2 stroke power band kicking in way too late

[ukzzRider]

hi guys, posting on behalf of my brother,

he has a kymco super 9, 2 stroke 50cc moped.

All standard apart from a sports exhaust.

It was working all fine until he decided to tinker with his air to fuel mixture. Since he did that, the power band i think its called, kicks in really late.

It takes ages to get to 30/35, once he gets to that speed, the bike will throw you back a little cus the power kicks in.

I screwed the air/fuel screw all the way in, then out 1 & 3/4 times but has made literally no difference. not even made it worse.


I don't know what else to try, everything i do makes no difference.

Any help would be great! cheers for reading.
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[andy_uk]

Was it re-jetted when the new exhaust was fitted?
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Aprilia Classic 125, GS500E, ER5-A1, ER5-C4, ER6 & an XJ6 project frame...

[N cee thirty]

i fail to believe there's going to be a noticeable powerband on a 50cc scootay

Do a plug chop to get the mixture correct if its not the same as it was before fiddling.
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'00 Aprilia RS50 > '92 Honda CG > '99 Yamaha Fazer > '91 Yamaha RXS > '79 Suzuki X5 > 01' Honda Cg > 07' Honda Cg > 82' Kawasaki Z200 > suzuki gsxr 400 gk73a > honda vfr 400 NC30 Mod 2 Passed 09/06/2011

Jewlio Iglesias wrote: I actually did vote BNP once

[pdg]

It's probably just a coincidence that the powerband went slack or wore out at the same time he played with the carb.

The powerband either needs adjusting or replacing - probably best to check the subframe for straightness too as a slack powerband can twist it............















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Any and all advice given should not be followed - if you have to ask it means you don't know so get a man in to do it for you.

[Quornholio]

Marmalade stocks a variety of powerbands, so I believe?
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[smegballs]

Get the green one, a 50cc scooter is never gonna have much powah whatever band you get (not even with a red one!). You might as well get the band which gives best fuel economy and enjoy the scooter for what it is: a cheap commuter.

[Robby]

The mixture screw only affects the mixture at idle. To alter the mix further up the rev range, you need to mess about with jet sizes and needle height.

Assuming it ran ok on the new exhaust before he started messing with it, the problem is more likely to be down to worn out rollers or drive belt. Rollers come in a variety of different weights that give different characteristics, stick with the same weight that it currently has or you'll end up making more problems to chase down.

Don't expect to get any performance out of it, it's a Korean 50cc scooter. If it eventually gets up to 40 on the speedo, don't expect more.

[ukzzRider]

by the powerband, I mean a sudden burst of power. On my bike it does this at around 15mph. But on my brothers it does it around 35/40 mph.

Like i said, the only thing he has replaced is thee exhaust & it ran perfectly when he did this. Its only gone tits up since he tinkered with the air/fuel screw.

His bike will do 50+mph on everything standard apart from the exhaust which surprised me.

If he does need to change his jet, which size should he get? bigger or smaller?

Is there anyway I can reset the carb to standard? hopefully that should fix it.
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[pdg]

[ukzzRider]

okay let me rephrase, according to the sppedo it will do 50+ & thats in mph! big number are in kmp, little numbers are mph...

And sudden burst of power, like a gear change in a car, describing the best I can :L
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