Engine idles but bogs and has no power when throtle is opened

[DuctTapedGoat]

But also there's 4 vent tubes, that's what confuses me and leads me to think it's a CNS.


I know it's a very ballpark statement, but I think it's an air problem. Either there's a vacuum leak in one of the gaskets (which can happen stock day 1), or your carb isnt' letting in enough air, as though the choke is acting up.

 

[Flyinggrape]

I thought vacuum leak myself. I made a new gasket to go between the cylinder and the intake tube. I also used liquid teflon sealer where to carb clamps onto the intake tube to prevent any leaks. The choke is a simple blade that swivles in front of the carb inlet so It isnt'the problem. I have run it with and without the air filter. It acts the same. I am not a newbe to engines. I have been into drag racing for nearly 30 years. I do all my own work from building engines to tuning carbs and ignition. I am sad to say that this simple piece of ($%(^%( has me stumped.

 

[rohmell]

the carb has the black aircleaner cover that sort of looks like a skull. Round with two screws holding it inplace and 4 vent tubes out the bottom.

Looks like Zoidberg

 

[DuctTapedGoat]

I know what you're saying about vent tubes, sorry. I thought you meant like a carb overflow tube etc. You have an NT carb.

LOL rohmell, it does.


I know you know your way around an engine, that helps - even if you're stumped!

I almost wanna say replace the cylinder's top and bottom gaskets, replace the seals, get a new set of rings and try it then.

How much compression does it have?

 

[GearNut]

Try taking the muffler off only long enough to see if it will run.
A plugged up muffler will cause your symptoms.

 

[Greg58]

Have you tried dissconnecting the kill switch wires, they sometimes arch across the gap between the contacts.

 

[Flyinggrape]

The engine has 140 to 150 psi cylinder pressure. I have taken the muffler off and disconnected the shut off switch. Nothing changed. I checked the float and it is not leaking and floats perfectly. cleaned all the fuel filters and the jet. Still no difference. It only runs because of the momentum from pedling it. Then it dies when you disengage the clutch. I think I should run it over with my truck next.

 

[GearNut]

Well, I understand that you are good with 4 stroke engines.
The basics of diagnosing a 2 stroke are pretty much identical.
The biggest difference is there is no cam timing to check out.

Have you tried a leak test specific to 2 stroke engines?
Here's a utube vid that shows how.
Note, you don't need a fancy air pump to do it. You can use a hand bicycle pump.
With these Chinese engines I wouldn't pressurize it past 5lbs. In the video he mentions 9lbs which is why I made that suggestion.
‪Leak Down Test For 2-Stroke Engines.avi‬‏ - YouTube