vfr400 nc24 issue

[enzo]

hi all just after a bit of help/ideas with a problem iam having with my vfr.
i have had a mis, mainly higher up in the rev range for a couple of weeks so i thought i start the process of elimination off with draining the fuel tank and putting some 96 fuel in it.
when i put it all back together i notice that the fuel tap diaphragm has
- inlet from tank to tap which has filter on it.
- and outlet from tap to a tee that feeds carbs i imagine.
- 2 other small nipples that i can only imagine are some sort of vacumn device, 1 of the nipples has a small hose that goes to the top left hand side of the head, the other nipple looks like its completly missing the hose?
iam wondering where the other nipple is supposed to run to.

iam also having a problem where iam driving along going through the gears then all of a sudden at about 80kmh and above she looses all power and stalls while still rolling along the road,
ive read other forums with similar problems to mine and a few things keep coming up
-exhaust packing
-vacumn in tap diaphragm (what i imagine could be those nipples i was talking about.

anyhelp with this would be great as iam a bit stuck at the mo.
cheers in advance

[el_scor_cho]

i think the tap your talkin about is the breather. it just hangs down. the other pipe that runs up the side is the vaccum tube that sucks the diaphram out.
i had a similar problem and after 100s of my hard earned monies spent on locating the problem i found that my entire tap was broken and only letting a small amount of gas in rather than being completely open.
have a look at this but other solutions i came across on my hunt is the possibility that the tank can be sitting on either the vaccum tube or the fuel lines.
also bypassing the diaphram if your vaccum is farked is easily done. have a gander on the google machine if all else fails. easy to reverse too

[glegge]

spark plugs? not saying yours are, but they are often overlooked (esp with modern ignition systems that keep them firing under the worst conditions), but they are often the cause of many problems. although mostly you will notice poor starting, but they could be the cause of a miss 'under load' or such like.
funny, it must the the time for vfr400 vacuum fuel taps to fail, recently fixed a mates one in palmy, the diaphragm had a hole in it, so it's all bypassed now. something to watch for though, make sure you put the vacuum hose on the correct fitting (nipple), if you put it on the vent, and the rubber diaphragm fails, you'll fill your crank case up with fuel (dont ask me how i know this). but yeah, if it's shutting down at speed then coming back on power, it may be a fuel starving issue. is there a fuel filter? checked it's not blocked?

[road king]

i had a similar problem with my old aprillia, the breather hole for the fuel tank was blocked. tri going for a ride with the filler cap off

[road king]

had a look in my service manual, hasn't got much in there about the hoses to and from the fuel tap. but it sounds about right for the mystery nipple to be a breather.

[glegge]

having recently worked on one of these, i can confirm, there is two nipples, one for vac to intake port, the other is a breather and has nothing connected. from memory its the outer most one that has the vac applied (put memory hazy at best of times)

[enzo]

righto. i replaced hose from tap to inlet manifold seems to be working sweet again. have just got to diagnose slight miss/flatspot now
CHEERS VERY MUCH FELLAS

[enzo]

just been for a long ride to make sure its all ok...
but unfortunatly not.
after about 20 minutes of riding (sensibly) the bike virtually switched off, not quite but it lost all fire power, as soon as i took hand off throttlle it died, put hand back on and all i got was burrrrrrrrrrrrr?????????
got me fuuuuked.
may try bipass the diagphram idea tommorow but i just dont know what going on.
anyother ideas guys????????

[hayd3n]

just been for a long ride to make sure its all ok...
but unfortunatly not.
after about 20 minutes of riding (sensibly) the bike virtually switched off, not quite but it lost all fire power, as soon as i took hand off throttlle it died, put hand back on and all i got was burrrrrrrrrrrrr?????????
got me fuuuuked.
may try bipass the diagphram idea tommorow but i just dont know what going on.
anyother ideas guys????????

check ur fuel filter

[el_scor_cho]

sounds exactly like my problem. bike starts to gurgle and loose all power, upon pullin over she cuts out. after about 5mins all good to go again.

when bypassing whip your tap off and make sure when in the on position its pumping out enough. mine looked all good to the untrained eye so i disregarded it, get someone who would know if its being restricted or not to have a gander at it. all the best

[road king]

did you try riding with your filler cap open?

[enzo]

sounds exactly like my problem. bike starts to gurgle and loose all power, upon pullin over she cuts out. after about 5mins all good to go again.

when bypassing whip your tap off and make sure when in the on position its pumping out enough. mine looked all good to the untrained eye so i disregarded it, get someone who would know if its being restricted or not to have a gander at it. all the best

thats exactly what it did 1 ciggarette later she started i drove home a further 10 mins and didnt fail again.
yea looks like pumping enough just realised that my off posision on tap isnt working it doesnt turn off flow.
can i ask what you did to yours to fix problem?? cheers

[enzo]

did you try riding with your filler cap open?

yea man tryed that tank has a breather on top aswell.

[el_scor_cho]

thats exactly what it did 1 ciggarette later she started i drove home a further 10 mins and didnt fail again.
yea looks like pumping enough just realised that my off posision on tap isnt working it doesnt turn off flow.
can i ask what you did to yours to fix problem?? cheers

i was lucky the local mechanic stumbled across it during a service. he foudn out that if i position the tap a small click between off and reserve she flowed smoothly.
I never sussed out a new tap as i passed the bike on soon after (yes informing the new owner) but off the top of my head they arent pricy

[enzo]

i was lucky the local mechanic stumbled across it during a service. he foudn out that if i position the tap a small click between off and reserve she flowed smoothly.
I never sussed out a new tap as i passed the bike on soon after (yes informing the new owner) but off the top of my head they arent pricy

nice. cheers fa that. was thinking could this be an electrical things. long shot i know just had a feeling that all