CBF500 general loss of power across rev range

[lmcbf500]

Hello all.

Need your help with an issue on a CBF500 2006 which I bought recently.

It had low miles and when I drove it home the bike was fine. Close to home it started running rough - low power (would not go up steep hills for example). The bike had sat for extended periods of time. On getting home it had a rough idle.

The petrol smelled off like paint thinners and a bad colour so thinking it was probably off-fuel I drained the tank and cleaned the carbs and jets out.

Put the bike back together and she now idles good and revs smooth at standstill and I can rev to the redline but on the move has a general lack of power (comparing against an identical bike of my friends). In low gears the throttle should be urgent and it accelerates at maybe half the rate it should. In higher gears it might only get to 5 or 6k revs due to the lack of power. Bike still feels like it is running smooth, just under powered.

I have also replaced plugs, checked stator voltages and checked regulator. The bike had a new battery fitted also.

Anyone have any ideas based on my symptoms? Forget what I have done/checked - based on my symptoms what do you guys think the issue might be or where should I start to troubleshoot?

Thanks in advance

[Nobby the Bastard]

When starting from cold do all the exhaust headers get scalding hot virtually immediately?
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trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050

[lmcbf500]

[Nobby the Bastard]

Yes, they should.

They should be scalding hot within a couple of seconds of the bike starting. If any one taks noticably longer than that then that cylinder probably isn't firing.
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050

[lmcbf500]

[stinkwheel]

If a 50bhp, twin cylinder bike can't go up a steep hill, running on one cylinder would be my first suspicion too.

So I'd check it's running on two and if it isn't, I'd check for a spark on the dead side first-off.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[lmcbf500]

[jaffa90]

"""""The petrol smelled off like paint thinners and a bad colour so thinking it was probably off-fuel I drained the tank and cleaned the carbs and jets out.""""

If you didn`t clean the tank out like the 6 carb jets did you fit an inline fuel filter?

[lmcbf500]

[Pete.]

If the vent tube is not blocked that's all that counts. Do the check that Nobby suggests, use a wet cloth to see. Once it's been running for 20 seconds wipe the cloth quickly on the headers and you'll see it evaporate immediately.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Nobby the Bastard]

It's working and then suddenly stops working it's not the fuel. It could be crap in the tank blocking jets but that's relatively rare.

Almost every fault turns out to be electrical so I'd really be starting there after finding out one of your cylinders isn't working (which it isn't, the hotness test is just to prove it before we go any further)
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050

[Easy-X]

[Nobby the Bastard]

[lmcbf500]

Ok guys both downpipes very hot after 20 seconds and sounds fine as first thought.

What next?

She revs sweet as a nut at idle. Just run her up to temp now.

[Easy-X]

So what's left?

Not enough fuel, not enough airflow, slight loss of compression, timing issues? Bet it's one of those
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Royal Enfield Continental GT 535, Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[lmcbf500]

Yea exactly

I’ve only ever had FI bikes so carbs are a mystery to me when it comes to troubleshooting. That’s why I’m asking on here the common things I should start with after cleaning them out.

[2wheelLover51]

The brakes aren't binding are they? First thing I'd do is whip out the plugs to check for condition and the colour to gauge if the mixture (fuel/air ratio) is as it should be. Plugs should be a light tan, or a bit lighter. If they're all sooty or oily it would indicate running too rich or worn rings/piston. A compression test would also be a good idea, low readings indicating badly sealing valves.
Since the bikes running smoothly low compression from some cause would result in the lack of power you're talking about.
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2WHEElLover1951

[lmcbf500]

[Pete.]

Have a look at the air filter. I've seen them so clogged a bike wouldn't rev.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[lmcbf500]

[Tdibs]

I would twist off the ht lead caps and inspect/look for any cracking in the lead, or any corrosion on the bare wire, even pin hole cracks can still arc. Having it idle fine, then dropping a cylinder when you give it some welly sounds a lot like a bad ht lead. If no dice then I would pull the carbs and go from there.

Also worth checking the fuel line has no kinks/hard corners if you have had the tank on and off.

Is there a notice change in tone when it loses power? feel more vibey?
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Previous : 09 Vanvan 125| 02' Sv650s || Current: 1999 Xj600n | 1992 DR650 RSE | 2005 Fazer 1000

[lmcbf500]

[lmcbf500]

[jaffa90]

A white tipped plug is a lean burn, oily threads only, sounds strange if no external oil when removing them.
Sooty cans sounds like shit fuel / starting engine and not riding it.

[lmcbf500]