Whats wrong with my 49cc 2 stroke engine? PLEASE HELP!

[rob0101]

I have an engine that looks exactly the same as this.

The problem is that it idles fine with the choke on/closed, but when I open the choke it revs like crazy. And if I rev the engine with the accelerator it dies.

So far ive taken the engine to bits and given it a really good clean with wd-40, carb cleaner and compressed air but this has had no effect.

If someone could tell me whats wrong or what I need to adjust/fix/replace that would be great!

P.S. im having real trouble finding any information about this engine online so if anyone has some I would be very interested.

Thanks!

 

[GearNut]

I would start by making sure that the throttle in the carburetor is closing all the way down to idle speed. It sounds like it is stuck partially open, or the idle speed screw is turned in too far.
Also check the throttle cable for any kinks or bends which would prevent the cable inside it from moving freely, preventing the throttle cam from moving to closed position.

 

[rob0101]

Is the throttle in the carburettor the cylinder with a hole in it that turns when you pull the accelerator? If so when im not revving it closes so I cant see through the carb. So not sure its to do with that, will check again now though just to make sure

Thanks.

 

[adb140275]

its WAY too lean, you need to take the carb apart and clean it.

 

[robimagu]

Ensure that you've correctly installed the needle in the slide. The needle with the "c" clip should be UNDER the silver disk with the slit in it. I've seen pictures posted on this forum with it installed incorrectly. If it is install wrong, the needle will be pulled up with throttle application, but it won't reset properly causing high revs.

 

[rob0101]

Ok...

adb140275 - the carb is spotless, lol just to be sure i have cleaned and double cleaned it so im pretty sure its not that.

robimagu - "c" clip? silver disk with the slit in it? im lost! below is a diagram of my exact carb and a photo of my actual carb. if you could explain more?

as a thought, how easy do the fuel filters on the end of the hose in the fuel tank get blocked? adb140275 says its running lean, could it be clogged?

thanks!

 

[Bonefish]

Your throttle arm stop screw is too far in. It is causing your carb to be open, I can see from the picts and it is not fully closing. You need to back off the throttle arm stop screw. Pictured in your actual carb pict in the top right hand corner. back it off so that the circle/opening is not showing when your throttle arm is relaxed.

Hope this helps.

 

[Bonefish]

opps top left hand corner

 

[rob0101]

thanks Bonefish, i thought as i could not see straight through that it would be alright but i will adjust that screw in the morning and hopefully the results will be good!

 

[motorpsycho]

Your throttle arm stop screw is too far in. It is causing your carb to be open, I can see from the picts and it is not fully closing. You need to back off the throttle arm stop screw. Pictured in your actual carb pict in the top right hand corner. back it off so that the circle/opening is not showing when your throttle arm is relaxed.

Hope this helps.

yep, in the pic it looks like the throttle blade is wide open because the scew is in too far.
when you close the choke, you are starving the engine of air, and that's why it will idle down.
open the choke and a rush of air is getting sucked in causing the rpm's to skyrocket.