I'm so confused

Todd Casey

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10:43 AM
Joined
Sep 24, 2016
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I've had my 80cc China motor for about three months now. Did the install, put a champion cj7y plug in and ran like a champ. Followed manufacturer instructions for fuel mix for first three tanks of gas and then for after. Was running perfect. Got to work on day and it ran great. Went to go home and it wouldn't Rev up under load and went like ten mph for the next couple weeks. Now I have to pedal just for the engine to get rpms. Replaced magneto cdi plugs carb throttle handle and cable. Checked all bolts with torque wrench. Changed all of the gaskets. Now what. I'm ready to toss it and by a new one
 
checking torque doesn't always work for head studs as they sometimes bind inside the acorn nut - clean it well and look for oil residue around head

if muffler came apart inside or got clogged somehow, you can loosen it a bit to test

lifting choke lever a bit while it's running can sometimes tell you something too
 
I don't have any noticeable leaks. Like oil or blackness anywhere on any gasket areas. I do know it doesn't like having baffle in muffler. The compression is really high. I mean it seams so. Im not a two stroke mechanic, but air fuel and spark are present. Like I said I'm absolutely stumped.
 
does it run better without the air filter? then you need a less restrictive one.
check the crank seals for leaks.
plane the head surface flat. they often are warped from the factory.
are you using ethanol-free gas?
have you tested the carb to see that the float valve is fully shutitng off when the float is up?
install a fuel filter in your gas line.
drop the needle to the lowest position (clip to the highest position)
 
Could be something simple like the float needle not seating and allowing to much raw fuel through the carb. That's where I would start by leaving the fuel valve open to see if gas leaks from the carb while not running. I would pop off the head and look for scoring on the cyl. walls while waiting to see if the gas leaks.
 
So took head off and exposed piston. It has alot of scratches on the sides. And it slides side to side quite a bit. Not sure if it's the wrist pin .
 
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Piston and cylinder are gouged super bad. Guess I need to rebuild
If your doing a new top end make sure to clean all the crap out of the case. Kings has engines on sale for 74 bucks. You can barely do a top end for that, and you won't have to worry about not getting all the crap out of the crank.
 
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