Honda CBR 125 - a few minor problems

[adamcfc]

Just purchased a Honda CBR 125, it has a few little problems, just wondering if anyone can give some advice.

1) On de-acceleration, and after the bike has been revved and the revs are dropping, flames pop out the exhaust every now and again. This is a sign the mixture is too rich? To fix this i must adjust the mixture screw on the carb?

2) The bike idles at about 1200-1400 rpm, but its a little bit erratic. Is this irregularity a sign of a rich mixture, or should i adjust the idle screw on the carb to allow the bike to idle at 1600-1800?

3) Apon trying to start the bike today, the starter motor turned over twice then stopped, the lights dimmed and the indicators wouldnt flash. I bump started it, and then everything worked fine. I left it running for 5 mins, turned it off, and it then started on the button again. I checked the voltage with a multimeter, and found the resting voltage was 12.02 DCV and the power when running was 12.75 DCV.
Am i right in saying a good battery should hold about 12.5+ when resting, and that the bike is going to fail to start in the morning?

Finally, where is the mixture screw on the carb, and how many turns in or out should i try? I know the idle screw points down out the carb, has a flat screwdriver slot, and has a spring on.

Any help is appreciated, Many Thanks,
Adam

[adamcfc]

Also, there is a white sort of paste over both terminals of the battery, im guessing this is just connection paste or something to prevent corrosion?

[neil.]

Take out the spark plug and if it's sooty/black, chances are you're running rich - this is just to confirm before you start messing with other things. Before you mess with the carb, check the air filter - clean or replace it, as if it's blocked, it will make things run rich. Might as well put a new spark plug in as well - they're cheap.

The white stuff on the battery terminals is most likely silicone grease - it's a very good thing to put over them as it will stop them corroding. Of course, you can use Vaseline or copper grease too if you like. Also it sounds like your battery may be flat - due to it being old/knackered or just flat because the bike hasn't been ridden frequently enough to charge it fully. Do you know how old the battery is? If it's more than a few years old, odds are it's a goner anyway.

[R6 Wilson]

As neil said, check the plug for a rich/lean mixture, maybe refer to this:

https://www.spark-plugs.co.uk/pages/technical/diagnosis.htm ?

How do you mean it is erratic when idling at 12-14? Do you mean struggling a bit or going a bit crazy?
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[ThoughtContro...]

Idle speed for the CBR125 is 1400-1500. 1200 sounds a bit low, turn the idle screw up a bit.

Your battery sounds like it needs a good charge or may be knackered. Fully charged your battery should read around 13.2V. Battery voltage with the engine running and under charge from the charging system should read around 14V.
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"In a world of universal deceit telling the truth is a revolutionary act" - George Orwell

[adamcfc]

[ThoughtContro...]

[neil.]

Plug may also be so fouled up from running rich that it misses the odd spark and so the mixture doesn't ignite sometimes, hence 'missing a beat'. Give it a decent service. 3 months is also long enough for the battery to go flat if it hasn't been on a charger, so take the bike out for an hour or so blast or charge it up with a charger.

[adamcfc]

Okay, took the air filter out, looks a bit grubby but nothing major. The spark plug tip was black, dry fouling by looking at the diagnosis link.

The idle speed it set slightly higher now, although still seems a bit erratic.

How do i make the mixture slightly leaner, is there a picture or diagram of the carb?

Adam

[CarlosCBR]

Does the bike have an aftermarket exhaust? The mixture screw is on the left hand side of the carb.
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[unitynotsocri...]

As other posters sounds like its running rich.If the mixtures are set right and it continues then it might be a choke sticking problem(if it has old style choke)
The battery could be goosed or need a good charge,

backfiring on the overun is usually because of a rich mixture.Unburnt petrol ignites in the exhaust.Hence your sooty plug.

if you fit a charged/new battery and the voltage(when running)is below 13.5 to 14 volt then theres a problem with the voltage regulator or alternator or an earth short from a live wire,Indicators with water in em can cause this fault.

never bother starting up the bike with the headlight on as the battery won't last as long.the extra current stresses the battery more.
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nearly a normal tax paying tosser.......with ferrileness suzi100,cg125,cb125scb100n,cb175,cd100,cj250t,kh250,c15,125 bantam,super 6,rickman gs750,xt500,250rs,dt175,lifan125,dolomite1850,metro,Morris220ld,morrisfg,leyland princess,range rover,corsa,vw camper .now struggling with legs. MORE ORDER = MORE CHAOS

[ThoughtContro...]

Unlikely to be a sticking choke. The choke on the little CBR is pants. If you leave it on after you've started the bike and the engine starts to warm up, as soon as the revs fall back to idle the engine will cut out.

Also he has no choice but to leave the lights on, there is no headlight switch on a CBR125. You switch the ignition on, the lights come on.
____________________
Prize cunt
--
"In a world of universal deceit telling the truth is a revolutionary act" - George Orwell

[unitynotsocri...]

Thanks for info Thought Control,

then its mixtures ,and probably a tired battery.
____________________
nearly a normal tax paying tosser.......with ferrileness suzi100,cg125,cb125scb100n,cb175,cd100,cj250t,kh250,c15,125 bantam,super 6,rickman gs750,xt500,250rs,dt175,lifan125,dolomite1850,metro,Morris220ld,morrisfg,leyland princess,range rover,corsa,vw camper .now struggling with legs. MORE ORDER = MORE CHAOS

[adamcfc]

[adamcfc]

Heres a picture of the bike:


And the Yoshimura system

[ThoughtContro...]

[Clutchy]

[unitynotsocri...]

best way is to test the alternator.

each of the coils,wether alternator or single/simple coils all have a 'resistance.You can measure the resistance and check wether a coil is broken or short circuited.

by removing the alternator connector block you can measure with a multimeter and check against spec.

Bulbs are prone to corrosion at the base and pins and sides.The lead contacts corrode easily and an indicator without a seal on the lense,or a crack soon soaks up water.

I'd check the way the indicators are wired in,as in make sure its standard.An unfused bodged in live feed to an indicator relay could cause power problems if earthed through a soggy indicator.

check the alternator first though,

and if in doubt slap another earth wire from the engine to the frame...........
____________________
nearly a normal tax paying tosser.......with ferrileness suzi100,cg125,cb125scb100n,cb175,cd100,cj250t,kh250,c15,125 bantam,super 6,rickman gs750,xt500,250rs,dt175,lifan125,dolomite1850,metro,Morris220ld,morrisfg,leyland princess,range rover,corsa,vw camper .now struggling with legs. MORE ORDER = MORE CHAOS