Limited to < 4000rpm
 

Hi guys,

I bought an F4 in August and had carb problems as it had been stood for 18 months. I've since replaced the carbs with some clean ones and done a lot of work on her. However since riding for the first time on the open roads, I'm limited to about 3000-4000rpm in 1st/2nd gear :-S

I've had her on the centre stand and ridden with the rear wheel unloaded and there isn't a problem, she revs nicely through the range in all gears.

Can anyone make any suggestions to what I can check/replace?

Thanks,

Howard

What do you mean by limited, does the bike cut out? Or does it sputter and die like it was being starved of fuel or air.

Sounds like a fuel delivery problem. I'd replace the fuel filter and clean the tank. Could be the plugs too...

The bike doesn't cut out at 3000-4000rpm it just doesn't respond to any increase in throttle. It feels like it is being starved of fuel.

The air filter, fuel filter and spark plugs have been replaced, the tank has been flushed out multiple times and the strainer looks fine.

The new carbs haven't been synchronised but the pilot screws have been adjusted to specified number of turns in the manual.

Do you think the fuel pump is on it's way out?

You replaced the carbs with "clean" ones? Were they freshly rebuilt? Sounds like they may be plugged up a bit, or not jetted properly. Double check the vacuum lines and intake boots to ensure they are not leaking. Maybe put the choke on a bit and see if it runs any better. That would point to a vacuum leak leaning the mixture out to the point of power loss.

Pull the plugs and see if they are in good shape or not. The spark plugs will tell the A/F mixture story.

Thanks for the advice Demon. I've tried the choke and it momentarily gives an increase in power and then returns to it's laboured/starved state. I'll take another look at the vacuum lines and boots for any leaks. I'm just not sure why it runs OK on the centre stand, is that because there's no load on rear wheel?