Engine running rough

[LoL62 7]

Have just come back from a 1000 mile trip abroad (Assen Moto GP). Whilst there the bike started to run very poorly. The riders I rode with said they could smell petrol when riding behind me. Other symptoms, engine tick over speed has dropped, bike seems to run rich, exhaust note has increased in volume, very poor slow running, engine very hesitant and sounds rough. Where should I start to look for the problem? I only bought the bike in Feb this year? Previous owner had changed the plugs and oil and I have recently synchronised the throttle bodies. It was running fine before I went on the trip. Any advice appreciated

[HornetJay 31]

First check would be to make sure one of the plugs haven't come loose.   But check the fuel lines to make sure there isn't a leak.

 

When you synchronised the throttle bodies did you put everything back properly.

[Maintenanceman 206]

If the fuel pressure regulator starts to leak (gets broken) it will flood one cylinder (if i remember right) by its vacuum hose.

[HornetJay 31]

Good call.

[LoL62 7]

Thanks Henri, would it be easy to see if the pressure regulator is leaking? I have lifted up the tank to have a look for anything obvious. There are no apparent leaks and all the tubes are connected to the underside of the tank etc. I have checked the air filter and that is clean almost new. I know before I got the bike it wasn't, used much although I rode 500 miles or so before the rough running. I was wondering whether the injectors might be contaminated and I am considering using a fuel  additive to see if that helps.Any thoughts?

[HornetJay 31]

I reckon Henri is correct but heres a search on YouTube  

 

 

 

[Kenko 335]

Good find Jason..

[LoL62 7]

Thanks for this Jason and to Henri for pointing me in the right direction. I removed the vacuum tube from the pressure regulator and it was full of fuel so I think I have the answer now. Looks like I need to get a new fuel pressure regulator. I'll update the forum when I have it sorted.

[Maintenanceman 206]

Check out the engine oil as well, there might be fuel also.

[LoL62 7]

I have now fitted a new fuel pressure regulator (FPR) . Fairly straight forward to change

 

First I raised the tank as per the manual and supported the tank up at the front handlebar end to reveal the FPR on the right side of the engine.

I clamped both the return fuel line and the fuel inlet (on the other side of the tank) and put a jar underneath to collect any spilled fuel ( there wasn't much). This is the FPR before removal. The vacuum hose is on the bottom position, already removed (6 O Clock) and the fuel return at 9 O'Clock

 

Remove the old FPR using a adjustable wrench. Once the FPR is taken off its necessary to remove the small tube inside with O rings at either end. I refitted this into the new FPR as the seals were in good condition.

 

Then bolted the new FPR back into place, refitted the return fuel hose and the vacuum hose as below.

 

The bike runs so much better now. The tick over is smooth and the bike picks up from idle as it should do. I have also changed the oil and filter as I think with the bike having run rich it may have contaminated the oil.

 

[Mick 162]

Glad that's sorted, now go and enjoy the bike.

[wayne 426]