engine bogs out and dies when I give throttle

[stephen7689]

I have an 80cc China engine it ran fine for first couple of tanks of gas but now when I give it gas it tries to die and the engine jumps like it's not always firing only enough to keep bike running I took top end off and piston was covered in black soot and really wet so I cleaned that off and gonna try it again anyone got any idea what could be the problem

 

[Deleted member 12676]

that "jumping" is a problem in the ignition system.
read this troubleshooting guide: http://www.dragonfly75.com/motorbike/testCDI.html

 

[crassius]

if it is smoking a lot, you've forgotten to shut off petcock, so now motor is full of fuel - keep it running till it clears out

otherwise, it may be very rich due to float bad or main jet coming loose

 

[Nate888]

sounds like it's running too rich and maybe the electrical also has an intermittent short. go over all your connections and replace any wires that look too thin, have questionable connections, could be damaged, etc. make sure cdi is mounted well, so it's not gonna pull its wires and so the positive can't accidentally ground out against the frame, a stray wire, etc. optionally spray flex seal on cdi and all its wiring to protect against moisture, although it's nasty s**t and I highly recommend against using it anywhere else on the bike.

if you're running the manufacturer's recommend gasil ratio, that's not helping. instead use a full synthetic (snowmobile/hi performance marine/hi performance full synthetic chainsaw oil are all good) and go more like 33:1 (depending on altitude, tuning, etc. anywhere from 32-42:1 might be optimal. between 30-35:1 is safe side and works most everywhere)

finally try adjusting the needle jet leaner our replacing it. follow Jaguar s method for going smaller needle jet

 

[stephen7689]

OK I'm gonna give all that a try here thanks guys

 

[skyash]

If it runs then died when you accelerated how is that wiring? Dirt or block in the jet will let it run then you give it some gas and it sucks the dirt in hard and cuts out back off the gas and the dirt drops and it runs again

 

[stephen7689]

I bought new carb and it did the same thing so it's not the carb

 

[skyash]

It still sounds like air /fuel .if it's electric problem let us know always good to hear how to Fix something

 

[stephen7689]

I put a better high performance spark plug in it and now it runs better than ever starts right up just having a a problem with it holding an idle I've adjusted card needle and idle screw and the adjuster to the throttle and still won't hold an idle and also I keep breaking bolts I've even bought new higher strength ones and they still break off in engine anyways I can prevent that

 

[skyash]

Torque wrench might help. I've had plugs do that but only after you check everything you find out the problem .