CG 125 S 2001 running and idle issues.

VONLONG · L Plate Warrior Joined: 06 Dec 2015 Karma :

Good morning all, im struggling to work out some problems i am having with my commuter.
Basically i was heading down an A road at 55mph and started to head downhill. I tyhink i pretty much redlined the bike and it cut out on me. As the bike speed dropped and i let go of the throttle, everything kicked back in, so on i went. Once home i gave it a quick look over and there seems so be what i can only describe as a bit of an airy fart noise coming from the top of the engine.
This was last friday. i didnt ride the bike again until the monday. the noise was still there but it was running fine.
On my way home on the tuesday everything started to cut out again. all power dropped at a set of lights. had to rev it a lot on biting point just to get over the junction. then i got a couple of backfires. then it ran ok for 10 minutes then the same again. after that it wouldnt start up. ended up getting a local recovery guy to pick me up. he had a bit of a gander and was confused too.

i starts now but wont idle and dies within 3 seconds. if i keep the revs up it ticks over but this isnt good.

any ideas where to start? could this be electrical or mechanical?
i have had a good look on the forum and there is lots of advice for CG's but im just very unsure where to start looking and also what im looking for.

any help would be greatly appreciated especially by any Honda veterans.

thanks is advance
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Luckyfish13 · Renault 5 Driver Joined: 30 Nov 2015 Karma :

Start with the basic tests for spark, timing, compression, and then fuel mix.
It sounds like maybe the o ring on the piston heads been damaged or knocked out of place...
It sounds like spark and timings are fine cos it runs, so if you have decent compression (> 100psi at least) then check the carbs especially the fuel/air mix screws. They can get knocked about and settings change pretty easily at high speed and engine vibration...Google will tell u the standard settings...
If not open up the carb clean out the jets and all and make sure there's no air leaks where the carb connects to inlet manifold...
Also check the throttle cable is opening the slide on the carb as it should

VONLONG · L Plate Warrior Joined: 06 Dec 2015 Karma :

cheers LuckyFich . how exactly would i check the pressure of the compression? as in how would i know how much it is putting out??
im gonna start on teh rest now Smile

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Luckyfish13 · Renault 5 Driver Joined: 30 Nov 2015 Karma :

Compression tester

www.ebay.co.uk/itm/8-Piece-Car-Motorcycle-Petrol-Engine-Compression-Test-Tester-Tool-Kit-Guage-/272022991419?hash=item3f55d5723b:g:jZYAAOSwo0JWJ65E

Keep us updated bro!

VONLONG · L Plate Warrior Joined: 06 Dec 2015 Karma :

cheers mate. ill pick one up asap and let you know how its going Smile

)
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Rob Fzs · World Chat Champion Joined: 07 Oct 2015 Karma :

You might aswell just put a new piston in and some new gaskets, they probably cost the same as that compression tester as it does sound like its seized and got going again, my cg did similar
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'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> Yamaha RD350 YPVS F2 > Kawasaki ZZR 600 D1 > Yamaha TZR 250 2MA >Suzuki TL1000R > Yamaha TDR250 > Honda 929 blade > Suzuki SV1000 > Honda H100
Mod 2 Passed 09/06/2011

VONLONG · L Plate Warrior Joined: 06 Dec 2015 Karma :

so your piston seized up?? i have also noticed a small amount of residue on the engine casing. could that be piston related??
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Rob Fzs · World Chat Champion Joined: 07 Oct 2015 Karma :

yes, must have over heated or something and was never the same, you can do a cg top end rebuild in an hour, it's really simple
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'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> Yamaha RD350 YPVS F2 > Kawasaki ZZR 600 D1 > Yamaha TZR 250 2MA >Suzuki TL1000R > Yamaha TDR250 > Honda 929 blade > Suzuki SV1000 > Honda H100
Mod 2 Passed 09/06/2011

VONLONG · L Plate Warrior Joined: 06 Dec 2015 Karma :

okay cheers mate. im gonna take some stuff apart today i think. do you have a supplier that you have ordered from that is reliable for the right size piston? just because i read on here that someone ordered one and it was wrong.

thanks
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Rob Fzs · World Chat Champion Joined: 07 Oct 2015 Karma :

Well you would have to measure the size of the bore to make sure it's not been rebored before else you can just fit a standard piston
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'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> Yamaha RD350 YPVS F2 > Kawasaki ZZR 600 D1 > Yamaha TZR 250 2MA >Suzuki TL1000R > Yamaha TDR250 > Honda 929 blade > Suzuki SV1000 > Honda H100
Mod 2 Passed 09/06/2011