CBR 125-RW6 Won't idle or run for long before stalling

[CBromyard]

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 dyno 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

[Fisty]

Return it to standard.
____________________
Quietly and consistently taking the piss.
TL1000R | Hayabusa | ZXR400 | TL1000S | Bandit 400 V
Fatter and faster than Fret

[bikenut]

sounds like a fuel problem.....good sustained fuel flow from tank to an outside reservoir like a 2 litre pop bottle.......should fill the 2 litre bottle in about 2 minutes??

try that but be carefull of fire risk.......does the fuel "hang" or flow slow down and stop after 2 mins ish? I presume there is plently of fuel in the tank ( 3/4 full ) ??

did yopu buy this bike from a dealer and its under guarantee??
____________________
nuts about bikes

[CBromyard]

Fuel slow seems ok. Vacuum hose definitely works as with suction it pulls it through.

Took the carb off and gave everything a good clean. Removed main and pilot jets, no blockages. Now it won't start at all...

Sadly bought it privately. Booked in to see a mechanic but rather cut the two week wait and cost if I can get it running myself

[Fisty]

[cb1rocket]

2nd that, fit standard carb
____________________
Honda H100S2 Rebuild - https://www.bikechatforums.com/viewtopic.php?t=253852

[temeluchus]

returning it to standard is your best option.

Too large a carb will be far more trouble than its worth, it will never likely give you much more power and will not run as well most of the time even if you spent the time getting it running.
____________________
Some shite cruiser. Now with guns and FREEDOM!

[Northern Monkey]

Have you tried returning it to standard?
____________________
Fisty: after polishing the tank with the glistenng beads of sweat from my full hot scrotum, I filled the headrace bearings with 10cc of my manmilk

[mentalboy]

Is the bike running an oversized piston and pot? It seems an odd thing to fit a large bore carb without running on a larger piston.
Whilst I agree with the 'return to standard' posts I'd hesitate to spend any more money throwing parts at it without making sure you've found the source of the problem - you are probably well on your way to spending more on the bike than it will ever be worth.
____________________
Make mine a Corona.

[Nemo]

Im in the standardize it column.

Could be float height, jetting, mixture, float valve.....
____________________
Previously owned: Kawasaki KH125, Suzuki GP125, Suzuki GX 125, Honda CB125 TDC '83, Honda ntv 600, Kawasaki ER5, Kawasaki ZZR600, Aprilia RSV 1000 Mille
Now own: Ducati 848 evo

[reckless_b]

could be silly question, have you got a spark now?
did it start back up when it used to run, straight away or after some time?
____________________
40 years on the road on and sometimes off bikes with a very recent OFF

[salem1987]

Try having the fuel off and carb empty and fire the bike up with a small bit of fuel poured down the spark plug hole. If it fires then you know its probably a fueling issue.

Also with it all back on, try running with airbox off completly. Then vary the choke till it hopefully runs. Should give you an idea on jetting. If it fires itself up nice without the box and no choke its probably too rich.

These are just things ive had to do on my cb250rs i got that wouldnt fire up and had a very black spark plug. Turns out if i run it without the cheap cone airfilter its spot on, lowered the needle and jetting and its fine.

(someone had done some "tuning")

Intake manifold ok? no splits in it?

[moonzoomer]

Check that valve clearances are not too tight, i.e valves not sealing when bike has warmed up.

[Stalk]

Does it have a fuel filter fitted? If so it may be overly restricting the fuel flow as it is a gravity feed. Had the same problem with aanother bike and it would effectively run out of fuel. If so, try removing it. I know its a bit of a long shot but you never know

[CBromyard]

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. No fuel filter. Good 1/4 + reserve in fuel. 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.

[mentalboy]

Oil or petrol on the end of the spark plug?
Petrol is a good sign, oil is not
____________________
Make mine a Corona.

[CBromyard]

I'd have to say it's very small amount of oil

[mentalboy]

[CBromyard]

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.

[mentalboy]

[CBromyard]

If excess fuel is in the engine, would this mix with the oil? I don't see how running through new engine oil would get rid of flooding?

Cheers

[Copycat73]

[mentalboy]