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

[Mississippi Bullfrog]

Did you clean the tank out? Also check the fuel vacuum valve. If that isn't working you'll get fuel starvation.

If it was running fine when you picked it up I'd suspect it's a fuelling issue.

[skyrider]

take it back and bend their ear about it

[Guest Richzx6r]

Definitely sounds like fuel starvation, maybe some crud has got in to your jets and is causing a slight blockage though I'd try the easier stuff first as mb has said

[fastbob]

take it back and bend their ear about it

 

Surely they will just say it was alright when they sold it and it dosen't work after you tried to fix it . I'd be putting a bit of spit on the downpipes to see which one is running cold and take it from there .

[ThePhatomfart]

AS all above , but pop your spark plugs out to see what colour they are , that is Black sooted or White

[TimR]

As it runs ok at stand still i would check that the side stand switch is not sticking in its "stand down position" when the stand is raised .

This can happen if its been left on stand for a prolonged period of time abd cause a partial cut off to engine and produce these effects .

[TimR]

Also check battery connections if you were not the one to replace battery

[Grumpy Old Git]

Did you clean the tank out? Also check the fuel vacuum valve. If that isn't working you'll get fuel starvation.

If it was running fine when you picked it up I'd suspect it's a fuelling issue.

 

As above - Have you checked the fuel filter (may be inside the tank)? also, check the air filters are clean.

Have you tried running it with the fuel cap off? If that cures it, you have a blocked breather.

I would not start looking at electrics / battery until i had looked at all the fuel / air possible faults.

[fastbob]

Kinked vacuum hose ? Try running on prime .