8650 rpm at 45!?

[vermiselle]

Hello,
On my Super 8 2013, 50cc with original air box without restriction and main jet #88.
I recently installed a Tecnigas NextR exhaust and a Polini variator with 6.9G rollers who came with.
I saw the first owner installed the red torque spring.
My top speed with this configuration is 73 km/h on GPS (45mph) and digital rpm I installed, indicates 8650 rpm!

Is it too high?

The Tecnigas at this rpm it's a very noisy and the original engine scream a lot for 50cc, i would not damage the engine!

I want to buy Polini torque spring +15% and 7.5G rollers.

Is it a good choice and do you think i will lose performance

Thank's.

[TBR125]

My four cycle Agility 125 runs at 8500 for most of my traveling. For a 2 cycle that rpm sounds absolutely normal. Let me check torque and power rpm specs though.

[TBR125]

Hold on a second, is it a 4 or 2 stroke?

[TBR125]

For the 2 stroke version:"The engine produces a maximum peak output power of 1.50 HP (1.1 kW) @ 6500 RPM and a maximum torque of 2.50 Nm (0.3 kgf-m or 1.8 ft. lbs) @ 4000 RPM. Kymco Super 8 50 2T Engine and Transmission Technical Data"

For the 4 stroke: "Maximum power - Output - 3.35 HP (2.4 kW) @ 7500 RPM" 


That is surprising as I thought the 2 stroke would be a faster engine for more power out of it's small displacement. My Agility 125 will rev to 11500 rpm on a down hill. That is why I got the tachometer. I had occasional valve float on downhills and saw that was the reason. I would try to keep the engine under 8500-9000 for continuous cruising. You will put additional stress and wear on the engine but that is the cost of performance. I've 13,000 on the clock and is running great.

For the four stroke The most powerful rpm is 7500. Above that and the power starts to drop, unless you install a higher flow filter to feed the upper rpms. That does require re-jetting the carb though.

Hope that helps.



 

[scooterfan]

For the 2 stroke version:"The engine produces a maximum peak output power of 1.50 HP (1.1 kW) @ 6500 RPM and a maximum torque of 2.50 Nm (0.3 kgf-m or 1.8 ft. lbs) @ 4000 RPM. Kymco Super 8 50 2T Engine and Transmission Technical Data"

For the 4 stroke: "Maximum power - Output - 3.35 HP (2.4 kW) @ 7500 RPM" 


That is surprising as I thought the 2 stroke would be a faster engine for more power out of it's small displacement. My Agility 125 will rev to 11500 rpm on a down hill. That is why I got the tachometer. I had occasional valve float on downhills and saw that was the reason. I would try to keep the engine under 8500-9000 for continuous cruising. You will put additional stress and wear on the engine but that is the cost of performance. I've 13,000 on the clock and is running great.

For the four stroke The most powerful rpm is 7500. Above that and the power starts to drop, unless you install a higher flow filter to feed the upper rpms. That does require re-jetting the carb though.

Hope that helps.



 

I would be very surprised if that specs about the 2 stoke engines are correct.
As far as I know 2 stroke engines generates about twice as much power - compared to similar size 4 stroke engines.

[vermiselle]

Hold on a second, is it a 4 or 2 stroke?

It's a 2 stroke!

[big blue]

I would think that the 2T engine would be fine at 8500 rpm. My 1963 Tohatsu Sport made 6.8 bhp at 10,800! For cruising the heavier weights might be a better choice though.

[TBR125]

One issue with kymco's engine designs is they have a bike designed for a specific power and if they use a 2 stroke it is not a performance increase but a smaller engine. 2 strokes get thier power from high rpm. 6500 rpm 2 stroke has very little power.