Loss of Top End Power

CENTURION

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My Zeda 80 has been running flawlessly since the winter, probably 150 or so 5 mile trips. Starts great,idles fine, 0-15 MPH it pulls real well. I'm running an NGK plug, 32:1 oil, new fuel filter, and the plug looks fine color wise. Over 20 MPH it four strokes on and off limiting the speed to about 23 MPH. Needle is on the middle notch, I notice if I move it up or down one notch it will barely run. I tested for leaks and it is tight, no throttle run-on, or lean symptoms. Fuel is only a few weeks old. I'm starting to suspect an ignition component? Any ideas?

Thanks.
 

CENTURION

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Disassembled and cleaned the carb, it's it happy self again at 34 MPH. A little piece of rubber or plastic was lodged in it.:D Thanks
 

DAMIEN1307

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Disassembled and cleaned the carb, it's it happy self again at 34 MPH. A little piece of rubber or plastic was lodged in it.:D Thanks
If your using Ethanol "enhanced" gasoline, be aware it is no longer 10% but is now 15% by executive order of "Brandon" here in the US now...Ethanol attacks rubber and plastic components of the carburetor. Two cycle motors are particularly susceptable to this.

You should check to see if part of your carby O ring is missing or part of the bowl gasket.
 

CENTURION

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Thanks, good idea, ran it for a 10 mile ride tonight plenty of power, no stumbling. 70's and 80's here lower humidity, great MB riding for sure. You can forget time on these things, and crank off 20 miles before you know it🚲
 

Emcee

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If your using Ethanol "enhanced" gasoline, be aware it is no longer 10% but is now 15% by executive order of "Brandon" here in the US now...Ethanol attacks rubber and plastic components of the carburetor. Two cycle motors are particularly susceptable to this.

You should check to see if part of your carby O ring is missing or part of the bowl gasket.
Funny you mention about this O ring. Both of my carbs do not have one..... Further more I'm only topping out at 23 MPH max just like him 🤔 is the O ring necessary? Sorry for posting on an old thread.
 

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DAMIEN1307

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Funny you mention about this O ring. Both of my carbs do not have one..... Further more I'm only topping out at 23 MPH max just like him 🤔 is the O ring necessary? Sorry for posting on an old thread.
It seals up possible intake leaks that are quite common with these...Just take your carby to your local autoparts store like O'Reillys etc. and have them match up the O ring size to the inside of the carby...You want the O ring to be a Viton or similar gasoline/oil resistant type of "rubber", especially more so if you are not using ethanol free gas, or is unavailable in your area, this will help prevent softening/swelling failure of the O ring.

Ps...The JRL BoFeng carbys usually come with these O rings already.
 

Emcee

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It seals up possible intake leaks that are quite common with these...Just take your carby to your local autoparts store like O'Reillys etc. and have them match up the O ring size to the inside of the carby...You want the O ring to be a Viton or similar gasoline resistant type of "rubber", especially more so if you are not using ethanol free gas, or is unavailable in your area, this will help prevent swelling and failure of the O ring.

Ps...The JRL BoFeng carbys usually come with these O rings already.
Thanks for the info, I did switch to Ethanol free 90 upon your recommendation so thank you for potentially saving me from a hassle down the line, means a lot.

I try to understand why do things work the way that they do. Now how does the O ring seal anything up considering it isn't around the opening that goes into the intake manifold. Just curious considering the air filter is right there.
 

DAMIEN1307

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I try to understand why do things work the way that they do. Now how does the O ring seal anything up considering it isn't around the opening that goes into the intake manifold. Just curious considering the air filter is right there.
The intake tube slides into the carby and makes contact with the O ring inside, thus sealing the intake from possible air leaks...just press the carby and intake firmly together while tightening it together to assure good, firm contact.
 
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