Why has a cg125 got me stumped

[Green1]

I'v been messing around with another cg125 the last couple of days but this one has me stumped.
Its had a full service carb cleaned and valves adjusted it starts dead easy when cold with a perfect spark but when warm it backfires coughs and farts before stalling.
when it does run it struggles under load when its cold it will do 30ishmph but as soon as its warm it gradually grinds to a halt.

Mick   

[Bitsa (Ralph Wright - RIP)]

Mick
Am I right in recalling the points and condensor is in the flywheel?If you are happy with the carb setup when she warms up this stuff starts to break down.Really cant remember so jog my memory and maybe I can help you out.I personally liked the CGs.
Cheers
Ralph

[Green1]

Sorry Ralph forgot to mention its a 1996 cdi bike
Didn't the early ones have the points in the head

Mick

[Bitsa (Ralph Wright - RIP)]

Mick
Thats way past the time I last worked on them.As i said though if you are 100 percent with the carburation the electronics tend to break down when hot.Never took to cdi units and cant remember where the friggin points are thought still in the flywheel Bryan will confirm that.
Cheers
Ralph

[Green1]

That's what I thought good job cg bits are cheap ordered a new coil and another cdi unit and fixed a couple of dodgy crimps so fingers crossed.

[Bitsa (Ralph Wright - RIP)]

Excellant wish the best
Cheers
Ralph

[Green1]

I was going to shove it in the truck tomorrow to avoid  paying £25 a day parking but never mind.

[Bryanj]

I had a c50 doing similar years ago, check the compression as the restricted engines can burn the valves just enough to cause problems

[LesterPiglet]

Does this CG have automatic choke?

[Green1]

There's no auto choke it just got a little lever on the side of the carb.
I haven't checked the compression yet but it just kicked back bloody hard so it can't be to bad. 
There was a small air leak around the head of new exhaust fitting it properly seemed to improve tick over slightly.   
 
Mick

[Green1]

Changed the plug cap and its still the same it has a brilliant blue spark.

[Bitsa (Ralph Wright - RIP)]

Mick
Still think electrical coil ok?
Cheers
Ralph

[Green1]

Not tested the coil I'm just going to swap it when the new one arrives

Mick 

[Green1]

The new coil arrived so I fitted that wish I didn't as it made it a lot worse there were only about 4 strands of copper in the new lead.
Just as I was about to give up the new CDI arrived plugged that in and it fired up instantly  took it for a run and its perfect no need to mess with the carb or anything.
The only thing it needs now is a speedo as it just goes around&around&around&around around&around&around&around

Mick

[UK Pete]

Nice one mick, i know what your saying about some of the coils out there
pete