CG125 Running Issues

[jamhowe]

Hi all,

I'm new to the forum and reasonably competent when it comes to working on cars but don't have much experience with bikes and carburettors.

I recently got a CG in bits that was a friend's project - he had intended to powdercoat it and reassemble everything but lost interest.
I have assembled the majority of the bike other than the lights and have it running, I'm not 100% on my wiring effort but most things seem to be in place and it starts.

On first filling the tank petrol ran directly out of the drain pipe at the bottom of the float bowl, this was solved by shutting off the fuel, draining it, and tightening everything back up.
After a while I got the bike running, it will start up and ride but bogs quite heavily and won't allow for a full range of revs, when the choke is on the revs skyrocket, and as it gets warmer/is used more it seems to weaken and won't set off under load.

Could this be an issue with my halfwhit wiring, or is it wholly carb related? I have soaked the carb and intake with wd40 and noticed no variation in revs.

Any help is massively appreciated !!

[MCN]

They have three positions for the choke.

The lever is either:

Off for normal running.

1/2 Choke for nitwits as it does Hee-Haw and complicate the issue.

Full Choke for every cold start (even in a 30° Centipede British Summer)

Almost any engine likes a little enrichment for positive start-up.

The start sequence:

Petrol cock to Run position. (or normal)
Choke to Full On.
'Crack' the throttle open (about 1/4 turn or less is fine).
Hit the button/Turn the hoowur over using the kick-start. It's a genteel roll of the kick-start. You only need to kick it when it wont start and you are already late for an appointment.
The bastirt should start if fuel and spark is OK.

If no starty:

Choke Off.
Open the throttle to the stop.
Turn the beast over on the starter to cough out all the un-burned fuel in the cylinder and manifold. (This is called 'flooded' There is no sloshing of petrol involved, it is just too much fuel and not enough air to burn it.)

Go through the same cold start procedure.

If it fails to start then start looking at 'things'.
If you can smell petrol from the exhaust then there is surely petrol getting into the cylinder.
Look at the ignition.
Pull the spark plug and check for a big fat blue spark when the plug is held against the block and the engine turned over. If you have a pace-maker fitted get some other daft cnut to hold the sparky bit.

They are a bit lumpy when first started and need a bit of choke for a few mins.
It is fine to start the beast and ride off with choke fully on.
About 200 yards down the road you can fumble about between your legs for the choke lever and turn it to the off position.
Just don't do this at the bottom of a hill you wish to traverse.

The carburettor is a joy to phaph with. Not a lot in them so you can easily rip it apart and clash it together again after drowning it in carb-cleaner.
Take pictures of every step so you can put it together again.
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

[Easy-X]

WD40 probably won't cut it, get a can of proper carb cleaner
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Royal Enfield Continental GT 535, Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[WD Forte]

Spraying WD40 on intakes isnt to fecking clean it ya numpty !
It's a well known test for intake leaks
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bikers smell of wee

[Easy-X]

Ofc you can use WD40 for leak testing but that's not how I read it

<edit> grammar
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Royal Enfield Continental GT 535, Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[MCN]

[Easy-X]

The theory is it's of Scottish original and a combination of "numbskull" and "Humpty Dumpty"
____________________
Royal Enfield Continental GT 535, Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[jamhowe]

Hi again, it has spark and no problems with starting, it's just the running that's a problem.
I replaced the o rings on the intake and soaked it with wd again to check for leaks and it doesn't seem to have any.

When I start the bike up with any amount of choke now the revs are far, far too high to the point it feels I might be damaging the engine, and when choke is off it eventually settles but needs throttle to keep running and wont rev up at all without bogging, and I have the same problem with not moving under load after a couple of minutes.

It also backfires occasionally.

Any idea if it could be wiring related considering I slapped it together from a few boxes of bits and hadn't done it before? Or does it sound wholly carb related?

[BusterGonads]

The running issues described suggest the carb is badly set up. It could easily have been tampered with. A lot of them are (ruined in my opinion) in attempts to make something described as a 'cafe racer'. This usually involves ripping out the airbox and filter and sticking a pod filter on and wrecking the bike's performance and economy thereafter.

[jamhowe]

[Easy-X]

Blocked pilot jet maybe?
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Royal Enfield Continental GT 535, Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[Tankie]

Does sound like a blocked jet, clean the carb out carefully!
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Always learning, everyday is a school day

[BusterGonads]

[BusterGonads]