Backfiring

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BikeProblems

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Hi there,
I recently purchased a 66cc engine and mounted it to a bike. A couple of days ago, the engine started to backfire when i was reaching close to full throttle. It also felt like it was loosing power. i took a closer look and i think the fuel is com busting in the carburetor.
Does anyone know how to solve this problem.

Thanks.
 
Clogged exhaust, too lean a fuel mix? I dunno, got any pics supporting why you think it's combusting in the intake manifold?

I would guess that you need to adjust your throttle - you're just putting too much gas through the engine, causing it to bog down, and the backfiring is from unburnt fuel in your exhaust igniting.

Adjust the slide needle, adjust the idle screw, and adjust the throttle cable tension - all to decrease the amount of fuel flow, don't set it to increase or your problems will get worse/more common.
 
I think it is combusting in the carburetor because it goes bang and then there is smoke from the carbi all the way down through the inlet manifold to the cylinder.
Also does lean mean that it is running with to much oil, or not enough.

Thanks for the advice though, will try
 
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I honestly don't think you're backfiring out the carb, or else there'd be a melted air filter and flame coming out of your air filter housing. Unless you provide proof that your carb is igniting, I'm running on the assumption that you're just giving it too much fuel. How do you know that your intake manifold is smoking? Do you actually fire it up, wait for it to backfire and immediately take off the carb before the smoke dissipates? I find that /highly/ unlikely.

Lean means a low amount of oil. Rich means a high amount of oil.
 
Sorry about that,
From what you are describing i too don't think i am backfiring but i am still not to sure what the problem is. Also how would i limit the amount of fuel going into the engine. I have tried adjusting the throttle as well as idle and throttle cable but problem is still there.

Thanks
 
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Lean means the air to fuel ratio has too much air.
Rich means the air to fuel ratio has too much fuel.
Both conditions are tuneable by adjusting the slide needle clip position, fuel jet, idle mixture screw (If carb is equipped with one. Not to be confused with an idle speed adjusting screw.), and float height. Sometimes an intake leak causes a lean condition that cannot nor should not be remedied by carburetor tuning. An intake leak needs to be sealed before proper carburetor tuning can occur.
This is a common point of confusion that has been perpetuated for a looooong time.
Low oil ratio is just that, a low ratio or less oil to fuel.
A rich oil ratio is just that, a rich ratio or more oil to fuel.
The confusion comes into play when the words lean, rich and ratio get jumbled about because they both are used when describing fuel systems on 2-stroke engines.
 
Thanks for that. I will check for any air leaks in the intake and if there re any i'll seal them up. If not i will have a go at tunning the carburetor a bit to see what happens.
Thanks,
 
Faulty Cdi, or ground wire, the spark is going off at the wrong time, this will happen if you press the kill switch and let it go several times, Could be a bad kill switch too
 
I have checked the leads as well as the plug. Although i still have the same Chinese plug that comes with the bike, could this play a problem. The ground wire is straight on metal so it should not be that. Don't think it is the kill switch.
Thanks.
 
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