CG125 Bike power losing

[georgewells]

Hello and thank you for your previous help with this CG bike.

The bike is now starting within a few kickstarts, to be very honest we have no idea why it now works properly it just started a few days ago and has been ok since.

We have a new problem that you may be able to assist us with.
It has developed a problem at the top end of the power range, when the throttle is opened up fully it acts like it has hit a limiter of some description.

The only way i can describe this is a fast pulse of firing and popping, it is like the bike wants to go but it cannot.
We really need to fix this very soon as my grandson says its frightening trying to get out into traffic from junctions and such.

Any advice is appreciated.
Kind Regards.
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https://www.chattinbubbles.co.uk/
A forum created by my grandsons friend.

[robocog]

What did you do? (between the time it wouldn't start to now where it does)

Did you remove/strip the carb and clean it?
Is it seated properly on the rubber inlet manifold and nipped up properly....ditto for the other end seated properly on the airbox
Checked all electrical connectors are clean and making good contact?
Twiddle the fuel mixture screw?
check the way the choke opens/closes and make a mental note
Have you looked at the plugs colour? / changed it for a new correct grade one?
Have you looked at the air filter? /cleaned oil or replaced it?
Put fresh fuel in there?
Checked/done valve clearances?

Just sooo many variables...


Regards
Rob
____________________
Needs a bigger garage...

[georgewells]

Did you remove/strip the carb and clean it? - This was done professionally.

Is it seated properly on the rubber inlet manifold and nipped up - Yes it is properly fitted.

ditto for the other end seated properly on the airbox - This may be of interest, it has never had an air box it is just a small cone shaped air filter.

Checked all electrical connectors are clean and making good contact? - Yes we have fine tooth combed the electrical system.

Twiddle the fuel mixture screw? - After much searching online to find this, yes we have tried it to the correct recommendations.

check the way the choke opens/closes and make a mental note - The choke is operating correctly, this bike now does not require choke to start/run.

Have you looked at the plugs colour? / changed it for a new correct grade one? - The plug was replaced as soon as we got it some weeks ago.

Have you looked at the air filter? /cleaned oil or replaced it? - As per above question.

Put fresh fuel in there? - Yes tank was emptied and cleaned out.

Checked/done valve clearances? - No, would not know how to do this.

Could this be air filter or air related?
Maybe not getting enough or getting too much?

On a further note my grandson took out the cylinder from the carborettor that moves up and down when you turn the throttle, he tried to dismantle it to clean the long needle and inside the cylinder, when he had done we realised there was more than one position the small C clip at the top of the needle could go on and we had not taken note of it so we put it on the middle one. If this makes any difference please let me know.

Thank You.
____________________
https://www.chattinbubbles.co.uk/
A forum created by my grandsons friend.

[Nexus Icon]

Have a look on eBay/breakers sites and get hold of the proper airbox and filter setup. It might be running a bit lean with a cone filter.

Modern engines can cope because they use a mass airflow meter to correctly fuel for any given air intake but an old carburated engine will just run lean without rejetting, etc.
____________________
Greetings from Shitsville!

[cb1rocket]

check for loose wiring connections to the spark plug, you have changed the spark plug so it may not be properly and its vibrating on and off at speed.

Also worth doing the valves, get the haynes manual if you haven't already. Re check the carb is actually on the air intake and manifold intake properly. Spray hair spray or wd-40 etc and if the revs rises at tickover you have an air leak. Also check you haven't kninked any vent tubes etc to the tank. Possible vent block casuing a vaccum in the tank.

[georgewells]

[cb1rocket]

[Nexus Icon]

[georgewells]

Could we take off the cone air filter and try it without a filter and see if it does the same? Would this point to the filter if it does?
Thank You.
____________________
https://www.chattinbubbles.co.uk/
A forum created by my grandsons friend.

[robocog]

My recomendations

Get an airbox and proper filter - fit them

They came with them from the factory- so by setting the carb to factory settings is not "safe"

get a haynes (or download one) and check the valve clearances!

Keep an eye on that plug - riding it with it "acting like theres a rev limiter" is it saying theres something really quite wrong with it
Riding it like this is asking for your next post to be
"whats the best way of filling in a holed piston"?

I very much doubt its running rich with a pod filter so look at the plug - seriously, look at it rather than a reciept that it was changed a while back....that will tell you whether its running piston meltingly lean

As for the clip- Id get that needly as hich as possible and work down by doing plug chops
Its cheaper and quicker to replace a soaked wetted plug at the roadside than have to rebuild the whole engine

Just had a look on the website in your sig
Theres a how to check valve clearances on a CG125 on there

Regards
Rob
____________________
Needs a bigger garage...

[Nexus Icon]

[cb1rocket]

[N cee thirty]

just get a airbox off ebay,there like £5
____________________
'00 Aprilia RS50 > '92 Honda CG > '99 Yamaha Fazer > '91 Yamaha RXS > '79 Suzuki X5 > 01' Honda Cg > 07' Honda Cg > 82' Kawasaki Z200 > suzuki gsxr 400 gk73a > honda vfr 400 NC30 Mod 2 Passed 09/06/2011

Jewlio Iglesias wrote: I actually did vote BNP once

[69chris]

as an experiment, before you spend money on airboxs etc...
try wrapping gaffa tape around the airfilter, aim to cover about half of it (thus restricting the airflow) and try the bike, if it improves then your running lean (expected with a cone filter, stock jetting and the needle on the middle clip)
give it a go an let us know

[georgewells]

It would appear we have an air filter box with a rubber joiner in the box of spare parts the man gave us with the CG.
I will have him fit this in the morning and return to tell you the result.
I will also get a new spark plug in the morning, what are the tell tale signs of a lean mixture on the spark plug?
Thank You.
____________________
https://www.chattinbubbles.co.uk/
A forum created by my grandsons friend.

[Nexus Icon]

[georgewells]

[N cee thirty]

te plug will have a white look about it

too much air being put through,the plug should never be wet if its combusting correctly
____________________
'00 Aprilia RS50 > '92 Honda CG > '99 Yamaha Fazer > '91 Yamaha RXS > '79 Suzuki X5 > 01' Honda Cg > 07' Honda Cg > 82' Kawasaki Z200 > suzuki gsxr 400 gk73a > honda vfr 400 NC30 Mod 2 Passed 09/06/2011

Jewlio Iglesias wrote: I actually did vote BNP once

[Nexus Icon]

An 'oily' black plug is a sign of running rich.

https://www.ooracing.com/images/SparkPlug-WetFouling.jpg
Or in less extreme cases..

https://www.ooracing.com/images/SparkPlug-DryFouling_000.jpg

And a normal plug should be a tan colour with very light deposits.

https://www.ooracing.com/images/SparkPlug-normal.jpg

Loads of good info here.. https://www.ooracing.com/tuningTips.htm
____________________
Greetings from Shitsville!

[69chris]

have a looky here (aimed at cars but same thing), and pics speak a zillion words......

https://www.classic-car-magazine.co.uk/articles/spark_plug_colour_guide_chart.html

[georgewells]

The plug appear as normal colour but i will change this anyway.
The air box and connector pipe is now fitted, the filter looks like new.
This has not made any difference to the problem we have with the top end of the power.

Are the valves as easy to set as they look on the guides?

Thank You.
____________________
https://www.chattinbubbles.co.uk/
A forum created by my grandsons friend.

[Nexus Icon]

Yeah, the valve clearances are easy on a CG. You just have to have a delicate touch when doing up the locknut, if I remember right. It has been 24 years since I had a CG.
____________________
Greetings from Shitsville!

[georgewells]

Ok the valves are set correctly, we still have the problem, would you adjust the C clip on the needle now to eliminate that as the offender?
Thank You.
____________________
https://www.chattinbubbles.co.uk/
A forum created by my grandsons friend.

[N cee thirty]

is the little accelerator pump on the side of the carb functioning/connected up to the throttle ?
____________________
'00 Aprilia RS50 > '92 Honda CG > '99 Yamaha Fazer > '91 Yamaha RXS > '79 Suzuki X5 > 01' Honda Cg > 07' Honda Cg > 82' Kawasaki Z200 > suzuki gsxr 400 gk73a > honda vfr 400 NC30 Mod 2 Passed 09/06/2011

Jewlio Iglesias wrote: I actually did vote BNP once