Can anybody help with my daughters first bike. Honda CG125 2006 .

Picked it up cheap and now I know why . It has a miss fire under load but would tick over ok but miss also when you rev it .

So I have :-
Changed air filter ( noticed water in the air box ),
Taken off the carb cleaned main and pilot jet and checked they are standard sizes which they are,
Done valve clearances,
New plug has good spark,

Then by chance I noticed the exhaust and air inlet pipes on the AIR SUCTION VALVE where on the wrong way around ! This explains poor power as exhaust was being rooted straight into the air box replacing air and the presence of water in the air box !

Pipes 8 and 3 swapped.
AIR SUCTION VALVE - CG 125 CG125ES4 2004 UNITED KINGDOM - CG125ES4 - Sale Honda motorcycle spare parts microfiche origin

I've taken the valve apart and cleaned it and checked its operation as all is good.

But now , with it on the bike the correct way, the bike revs to 2000rpm at idle. The carb slide is right down and the idle mixture screw has no effect where ever i set it . Took it out an checked with a carb cleaner spray the all passages are clean.

I did notice that inside the throat of the carb to engine side that there was fuel lying there. And the float valve was not 100%

Is it possible that the float valve needle is flooding the carb , making it rev ?
Should I never see a pool of fuel inside the carb or are there times where I might . Pic shows valve after cleaning.

Any help would be appreciated cos then I can get back to my CBR1000fh
Thanks

 

As far as I know fuel should only be in the float bowl if the engine is not running. What color is the plug?

 

Hi, the plug color is a sooty black . Rich mixture then. Got a hawk exhaust gas analyzer which also shows its running rich , but the air jet screw has no effect . should screw in until it just stalls and then the other way until just stalls again then set it in the middle.

Had the carb off again and rechecked float height ( ok ) and blowed down fuel inlet while operating the floats to check the float valve. Seemed to close ok under quite a lot of blowing pressure.

Refitted carb, Started up again and still ticked over at 1500 to 2000 rpm . Let her warm up over 10mins . Turned off . waited a min then restarted. This time with little slide stop adjustment tick over rested at 1200 ish , normal as far as im concerned. So may be things just need time to settle down ?

Now she revs great with power and meaning with just hint of popping in the exhaust on throttle off .

Ride tomorrow . OH and I have another carb on the way and I also checked the CDI pickup coil bracket hasn't been slotted and so ignition timing messed with but all was good .

One more thing , I found carb pipe on a stud going nowhere and found out it should be going to the float bowl breather exit , so on carb refit i placed it there where it should be . May be the length that breather pipe has an effect on the pressures inside the float bowl ?

Cheers

 

I doubt that the length of the hose could change the pressure enough, but odder things have happened.
The needle seat may be worn, shaped more like an egg allowing more fuel to pass through when the needle is fully seated? This happened to my old FZR and caused a high idle/rich mixture.

Either way sounds like you've got the problem isolated and just flat out replacing the carb will probably solve the problem unless there is something wrong with the new carb.

 

So new (cleaner) 2nd hand carb is here. Cleaned and checked it over . Correct jets of main 90 and 38 pilot . Fitted it to the cg . Started fine , ticked over at 1100 ish when the choke came off. On a run it struggled with power a bit but that could be my perception as i'm used to the CBR. Plug colour is now light gray to brown which i believe is good. Still running at high tick over when I got home with engine truly warmed up . Off to adjust slide height now and to see if i can change the idle mixture via the screw where on the previous carb , i had no change in revs no matter what position it was in . Oh I also changed the carb slide and needles also.

 

Sounds like the air suction valve is not working.
Can you plug all the hoses to remove it from operation?
I would bet that the valve is letting air flow and causing high rev's.

Either that or its hooked up wrong. Still, I'd plug the lines to remove it from operation. Its basically an EGR.

 

Yea , cheers. It was connected wrong to start with . Had exhaust going into the air filter box !!

New carb has cured the problem . Went for another run then when the engine was off choke and hot , brought the slide height down to get a good tick over :icon_smile .

I've got a compression tester to test um .. compression test the engine ,which will convince me all is well , as it lacks a bit of power . I think its probably my perception though, as I'm used to the cbr No engine miss fire now .

Good point though, I may may block it up and try another run.

thanks all , for your help.

Now, is there a ' how to change fork seals on a CBR1000fh ' ?