he wants Jerry...He believes he should be able to get even higher RPMs and increase his KPM/MPH.

He is not happy with the 39MPH on a bicycle.

I think he is getting about the best he is ever going to get out of a Skyhawk motor of only 70 or 80cc.
 
It's not just the RPM formula answer he wants Jerry...He believes he should be able to get even higher RPMs and increase his KPM/MPH.

He is not happy with the 39MPH on a bicycle.

I think he is getting about the best he is ever going to get out of a Skyhawk motor of only 70 or 80cc.
I added more to the answer.

With the stock 44t that comes with these kits on 26" tires, his engine would be turning 9130 rpm in order to do 39 mph.
 
Hello, it's me again. Damn guys, I can't increase my rpm count. My engine changes are as follows:

SkyHawk 70cc (G4)
-Porting, (I'm sure I did it properly)
-Oko carburetor, (I made the correct settings after long efforts)
-Reed Valve G2
-Windowed Piston
-36T Sprocket
-Stock Spark Plug
-Stock Head, (Good condition )

Top Speed = 63 km (39 mph)

No matter what I do, I can't go any faster. I widened my exhaust port a lot (left and right). The exhaust is stock but there is no muffler.
Please help me. I think my rev count is 6500-7000.
Why are you running a stock plug? Get an NGK-BR6HS. Maybe a better pipe would help too?
 
Why are you running a stock plug? Get an NGK-BR6HS. Maybe a better pipe would help too?
Those may help some but this engine would be turning over 9000 rpm if a 44t was being used on 26" wheels. This is around the max rpm these engines are capable of. The reason for the almost 7500 rpm with the 36t is due to the load increase.
 
Those may help some but this engine would be turning over 9000 rpm if a 44t was being used on 26" wheels. This is around the max rpm these engines are capable of. The reason for the almost 7500 rpm with the 36t is due to the load increase.
Dude, you are right, but my engine rotates at the same speed even at idle. It's like hitting a wall
 
If you want to know what your engine is actually doing get a tachometer. I recommend this one:

Small Engine Tachometer Hour Meter: Timorn Digital Inductive Waterproof Tiny Tach Meter & RPM Meter & HR Meter for Dirt Bike | Chainsaw | Lawn Mower | Generator Motorcycle Boat Marine Outboard https://a.co/d/fWEchRy
 
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