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CBR 125-RW6 - Starts but stalls/misfires, won't run


Guest CBromyard
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Hi all,


Wanted to pick your brains if I could on an issue I'm having with a newly bought 06 CBR 125.The bike starts usually with a bit of choke or throttle, but will eventually stall at steady revs or when at idle. The bike has a big bore dyne jetted carb and a custom exhaust.


Things I've tried:

Checking fuel pump/hose

Cleaned pilot jet and float bowl

Replaced ignition coil

Replaced choke cable

Cleaned air box

Changed engine oil

Changed spark plug

Checked for blockages/uncleanliness in tubing

Checked for any kinked hoses.

Tried different idle screw adjustments


First bike, just want to get it up and running, any advice most welcome!


Cheers

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Welcome to TMBF mate........ 8-)


When you say you checked the fuel pump, how? I'm not sure, but I seem to recall that I've seen on here that the fuel pump on the older CBR and CBF 125's were subject to a replacement recall....... :?

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Thanks mate :)


I'm definitely still a rookie, so bear with me if I get any names wrong. I'm sure it's not fuel flow that's an issue - the vacuum for the tank works as I've tested for it, and the carb definitely receives fuel as it can be drained.

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Tank breather seems fine, no hissing when petrol cap is taken off after it stalls. Suction to the vacuum hose pulls through the petrol, and carb float bowl will always drain off fuel when I try.


Cleaned out most of the carb, including taking off float bowl and chamber, main and pilot jets and reassembling. Now the bike won't start at all.


Booked in to see a mechanic but rather cut the two week wait and cost if I can get it running myself.... such an odd issue

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Welcome to TMBF mate........ 8-)


When you say you checked the fuel pump, how? I'm not sure, but I seem to recall that I've seen on here that the fuel pump on the older CBR and CBF 125's were subject to a replacement recall....... :?

 

is fuel pump exclusive to injected bikes? I remember having a mechanical fuel pump on 1 litre 1986 fiesta.

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So I've replaced the custom carb back to a working stock carb, but it still won't start.


Fuel seems to be going through to the carb ok. Air filter is clean. Spark plug has been changed, though with it not starting the plug is coming with a very small amount of wet oil on the end. Could this be a sign of flooding?


I've charged the battery and tried starting it with and without choke and throttle, no luck. Pulled out the plug and turned it over to see if that released anything in the engine, still no luck.

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Ok, so hands up, I made a stupid mistake. When I changed out the carb I connected the float bowl overflow tube to the tank. Nothing drained out of the overflow once this has been properly reset.


I'm pretty sure I'm dealing with a flooded engine. I've tried taking out the plugs and starting it to evaporate the gases, but no success yet. Plugs are coming out wet with oil after a few cranks.


Leaving spark plug out overnight and charging battery, see what j get. Engine doesn't sound close to starting, though fuel is being delivered to the carb, battery and ignition all sound good.

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Do you have a spark? Take the plug out and connect it back to the HT lead and rest the plug on the top of the head to earth it and try starting it. If you get no spark, you'll probably need a new coil but check your HT lead first with a continuity tester.


Your plug will be wet because of unburnt fuel.

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Thanks for the tip. It seems I've lost spark. I had another plug and ignition coil, replaced both but still no spark, which would explain why it won't start and the unburnt fuel.


One issue seems to lead to another! Not sure if there's much else I can do with what I've got, so I'll just have to wait until it gets to the Honda dealer next Friday


Cheers for your help everyone

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