Slow stock muffler

[ScrappyScooter]

I bought a stock Y2K muffler on ebay to test how much quieter it might be over my LOUD Technigas (I got the Zuma with the Technigas installed).

The stock pipe has great torque.
It starts moving as soon as I give it gas. The Technigas has to "rev-up" before it'll move.
And the stock is much quieter.


My problem is, with the stock muffler my Zuma tops out at only 30mph.
There is no acceleration past 3/4 throttle.

Is normal for a 70cc with a stock pipe?

[speedy_scooter]

I'm guessing your rollers, carb, and clutch arent tuned now. I'd put the technigas back on and live with the noise.

[Zuma-Zuma]

There is more to this than swapping a pipe. You probably also have clutch springs and rollers that match the pipe. This must be swapped out as well. Otherwise its not an apples for apples comparison. If you want it quiet, then tune it with the quiet pipe. If you want it fast, keep the pipe. Either way, you'll be faster on the pipe. BTW, is it an RS or a NextR.

The Technigas pipe isn't even making power on the bottom. The stock pipe has its power on the bottom. Do you know if it has a carb, airbox, torque spring or any other mods besides the pipe??

[ScrappyScooter]

It's my usual scoot:
Metrakit 70cc
Malossi-variator, belt, reed, red torque spring
Polini clutch
Mikuni 20mm
stock airbox (vented)
RS pipe

Why no more acceleration after 3/4 throttle?
Whats interesting is that 3/4 throttle is the same 30 mph on the Tecnigas.
Maybe the stock muff won't let enough air thru to take atvantage of the larger carb diameter. Yea, thats it!

On a stock carb full throttle opening is probably the same as 3/4 opening on the 20mm Mikuni.

Which means there may be some jetting issue too.

Does any of this make sense?

[pinkymingeo]

With your setup and the Technigas you should do 30mph at about 1/8-1/4 throttle.

[ScrappyScooter]

I think mabey i could spend more time jetting.
The plug looks good now, so I'm afraid of melting it if I start platying with smaller jets.

[Zuma-Zuma]

Maybe you clutched out too early? Meaning, the torque driver is fully open, vario fully closed, and not enough power to pull it? It sounds like a "torque stall". Load in excess of power. Maybe just adjust to keep the scoot in the power band. Do you recall the rpm's, or if its revving hi or low when its at 3/4 throttle.

[ScrappyScooter]

It seems to be revving hi.
The way to change this would be to use lighter rollers?
The rollers I have are not marked, but I think they are the 4g that came with the vario.

Is there another adjustment?

[XPS1210]

it revs higher then the stock pipe as it's called an expansion chamber... and it's supposed to do that...

Your scooter should be doing about 50 mph... and 30 with less then 1/2 the throttle...

with the stock pipe, you would need to change the roller weights and clutch springs to match the pipe...

Scooter parts are not plug and play... they MUST be tuned!

[Zuma-Zuma]

We can help you tune, you must choose a pipe. As jered, speedy, and others have said, you can't just swap 1 part for comparison. They all work together. If you run the stock pipe, put the stock springs back in. Maybe the stock trq spring and clutch springs. You WILL NOT have a hi revving scoot with stock exhaust. So the springs are a mute point, and you won't be in the powerband.