CBR running issue after many new parts

[x alex x]

Hey all,

My GF's CBR has been a bit of a headache since I picked it up, I bought it cheap and in bits but once together it passed an MOT and seemed to run fine.

After a while it misfires and dies then won't start again. Plug always looks oily.. Once cleaned it won't always go again and will take a few hours or over night, some times it will struggle to start too and do the misfire thing.

It will leak fuel out of the overflow sometimes too.

So far I have replaced various parts (not all because of this issue)

Carb from a running bike
New coil & lead
Plug
Air filter element

Only on 7k miles and engine compression is at about 145psi, standard too, valve clearences to spec and the breather pipes aren't bloked

I'm kind of stuck now and really can't work it out.. Unless it's burning oil through the HG or something but there's no grey/blue smoke at all.

Any help would be great I was sure a new carb would sort it out.. Trying to get her into bikes and this one is putting her off, bought it because I wanted something more reliable than the 125 2 strokes I used to have

Thanks!
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Rides: Yamaha FZR 750 & KMX 200
Drives: 2007 Fiat grande Punto Sporting 1.9 Multijet, Remapped, 194BHP

[kramdra]

If the replacement carb is leaking that is probably the issue. Carbs should never leak from overflow - it means the float is not doing its job. I would also check oil if it stinks of petrol, replace it.

Its easily fixed, take floats off, clean them and the seats. New floats are about 40 quid but if the rubber tip has no visible damage they are probably just sticking - rub the aluminium part of the float valve with aluminium foil. This has worked on all 4 bikes that I've had overflow issues with, and the 24 year old 250 has the original floats.

[x alex x]

Thanks for the reply, the overflow only happened a couple of times after trying to start it, happened with the other carb too though but I suppose it's not impossible for this one to have an issue too.. I put it down to it being on a slant and on the side stand as that's the only time it happened

I've had it apart and measured then float height which was within spec and all looked well
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Rides: Yamaha FZR 750 & KMX 200
Drives: 2007 Fiat grande Punto Sporting 1.9 Multijet, Remapped, 194BHP

[B0ndy]

After it dies and you can't get it running again, do you get a spark?
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CBF 125 -> CB400SF -> GSX600F -> ZX6R (G1) -> GSXR1000 K4 -> ZX6R (B1H Stunt bike) -> VFR800 -> R1 5PW -> Sprint 1050 -> Fireblade 929 -> ZX10R C2H -> GSXR1000 K3

[misscrabstick]

I do wonder if it's flooding itself due to float/needle issues, definitely check the spark though next time you have a non start just for elimination, it's not unheard of to have multiple issues.

[x alex x]

Yeah it still sparks after it has cut out.

I've just had the carb off again checked it over carefully and put it back to standard.

Started and ran OK apart from the revs hanging a little but I let it warm up but cut out and won't start again, plug is a little sooty but otherwise OK. Cleaned it and still won't run but sparks OK.

Popped the fuel pipe off the carb to check its coming through OK (it is)

Forgot to say I replaced the rubber inlet boot too as it didn't look great.. That was another time I thought I'd found the problem lol

No flooding though now it's on level ground I think the overflow was down to it being un level for a while turning over
____________________
Rides: Yamaha FZR 750 & KMX 200
Drives: 2007 Fiat grande Punto Sporting 1.9 Multijet, Remapped, 194BHP

[x alex x]

Thanks for the replies though everyone

Forgot to say it cut out after I turned the air/fuel screw half a turn out, put it back to how it was and it won't run.. Plug is clean with a nice spark its getting fuel too as I can smell it on the plug.
____________________
Rides: Yamaha FZR 750 & KMX 200
Drives: 2007 Fiat grande Punto Sporting 1.9 Multijet, Remapped, 194BHP

[Vincent]

Which model CBR is it? (appologies if mentioned already).
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Space Is Deep

[x alex x]

[Vincent]

You say the plug looks oily...next time give it a sniff and see if it's fuel rather than oil. If so, deffo a fuelling problem, choke stuck on maybe.
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Space Is Deep

[x alex x]

Did that earlier, deffinitly fuel.

I'm starting to think I have a carb issue with with replacement too.. It all points towards that even though I was assured it was fine and it's very odd that it would have the exact same issue.

Dear me.. I choose a Honda 4 stroke over a 2 stroke for her because I just don't have the time these days
____________________
Rides: Yamaha FZR 750 & KMX 200
Drives: 2007 Fiat grande Punto Sporting 1.9 Multijet, Remapped, 194BHP

[kramdra]

Honda 4t 125's are some of the lowest quality bikes you can buy

It does sound like fuelling and float. Have you given carb a thorough clean, ensure all passages are clear and set to factory settings?

Carbs, generally, should not leak unless really leant over to the point of being dropped or crashed, so I would say you do have a float problem.

[Vincent]

Does the carb have a proper overflow? So the fuel doesn't run into the cylinder if the floats are sticking?
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Space Is Deep

[Suntan Sid]

What sort of carb is it, if it has a needle, what position is the clip at?
If the clip is not in the middle position, move it there try again and start from there!
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"Everybody needs money, that's why they call it money!"

[x alex x]

Not sure about them being the lowest quality bikes.. It's put together brilliantly.

The carb is all standard with needle position etc.

Anyway... Got a mate with the same bike and we ended up switching CDIs and she started and ran perfect! Ordered one off eBay for £13 so I'll see how it goes
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Rides: Yamaha FZR 750 & KMX 200
Drives: 2007 Fiat grande Punto Sporting 1.9 Multijet, Remapped, 194BHP