not running well.......

Hi all, i have a 1998 cb500 and having dificulty keeping revs down, when reved it will stay at that rev for a while and then back down very slowly, engine is getting hot rapidly and bike not accelerating as normal.........so I have just stripped and cleaned carbs and renewed air filter, plugs had a slight carbon deposit but nothing too serious. will attempt balancing carbs tomorrow.........not to sure on air fuel mixture screw yet...ANY IDEAS..............any info supplied would be greatfully recieved.......

Hi mate,

Is the throttle cable sticking or the linkage on the carbs all gunked up restricting movement in its operation ?

Does the throttle on handlebar operate freely and return back to its shut-off position when you let go?

I would make sure of this first because if the butterflys are not operating smoothly because of sticky throttle cable and or mechanism then its not going to accelerate/decelerate smoothly.

Also check air/vacuum hoses too for splits as this could be affecting mixture resulting in your carbon coloured plugs, If all is ok then yeah your running a little rich and adjust accordingly or maybe its the wrong type plug.

I would check this first before balancing carbs as everything needs to be in good working order prior to doing this.



Temperature, whats the idle set at as high running will heat it up quicker and does the radiator fan kick in when the temp gauge goes so far.

Check coolant levels and also check its not all emulsified and gungy....if so it will need flushed and new coolant added at the right mixture as this will help temps as well as preventing corrosion internally.

erm...just a quicky here as t-breaks are short and sweet where i am....lol


hope this help ya a bit

Cheers mate, have cleaned the linkages and checked the cables....I did find the air/fuel mixture screw was only 1/2 turn from the stop, have reset at 1 1/2 turns and running much better. Topped up the coolant as was a little low, all back to normal again....thanks for advise

Was a sticky throttle cable/mechanism the cause then ?

Just check plugs again after a good run and it will give you an indication if you got the mixture as near as damn it, also watch when putting the plugs in with the extension bar and spark plug socket. I found my socket had to much grip and when I had torqued the plug back in and tried to remove the bar the socket stayed in place....lol.

I then tried to just grip it and no more but plug fell in and knackered the electrode gap......reset it but got there in the end

When cleaning the carbs there was a lot of debris i the float boals, also one of the float needles was not hooked on to the float. When i reasembled it i noticed the mixture screwes were too far in, seems to be running very nicely now, i lubed the cables but they lookeed in resonable condition and moved freely. It is running alot better now.....p.s I have only just picked this bike up, bought it as a runner, just..........just a couple more things to sort.