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honda cg125

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martn26
L Plate Warrior



Joined: 13 Jun 2018
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PostPosted: 23:40 - 13 Jun 2018    Post subject: honda cg125 Reply with quote

hello guys.
i am the new one in bikes staff and i have problems with mine bike starting.
bike worked well, but suddenly stopped. irealized there is some electronical problems..there was no spark.
case is this bike is built by different parts. engine is somekind of honda cg125 chinese clone.

i managed to look closer the all electricy before i realized that mine cdi has stopped working. now i changed it, but spark aint very good. and it still wont want to start.

the thing is i am not very sure about i might have ruined mine ignition timing while i was checking staff. now i have a bad spark and bike wont start.

i have few questions.

1. is it possible to ruin timing or engine working even if i have new cdi box.
2. where could i get more instructions for setting ignition. for setting valve there are much more info.

what could be other issues, what i can check to solve?

thanks for help. [/i]
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WD Forte
World Chat Champion



Joined: 17 Jun 2010
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PostPosted: 15:34 - 14 Jun 2018    Post subject: Reply with quote

martn26

It sounds like you have a Honda CG125 with a chinese clone engine?
Who fitted that and why?
they are all easy to fix/mod/bodge but show us a pic of what you have and what you've done.

your English is a bit odd but at least you used the return key and didnt type a block of text, so points for that.
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Teflon-Mike
tl;dr



Joined: 01 Jun 2010
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PostPosted: 21:19 - 14 Jun 2018    Post subject: Re: honda cg125 Reply with quote

As above, and I assume english not your first language.

martn26 wrote:
1. is it possible to ruin timing or engine working even if i have new cdi box.

If its a CDi engine.... then the spark timing, is fixed by a lugg on the generator rotor passing a sensor bolted to case.

Usually there is no adjustment. The timing is right, or you get no sparks.

The sensor may have fallen off, or some~one might have tried to change timing by filing holes; Or the rotor has sheared its 'key' or not been fitted or the sensor lugg is damaged.

Otherwise, no, spark timing {as oposed to valve timing}, is factory set and non adjustable.

martn26 wrote:
2. where could i get more instructions for setting ignition. for setting valve there are much more info.


Above should have answered. Ignition timing is factory fixed, there are no instructions for altering it, as theres no service adjustment provided, as it shouldn't be necessary.

martn26 wrote:
what could be other issues, what i can check to solve?


start with a workshop manual. Follow instructions for basic service.

If the valve timing and the valve lift is in error because of badly adjusted tappets, then nothing else will work right either.

Old engines are old engines, and you need three things for life:
1/ sparks
2/ Charge for sparks to set on fire
3/ Compression in the cylinder for fire to 'push# piston, not past it.

You have checked sparks, you say and now have one. CDi unit might not be the right one for the bike, and giving the wrong spark timing, that could be worth checking, but most Small Honda engines and Chinese coppies and derivatives use essentially the same box of electrickery, so if you have spark, shouldn't make 'too' much odds provided it is for a small honda or chinese copy or derivative.

Charge.. fuel and air mixed by the carburettor... too many leap straight to the carb and start fiddling.... BUT if you have been trying to get engine with no sparks to start, good chance that the carb has been sending charge to the cylinder with nothing to burn it... and poor or no starting is likely to be from 'flooding' the spark plug trying to set fire to however many cycles worth of fuel that has dewed out of the air stream going into the engine, and made the mixture far to rich to burn.

Clean sparkplug; kick or spin engine over for a few minutes with the plug not in to try clear any 'dew' that has gathered in there; try again

DO NOT rush to look at the carburettor, you are more likely to make problems than solve them,

Compression; rule of thumb, is that if you stick your thunb over the spark plug hole whilst kicking or cranking, you should feel the pressure made by piston moving, and it should try and make your thumb come off the hole. If not, you probably dont have enough compression, and either the valves aren't closing properly, or they aren't sealing properly, or the pressure is getting past the pistion rings in a worn cylinder.

You can use more sophiostcicatred compression testers, but these are often little more accurate on a little engine, and wont tell you much more than your thumb, which is the first test, whilst cranking to clear.

Tip; the fact that bike used to work, does not tell you why now, it dont.

When fault finding you have to go by what you see..... and if you apply any 'history' the first place to look is at what you have done, since you started looking at faults.

You used to have sparks, and bike used to run... then you didn't
You found sparks missing.....
So looked at electrics..... ultimately conclusing that CDi unit was faulty.... and changed it..... and got sparks back.
What ELSE did you fiddle with along the way?
Check wires, check connections, check the things you have touched. These are the most likely places faults have been made.
BUT... as said, histpory is only of partial interest, and problem might NOT be in there....
go by what you can see, and bike needs sparks, charge and compression... and it could have been missing ingredients of had faults you DIDN'T spot before you swapped CDi.. so dont dismiss anything, work on the known, and what you can see here and now, and use that to backtrack through to find root~cause of problems.
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martn26
L Plate Warrior



Joined: 13 Jun 2018
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PostPosted: 22:10 - 16 Jun 2018    Post subject: Reply with quote

thank you guys for different ideas.

I start checking again next week, and then i can make some pictures.


and for sure, mine mother language aint english, i am estonian.
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WD Forte
World Chat Champion



Joined: 17 Jun 2010
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PostPosted: 15:31 - 17 Jun 2018    Post subject: Reply with quote

martn26 wrote:
thank you guys for different ideas.

I start checking again next week, and then i can make some pictures.


and for sure, mine mother language aint english, i am estonian.


Ahh I see, no problem

The good news is,
these bikes are quite easy to fix and get parts for cheaply
so you should be able to sort it out without too much bother
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