Exhaust fumes smell like petrol

Hey guys, I've got an interesting situation on my 99 VFR800. Recently the exhaust fumes have started giving off a petrol smell. It's been hot lately when riding it, constant bike tempt between 90-104 degrees whilst riding and it's then when the smell is present. Can only tell when I'm stationary though but doesn't smell when the bike is switched off or before running.
Can't smell the petrol other than at the exhaust, just wondering if this may be something sinister or something to do with venting?
The bike is is just about to go for its 24,000km valve clearance service so it's still a baby, other than this its extremely good condition.
Any help appreciated
Cheers

 

I have nothing useful to offer BUT... wire a spark plug to the exhaust and see what happens. Take video.

 

Is it getting cold and boring in Ottawa? Get out and skate the Rideau Canal for me!

 

One cause for rich running would be a faulty fuel pressure regulator or a perforated vacuum hose leading to the regulator. If you pull the small vacuum hose off the regulator, it should be empty and dry. If it contains any fuel, the regulator may have perished allowing fuel to pass through into the vacuum line into the intake.

 

Did you mess with your PAIR valves?

 

I second this. It is a common fault in cars.

 

I've just checked the plugs for signs of incomplete combustion, they look fine.
Pair valves haven't been touched to my knowledge and I doubt they were in the 10,000km before I owned it.
I'm about to take the tank of and check the pressure reg/breather hose.
Thanks for the help so far

 

Just got the bike back together.
Found petrol residue inside the air filter housing. It's come back through the crankcase breather and splashed up around cyclinder 3's air inlet funnel.
Cleaned all the residue off and took it out. Didn't smell like unburnt petrol.
Unsure why this would happen though, any ideas?
I Do remember that on the last fill up I slightly overfilled but I doubt that would affect this.
didnt bother taking the air box off after this though since it was getting late.
Anyone got any ideas as to why fuel would come back through the breather?

 

I think that's oil, not fuel. If you overfill on oil I think it will go through the crankcase breather. Are you sure the exhaust don't smell of burned oil, and not of unburned fuel?

Or the oil might smell of fuel, and then you may have some other issue (like a leaking fuel injector for example). That fuel will go into the crankcase, and out the breather hose when the engine gets hot.

 

I'm really interested in the outcome of this thread btw, since I also have a similar issue. So please post when you find the cause of your problem.

 

Done some more sussing around, i doubt it was fuel in the air box. Oil doesn't smell of fuel at all and I understand it should if it came through the crankcase breather. Ive haven't got time to work on it myself before i go away for 4 days riding so off to the mech it goes ( $$$ grrr ). Hopefully they figure it out and its nothing more than running rich somehow.
SweViffer, ill update this thread when i know more.

 

A little bit of oil residue in the airbox is perfectly normal; you will get a bit of oil mist making its way out of the crankcases when the engine is revving hard. No doubt a high oil level would make that worse but a few drips would be normal and unrelated to your concerns about rich running,

 

Is the manual enrichment circuit (choke) fully closing at the throttle body?

 

rIDERS who sniff their tailpipes, omg, PLEASE !! :crazy: A Bob Dylan song if in meremember. :uncomfortableness: