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jug5525 |
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jug5525 L Plate Warrior
Joined: 02 Apr 2021 Karma :
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Posted: 18:34 - 02 Apr 2021 Post subject: Weird throttle issue on a scooter |
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I have a 2 stroke Kymco agility 50cc scooter that i have recently upgraded with a 70cc malossi kit. I have also installed a racing exhaust and have increased the main jet size from 70 to 82.
After riding it for a while I have noticed a strange thing that happens when driving it on a straight at full speed and wide open throttle. If I release the throttle from wide open to about 90%, the scooter actually speeds up. Continuing to drive at that position for about 10 seconds caused it to suddenly cut out. The speeding up when slightly decreasing from full throttle seems to be happening quite consistently but only at top speed. Other than that I don't see any obvious problems.
Any idea what it could be?
I'm guessing it's carburetor related but not sure how to fix it |
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Easy-X |
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Easy-X Super Spammer
Joined: 08 Mar 2019 Karma :
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Posted: 18:55 - 02 Apr 2021 Post subject: |
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Sounds like overrun due to a lean condition. You've mentioned all sorts of... dubious upgrades but what did you do with the air intake? ____________________ Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter |
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Nobby the Bastard |
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Nobby the Bastard Harley Gaydar
Joined: 16 Aug 2013 Karma :
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jug5525 |
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jug5525 L Plate Warrior
Joined: 02 Apr 2021 Karma :
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Robby |
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Robby Dirty Old Man
Joined: 16 May 2002 Karma :
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jeffyjeff |
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jeffyjeff World Chat Champion
Joined: 02 May 2020 Karma :
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Easy-X |
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Easy-X Super Spammer
Joined: 08 Mar 2019 Karma :
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Posted: 12:22 - 03 Apr 2021 Post subject: |
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Not changing the airbox in any way makes the exhaust swap a little pointless - you've not got more air flowing in so you can't have more fumes flowing out! That being said I found cheeky barrel swap and de-restricted CDI gave a little more useful power down low. Got it up to 40mph. That was on a 4-stroke though but you get the idea.
Bear in mind I have a full licence, no L-plates, so going >28mph on a little scooter is perfectly fine. If you're 16 these sort of mods are 100% going to get you into trouble! You have been warned.
Thinking again on your problem I still wonder about an air leak. On full throttle, everything is fine but there's more air coming in than should be. You've "covered up" this problem with the up-jetting. Easing off drops the fuel but the air's still flowing as wherever the leak has opened up the vacuum pressure is still holding it open
Is crankshaft seals going a thing on scooters? How old is this Kymco? ____________________ Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter |
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Robby |
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Robby Dirty Old Man
Joined: 16 May 2002 Karma :
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Old Thread Alert!
The last post was made 2 years, 359 days ago. Instead of replying here, would creating a new thread be more useful? |
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