Bike too slow

Mp2003

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Joined
Jul 11, 2016
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7
About a week ago I bought a 2-stroke 80/66cc bike kit. I installed it and after startup problems at first I managed to get it running smoothly, the only problem is, it is way too slow. It struggles to stay at 20mph with the throttle wide open. I checked the carb and the throttle runs fine, so it's not that. I'm using 20:1 oil to fuel on a 26" mountain bike. PLEASE HELP!
 


FurryOnTheInside

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Sep 23, 2013
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3,685
Carb adjustment obviously, but
The entire electric system needs to be checked, fixed and improved from the keyway on the crank shaft all the way up to the plug gap. Lots of reading to do. Whole section on it. Most of the problems that come up are free or inexpensive to fix and not expensive to improve.
The engine needs fuel, lubricant, air, carburetion, compression, spark, exhaust, cooling.
 

Frankfort MB's

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Apr 3, 2016
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Your probably running too rich of a fuel air ratio..... If you pull your plug and its black on the end then your rich.
A quick fix would be too take air filter off, but to be right you need to rejet the carb to a smaller jet.
 

OTP

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Jun 7, 2016
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Give it time to break in. After about 200 miles mine runs so much better. It was pretty sad at first but now its pulling me up some steep hills with no problems. I was worried at first but happy with it now.
 

Mp2003

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Jul 11, 2016
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Give it time to break in. After about 200 miles mine runs so much better. It was pretty sad at first but now its pulling me up some steep hills with no problems. I was worried at first but happy with it now.
I really hope that's all it is.
 

Mp2003

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Jul 11, 2016
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Your probably running too rich of a fuel air ratio..... If you pull your plug and its black on the end then your rich.
A quick fix would be too take air filter off, but to be right you need to rejet the carb to a smaller jet.
I'm not home now but I'll check it in about an hour when I can. Thank you for the help.
 

Mp2003

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Joined
Jul 11, 2016
Messages
7
Your probably running too rich of a fuel air ratio..... If you pull your plug and its black on the end then your rich.
A quick fix would be too take air filter off, but to be right you need to rejet the carb to a smaller jet.
It was black and oily and I moved the jet needle to the leanest position, still nothing changed. Also how would I go about removing the air filter and would it still run okay without it.
 

Frankfort MB's

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It was black and oily and I moved the jet needle to the leanest position, still nothing changed. Also how would I go about removing the air filter and would it still run okay without it.
It will run ok just don't ride it too much like that because it will let dust and rocks and water in the engine.

What it does is it lets the engine breath more (think of it like your trying to breathe with a sock in your mouth then breathing w/o it.... Big difference in air flow) when it lets more air in it will lean out the mixture.

When you lower the needle all that does is the low to mid fuel:air mixture, the jet is full throttle adjustment
 

Mp2003

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Jul 11, 2016
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7
Your probably running a little too much oil btw.... 32:1 with full synthetic is perfect
I already put in 16:1 oil to fuel a few hours ago. It'll be a while until it's empty but when I do fuel up again I will do it 32:1 next time. Thanks for the help.
 
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