CBR125 has stumped me...

[miss.metallica]

Hi all,

Really need your help fixing my cibber. It started playing up, hard starting, rough idle, revs doing whatever it likes, rising, falling, hanging etc. It progressively got worse to a point where now it wont start without the choke, and still hard to start then, and it comes to a stall and cuts out on the sidestand.

Before the obvious, heres what ive done:

-Stripped/cleaned carb (twice!)
-Checked float height, its bang on
-Replaced fuel and air hoses
-Checked all intake for and gaps/leaks
-Replaced fuel filter & valve
-Replaced throttle cable
-Tweeked mixture & idle
-Checked choke cable
-Drained & replaced fuel
-Redex

Im absolutely stumped, and annoyed, HELP!!

[gavcarter]

check ignition coil, battery, and triple check mixture screw.....

[miss.metallica]

Ignition coil was changed in January as it was causibg the bike to cut out everytime I slowed to a stop, and that was fixed and all was fine until this started

[gavcarter]

did you check battery voltage and spark plug / cap etc

I'd give it a good go over for air leaks too..

[MarJay]

When you stripped and cleaned the carb did you clean out the idle jet? Properly? With compressed air and carb cleaner?

This sounds like a similar issue to those I've had with both my old FZR400 and my pitbike. Both times it was minute amounts of crap in the idle jets in the carb(s).
____________________
British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[jjdugen]

Valve clearance?
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The CBR900RR has been sold. Aprilia Falco worms its way into my heart.
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[Rogerborg]

[miss.metallica]

Used compressed air and carb cleaner when it was stripped. Think its going to have to be cleaned out again. I cant come uo with any other reason for it other than blocked jets.
Thanks all

[Bunny Lingus]

Ok. I reckon you are fighting on two fronts - sparks or fuel. Are the symptoms the same as when the coil failed & was replaced, or different? I say this because I rarely have trouble with carburetors & you've replaced the coil once already. Do you think it could be the same problem as before or are you certain its fuel? You are very unlucky to have both those issues hit you in only four months. I would go back to what caused the first coil to break down. You need to eliminate one or the other..


Hold on, Hull City are all over Arsenal..
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Bunny Lingus & The Flipside Faggots

[miss.metallica]

Definitley fuel. The symptoms are different and since the cibbers are known for ignition coils going tits up, ive had to have it replaced every year since owning the bike, so by now im pretty familiar with the symptoms it shows. Besides that I cant imagine a brand new genuine coil failing within 4 months.
I stripped and cleaned the carb out once again last night, really spent time on it to make sure it was all clean. Will put it back on and see if all is well now

[Robby]

When you clean the carb, do you remove the mixture screw, squirt plenty of carb cleaner down its hold, then replace the screw and set it to factory settings (probably about 2 turns out).

The alternative thing I would look for is an air leak - maybe the carb rubber is split, or not sealing onto the carb or cylinder head.

If the revs are hanging then it points at either an air leak, or a clogged mixture circuit where someone has tried to compensate by tweaking the idle adjuster.

[miss.metallica]

Yep I removed and cleaned everything, even the choke and air cut off plates.
So I put the carb back on and warmed it up to reset the mixture etc, seems to be better, the revs arent majorly hanging anymore, only slightly when it drops down to 2k but I put that down to excess air from my k&n filter and aftermarket exhaust. Its starting without the choke so ill see how it goes.
My restriction comes off middle of august so a new bike is in the pipeline anyway, but I want it running ok to be able to sell or part ex on

[Robby]

What have you set the mixture screw to?

Usually when I come across a bike with the revs hanging, I open up the mixture screw a turn to give a richer mix at idle and close up the idle adjuster a bit to bring the idle revs down to the right point. The revs dropping slowly is usually down to a lean mix at idle, either due to carb setup or an air leak.

[miss.metallica]

1 3/4 out is the initial setting, then set the idle, then turn it back in 3/4. But like I say because of my filter & exhaust ive made it slightly richer to compensate for more air flow.
Ill have another play around with it

[miss.metallica]

Past few days ive tweeked the mixture, still pretty hard to start, but when I get it going and warmed up, now the mixture is bang on it idles perfect, no hanging revs. However, if I turn it off, and back on, even still hot, it still struggles to start. I looked around some forums about the stalling on sidestand, most were saying it was the float, but cant be in my case, but found someone who had exactly the same symptoms as mine, weirdly a new battery solved it. I got one today, it seems a little better but not cured. Im pissed having thrown money at it once again ugh. Going to try a new plug tomorrow, if not that im done, its new bike time...

[mudcow007]

i found soaking my jets in acetone (nail varnish remover) for 30 seconds made a world of difference to my supposedly clean carbs

a bottle cleaner will be £1 worth a go

[miss.metallica]

Interesting, ill get a bottle and try that then, got nothing to lose since new plug didnt make a difference at all

[miss.metallica]

Got some nail polish remover and also got a new insulator for the carb to engine, I noticed that it was worn and wasnt able to sit right once the weight of the carb & airbox is on, thought it was causing an air leak. But still nothing has worked. Frustated isnt the word...

[MarJay]

Have you checked the valve clearances? Have you done a compression check?
____________________
British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[miss.metallica]

Valve clearances done a few months back, hardly done any miles since then and compression is less likely as it does run perfect when its out, and wouldnt explain it stalling out on the sidestand

[Tbag]

A freind had similar problems with his, the Spark plug cap had got damp and was shorting over to the engine.. Get it running and look for a spark jumping across to the engine.

[bladerunner]

another back to basics.....is the tank breather blocked...take the cap off....is the fuel supply flowing as it should...blocked tank filter or kinked line to the carb?Youve done an aweful lot to the bike in the last few miles...what might be thought to be sorted might have added to the problem?!? if the HT lead can jump a 10+mm spark then I'd say ignition or at least HT side sounds good....the fact you say it needs choke to start even when warm sounds like fuel.....if its playing up again...drop a bit of fuel down the plug hole. if it runs right straight away for a couple of seconds...then you know its fuel related.if not I'd be looking at spark/compression check
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Current bikes...cbr929, KDX200's, Rd125lc mk2, RGV250's

[miss.metallica]

Checked the spark against the engine, its all fine there. I know fuel is getting into the carb ok as I drained it from the bottom of the float a few times after id had the carb through the ultrasonic cleaner, just incase there was the tiniest bit of water id missed after.
Fuel filter and valve are fine, ive replaced them new and also cleaned them once again.
I managed to get it going and warmed up yesterday, no/little hanging revs and idled fine on the stand. It ran perfect, better than it has in a long time. Then get back home, turned it off fot a while. Came to start again, same trouble. Argh!