HONDA CBR125 06: Bike only runs on choke

laurence231 · Derestricted Danger Joined: 19 Dec 2018 Karma :

Hello!

(apologies if post is duplicate - posted last night but it hasn't appeared here!)

I recently bought a 2006 CBR125 a couple of weeks ago as my first bike, working but quite cheap so was expecting issues to work on as time went on. The choke cable turned out to be siezed in the carb, so I recently replaced all the slider/spring and cable (I had to buy a spare carb as it was cheaper than just buying the slider/spring from a dealer who wanted £90 for a brass slider and spring!)

My latest problem, now I have fixed this is that the bike runs great when starting (air filter replaced too btw) with the choke on, but the moment that I put the choke off, the bike cuts out (even after a long ish ride with the choke part open).

From some research online, apparently its most likely cause is that a pilot jet in the carb is blocked/clogged, and carb should be disassembled and cleaned. At the same time, as a beginner to mechanical work, carb dissasembly seems a lot of work at best, and risky too. Should I try spraying some sort of carb cleaner down fuel pipe to try and clean the inside of the carb? Something like seafoam which I see mentioned a lot? Or should I not delay the inevitable and just disassemble and clean the carb? (I have a spare carb to practise on thanks to buying another carb to fix the choke assembly).

Apparently another alternative might be some sort of air leak although I imagine this is less likely. Anyone have any advice for me at this stage as to how I should proceed?[/b]

Meatybeaty · World Chat Champion Joined: 10 Apr 2016 Karma :

Did you take the carb off your bike and replace or did you replace the parts with parts from the replacement carb, and when it idles what is the
rpm?

laurence231 · Derestricted Danger Joined: 19 Dec 2018 Karma :

Meatybeaty · World Chat Champion Joined: 10 Apr 2016 Karma :

Yes the 1500rpm should be just about right at idle, but if that's with choke on as well then you should be looking at the carb, does the idle adjuster help at all ,or does it just stall with increasing

bikenut · World Chat Champion Joined: 21 Nov 2011 Karma :

See cmsnl for the exploded views which can only help. A quick read of your post suggests carb needs cleaning, which means starting at the fuel filler cap.
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laurence231 · Derestricted Danger Joined: 19 Dec 2018 Karma :

Meatybeaty · World Chat Champion Joined: 10 Apr 2016 Karma :

The idle screw will only adjust the accelerator stop, could be that its wound out too far , this is the adjuster number 5 in the picture, found on the righthand side of the carb

laurence231 · Derestricted Danger Joined: 19 Dec 2018 Karma :

Nobby the Bastard · Harley Gaydar Joined: 16 Aug 2013 Karma :

What condition are the carb rubbers in?
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trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Sprint ST 1050

laurence231 · Derestricted Danger Joined: 19 Dec 2018 Karma :

Meatybeaty · World Chat Champion Joined: 10 Apr 2016 Karma :

Tankie · Crazy Courier Joined: 24 Feb 2017 Karma :

Blocked idle jet , strip and clean the carb properly.
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Always learning, everyday is a school day

Nobby the Bastard · Harley Gaydar Joined: 16 Aug 2013 Karma :

Grubscrew · Scooby Slapper Joined: 23 Dec 2018 Karma :

I had a ZZR1100 with same issues some years ago. B@st@rd bike.
Any way, have you looked at the air filter, just a thought, can have the same symptoms.
What about fuel delivery? Not aware of the workings of your particular bike, is there a fuel pump giving agro or dodgy fuel filter.
A partially blocked pilot jet can cause same issues.
Good luck.
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FJR1300/CBR1000F

laurence231 · Derestricted Danger Joined: 19 Dec 2018 Karma :

Thanks all for the ideas and suggestions!

Re. Air filter, I put in a completely fresh one the other day. Got a new spark plug coming in the post too as thats probably never been changed.

What I did today was run Wynns carb cleaner through the fuel line and into the air intake of the carb with the engine running today, and I think I may have had some minor improvements (albeit maybe coincidental). I have also added some fuel additive to the fuel. The bike is rideable, so will see how it performs over a couple of days as the fuel additive (apparently) cleans the fuel system and change the spark plug too.

Basically, to sum up my ride I just went on and observations -

1 - With choke open, normal ignition no longer seems to do the trick. I have to hit the ignition and pull throttle for a second. Then, it idles at 2000 rising to 2500 ish.

2 - I then put the choke 90% down (the tiniest bit still open) and it idles between 900 (where it cuts out) and 1500. I observed a lot of fluctuation of idle rpm as I was riding.

3 - Choke fully 100% on will make it idle at about 800 and then it dies rapidly. Even with the idle screw adjusted further, this always seems to happen.

I will try the spark plug and see how the additive does, and see if any improvements. If not then I guess it'll be time to take the carb out and have a play around with it! Any further thoughts/ideas appreciated

jaffa90 · World Chat Champion Joined: 06 Apr 2016 Karma :

As Tankie suggests. Wink

laurence231 · Derestricted Danger Joined: 19 Dec 2018 Karma :

Thank you to you all for your help!

I appear to have resolved the issue (at least for now). I replaced the spark plug with a fresh one and the new one seems to work better. I am sure the idle jet still has issues, as there is some fluctuation in idle rpm, however the bike starts and idles well and hasn't cut out yet, with the choke off Very Happy

Now the bike shouldn't be running so rich permanently, hopefully its a lot longer before this spark plug gets ruined! Will update here if any more issues arise.