Bike cuts out under load?

[ducatilover]

they wouldn't have fitted anti-desiling solinoids would they? surely not
that would be funny.
those are a bastard to diagnose without replaceing and would be controled by the CDI unit. check the electrical conectors for dirt and moisture

Oh God, you just ruined my night.

Off to google again...

[Lus7]

The vacuum tube could be fine.
It may still work, but not flow as much as the engine needs if it's split.
If it's soft, it'll close up and stop vacuum supply to the pump.

yeah, i'll replace it.
But even still, that doesn't really account for why the issue only happens when the tank's below half

[ducatilover]

they wouldn't have fitted anti-desiling solinoids would they? surely not
that would be funny.
those are a bastard to diagnose without replaceing and would be controled by the CDI unit. check the electrical conectors for dirt and moisture

Seems to have Mikuni BDS26s fitted to it, I'm not sure if they had an anti run-on solenoid?

yeah, i'll replace it.
But even still, that doesn't really account for why the issue only happens when the tank's below half

Unless the weight of the fuel in the tank is enough to push past the diaphragm in the pump
In which case, the spring behind the diaphragm may be weak.

[mellowyellow]

is the following correct?
Your bike is a 2006 yamaha VX250 which has only done 14,000 km's
all you have done (or has been done) to the bike is
* change the plugs
*oil change
*drilled some holes into the muffler
*the air box is removed and a pod filter installed, this has left a couple of hoses to flap about without a home.

things to check so far...... correct oil level, correct plugs, reinstall the air box so the hoses have a home for now.

so, bike runs okay (though lacks power) until its running high revs up a hill. when fault happens, engine wont start unless full choke is applied and turned off once started.
are you sure the oil level is correct? (Make sure that the motorcycle is positioned straight up when checking the oil level. A slight tilt to the side can result in a false reading)

firstly, this is a V twin with single carb, applying full choke to the makuni bypasses the throttle piston, draws lots of fuel from the float bowl and dumps the atomised fuel behind the throttle piston. this could be an important fact to note. full choke applies vacuum to the float bowl. (dont worry about the choke not being needed when you cold start, its not really a choke, just a fuel enrichment system, doesn't "choke" the engine).
so, it seems your float bowl is empty at the time of the fault, hence the reason why full choke remedies the fault.
what causes the float bowl to become empty? starting from the carby....
*sticky float (wont drop to let in fuel)
*sticky needle valve
*pressureised float bowl (vent plugged where it shouldnt be or not attached)
*no fuel getting to carby

so lets look at the no fuel geting to carby possibility
starting from the tank.
*the tank needs to have fuel in it
*the fuel tube in the tank needs to be clear, no crap floating in the tank, just waiting for its time to block the tube
*the fuel tap apparently filters the fuel, find out how to clean it
*the fuel tap has three settings, one of which is vacuum opperated "on", set it to "primary" incase the diaphram is needing to be replaced.
is the tap leaking? is it leaking fuel out the vacuum hose? does the hose have a hole in it?
*next is the vacuum operated fuel pump, this too could have diaphram issues or loss of vacuum due to clogged lines or cracks in hoses.
*lastly is the path to the carby. there will be a fuel filter canister somewhere, check its condition. more than likely there will be a second filter just inside the carby.
the whole fuel delivery system relies on vacuum, without it, it may take 20min for the fuel to trickle down from the tank and fill the float bowl. applying full choke would "suck" the fuel into the float bowl.



first thing (after rechecking oil level and reinstalling the airbox) i suggest is to inspect the float bowl breather. is there crap in the hose, could crap have gone into the hose and into the float bowl? if so, have the carbi serviced.
second thing, clean the tank, really shake it about with some fuel in it and make sure nothing is floating around in there.
third, create the fault and carefully disconnect the fuel hose where it goes into the carby. allow about 500ml of fuel to drain into a CLEAN 1 litre container this is to see how fast it runs out with bike off. i would expect it to rush out at first (as the pipes empty), then trickle out.
with hose still in the bottle, hit the starter, how fast is the fuel pumping out? is it pumping out? if so, then you have no issues with fuel delivery. reconnect the fuel hose to the carbi and try to restart the bike, still nothing? choke it, still nothing? choke and half throttle.

if the fuel delivery test fine, the carby could be full of sludge, have the carby serviced

[ducatilover]

I forgot about the pod.
Put the airbox back on

[Lus7]

So far this morning I have learnt how to take the tank off, access the carb, understand how everything connects/works together and replaced a whole bunch of tubes.
Here's a video:
http://youtu.be/TT0Bux-nQfQ

I forgot about the pod.
Put the airbox back on

haha nah I never got round to putting a pod on it, just replaced the air filter with a stock one

What I've done so far:
* changed the plugs
* oil change - 10w 40 car oil
* drilled some holes into the muffler - plugged them up with bits of cork
* changed the air filter with another stock sponge one
* Replaced all the tubes but the two going from the tank to the tap with fuel line hoses from supercheap

I'm a little concerned about the tube connecting to the fuel pump. at 0:18 of that video, the tube seems to be bent a little too much, worried it could restrict vacuum flow - but it doesn't seem to

Also my engine seems to be knocking a little, is that normal? You can kind of hear it in the video, it's done that for ages and i've just ignored it.


I just took my bike for a ride (full tank/changed tubes) and it seemed to ride smoother. Not entirely sure though.
Syphoned 5L (out of 15) of the tank into a gas can and took it for another spin, rides a little better than I was expecting. Seemed to do mini chokes every now and then but i'm not sure if that's just placebo or bumps on the road.

Gonna ride it round till the tank runs low today in an attempt to get the bike to break down again. will report back.

[p.dath]

Hold on - you used car oil?

[GSF]

* oil change - 10w 40 car oil

If you start noticing the clutch slipping a bit, this might be why.

Also, it'd be interesting if the bits of cork you stuffed into your muffler get hot enough to start burning.

[mellowyellow]

the wires going to the carby are probably nothing more than a carby heater to help atomise the fuel when cold, some bs like that anyway.
failing that, they could be just grounding wires. either way, nothing to worry about.

so, back to the oil, definitly not over filled? that would cause you to loose power too, as well as a whole lot of other bad stuff. using car oil aint too good for the bike. i dont know enough about bike clutches to know if car oil additives slowly soak into the plates and screw em over for good or not. might be something worth finding out.
i know oil on a car clutch is bad, no matter the grade or type

edit; i may be wrong, but.....your fuel tap should be horizontal, not vertical, to select primary. if the fault occurs, switch it to primary

[Lus7]

Cool so that fixed nothing.

Tried riding with the cap on, off pri etc. even after replacing the lines it's still stalling. ghey as bro

[Lus7]

On the plus, it seems to last longer and breakdown for shorter periods of time. Don't know if that has anything to do with anything though

[ducatilover]

Did you try the clear tube/carb bowl when it cuts out?
What a cunt of a problem.

[Lus7]

Did you try the clear tube/carb bowl when it cuts out?
What a cunt of a problem.

Nah, forgot it at home.
I'll try that tomorrow, maybe the bike is fine, i just need to keep the tank above 1/2 full.

Know if the biker meet ups are still going on in albany on weds?

[ducatilover]

Nah, forgot it at home.
I'll try that tomorrow, maybe the bike is fine, i just need to keep the tank above 1/2 full.

Know if the biker meet ups are still going on in albany on weds?

Does it do it when it's on the reserve or prime position? (sorry if I have a weak memory, Kawasaki ownership does odd things to a man)

No idea about Albany, I'm about 5-600km south of that...

[mellowyellow]

Cool so that fixed nothing.

Tried riding with the cap on, off pri etc. even after replacing the lines it's still stalling. ghey as bro

yeah ducatilover, he has tried prime. hard to keep up with what has and hasn't been done with this one
try the clear hose, be interesting to see if the carby has fuel in it when it stalls out.
replacing the hose is good, atleast it removes that from the list of possabilities.

not really much more you can do until you find out if theres fuel in the float bowl when it stalls and if the fuel is pumping after it stalls.
trying the above with a 1/4 full tank is probably best. i'm thinking the weight of the fuel in a full tank is the only thing reducing the stall rate and down time.