Overrun issues and decreased fuel capacity
 

Hi guys,

Multi parter here: 1+2). are similar to the post by lancasterlad and 3). is a general.

1). When slowing down, normally on the approach to TL's or RB's, whether I roll off the throttle and let the engine braking work or favour the brakes, the engine never seems to stop at it's idle, and often actually cuts out completely (even while the bike is still moving)... Yup, the clutch is pulled in before you ask.... This leads to a frantic attempt to restart the bike and me looking rather sheepish :-(


2). Linked to 1) I suppose in that when sat idling, the bike almost seems to cough and splutter, like there's a blockage that's stopping the fuel getting to the engine. It'll run smooth for the majority of the time, but then seems to cut out and just manages (99% of the time) to cut back in recover - I think the needle drops to around 500 before it catches itself. It then shoots to around 1500 rpm, before coming back down to it's normal idle. I've changed the air filter (before and after pics to follow) as some kids tipped it over when it was standing in the car park, but that's not fixed it. I've also twiddled the idle screw so that it was idling at 2k, and still the same behaviour occurred.

I'm currently thinking:
a). Oil change?
b). Sparks are buggered
c). Blocked fuel filter - but it runs fine normally!

Any advice? If it helps, before the air filter change the fuel efficiency dropped to 105-110 till the yellow; replacing air filter has increased it to 115 before yellow... Before I was getting well over 130!


3). While replacing the air filter, I examined the crankcase breather filter. This was covered in oil, which I assume was from the side-age, but when I cleaned it in a mixture of Gunk, Fairy and water it produced a white sludgy gunky stuff, more akin to porridge! This didn't look to right.... Also, there was a large amount of oil actually in the air box, slopping around. The plastic lip surrounding the "mesh fins" on the filter itself was also covered in oil. I thought the oil in the airbox could be from blowing piston rings, but it's only done 14k so it shouldn't do that yet?! As for the stuff surrounding the filter I've no idea.

Thanks for any advice!

Cheers,

Al.

Re: Overrun issues and decreased fuel capacity
 

Is your bike carb'd or fuel injected?

Could be that somethings blocking other parts e.g. fuel lines, air intakes or whatever. If its carb'd, it could be worth checking that the needles are not blocked? I don't really know, but it sounds like something is blocked

Matt

Re: Overrun issues and decreased fuel capacity
 

Injected.

Glad I'm not the only one! It's really got me baffled.

Re: Overrun issues and decreased fuel capacity
 

i get a good 110 outta a tank before yellow on my 00' curvy. its running a fuel exhaust and i think a renegade air folter. but i rag the ****e outta it everywhere :-)

Re: Overrun issues and decreased fuel capacity
 

Heh I got a standard stock everything and (currently) can't rag it everywhere! I followed a Gixxer 6R on the way to work along the twisty roads yesterday, and the light was on at 90 :(

.... but he didn't lose me!

Re: Overrun issues and decreased fuel capacity
 

Best get the bike to a dealer, or someone who can plug in a computer and check the fuelling. It could be running rich - maybe a sensor is not working properly, making the FI put in more fuel?

Matt

Re: Overrun issues and decreased fuel capacity
 

I used to have a similair stumble at idle thing, which was caused by being very rich in the low end- it'd flood a little, then recover, sometimes it'd stall. But that was a carbed model... I suppose the same could occur with the FI but I don't know why it would.

Re: Overrun issues and decreased fuel capacity
 

it's a computer, it doesn't need a good reason...;)

Re: Overrun issues and decreased fuel capacity
 

OK I'll start with point 3:

If there's oil proper sloshing round in the air box this isn't right, it's almost certainly come up the breather pipes and possibly done that after the kids kicked it over. I would not be worried about piston rings. Clean it out with a cloth or rag. It's usual to have a bit in there though....

The mesh filter thing on top of the breather pipes is always oily, don't worry about it, the excess will drip back down the breathers to the crank. Using a de-greaser such as "gunk" will form an emulsion with the oil and give you your porridge stuff. You don't need to clean it, so again, No worries.

Check your oil level is correct, with the bike upright and the engine off the level should be between upper and lower using the right hand side sight glass. There's a nice bright silver shiny plate about 5mm behind the glass so if all you see is black it's over filled, if all you see is silver it's too low.

1 & 2 may be due to oil from the airbox getting into the intakes (though this is not necessarily right) or may mean the bike just needs a good service, if the air filter was black and you've not mentioned a routine service I'd be looking at balancing the throttle bodies, checking, cleaning, and gapping the plugs and checking everything's moving smoothly.

HTH

Jambo

Re: Overrun issues and decreased fuel capacity
 

Sounds like it's running rich. Does it behave better when the engine's cold than when it's warmed up?