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vacuum tap issue
Posted: Sun Jul 15, 2018 2:33 pm
Author: dave cullen
Anybody come across this before, I had a pool of petrol under my ELR this morning and was cursing my new carbs till I saw it was dripping out the air box, and suspected the vacuum tap had failed, it was on reserve position.
I put some more fuel in it, (after checking I didn't have cylinders full of petrol!) switched tap to ON, and it was running fine, stopped engine, unscrewed a drain screw, and flow had stopped as it should, but when I moved it back to reserve, it started to flow again!
It's like the tap has partially failed??
Any thoughts appreciated
Dave
Re: vacuum tap issue
Posted: Sun Jul 15, 2018 5:20 pm
Author: z1bman
i don't think the reserve side of the tap doesn't run off vacuum
Re: vacuum tap issue
Posted: Sun Jul 15, 2018 6:25 pm
Author: dave cullen
z1bman wrote:i don't think the reserve side of the tap doesn't run off vacuum
just me being stupid with too much lager after football, does that mean when tap on reserve, fuel flows all the time whether engine running or not??
Re: vacuum tap issue
Posted: Sun Jul 15, 2018 6:55 pm
Author: DavidZ1R
Reserve and prime are both unrestricted flow.
Re: vacuum tap issue
Posted: Sun Jul 15, 2018 7:56 pm
Author: dave cullen
DavidZ1R wrote:Reserve and prime are both unrestricted flow.
I feel so stupid David, I had no idea that was the case, I am so grateful to you and Z1B man for your help, my only excuse is I rarely run onto reserve and obviously the bike shop had to do so during the dyno test.
Many thanks
Dave
Re: vacuum tap issue
Posted: Sun Jul 15, 2018 9:07 pm
Author: DavidZ1R
Just check your overflow tubes are clear, the petrol should come from them not the air box, just blow in each one see if they are clear.
Re: vacuum tap issue
Posted: Thu Jul 19, 2018 11:29 pm
Author: needaz1100r
dave cullen wrote:DavidZ1R wrote:Reserve and prime are both unrestricted flow.
I feel so stupid David, I had no idea that was the case, I am so grateful to you and Z1B man for your help, my only excuse is I rarely run onto reserve and obviously the bike shop had to do so during the dyno test.
Many thanks
Dave
Nor me, every day is a school day, but....
even on prime or reserve with no vacuum control, there should be no fuel leak, the carbs should hold the fuel back via the float needles. Petrol shouldn't be running anywhere, neither from overflows nor the airbox.
Re: vacuum tap issue
Posted: Fri Jul 20, 2018 8:06 am
Author: Charlie
Reserve DOES run on vacuum, (otherwise there would be no point in having a prime function).
If anyone's tap IS running free on reserve - they have an issue with the tap diaphragm. You should be able to pull the fuel hose off the tap with no leaks from the tap in any position bar Prime.
Dont believe me ? Fit an inline clear filter and watch it.
If fuel is running out the vents, the most common cause is dirt in the fuel not letting the float needles seat properly ( inline filter time), then it's sticking floats (tap the bowl with a screwdriver head and they usually stop leaking), badly set or leaking floats, and then worn needle or seats.
They should not leak even if the tap IS on Prime.
Re: vacuum tap issue
Posted: Fri Jul 20, 2018 1:33 pm
Author: PAULJAC47
Zeds if have owned with vac taps,have only flowed all the time with tap on prime,res and main vac operated.
Re: vacuum tap issue
Posted: Fri Jul 20, 2018 2:00 pm
Author: Charlie
I would suspect there was an issue. None of my bikes flows on reserve unless the motor is running. They should not free flow on anything but Prime on a vac tap.
Re: vacuum tap issue
Posted: Fri Jul 20, 2018 2:24 pm
Author: needaz1100r
Charlie wrote:Reserve DOES run on vacuum, (otherwise there would be no point in having a prime function).
If anyone's tap IS running free on reserve - they have an issue with the tap diaphragm.
This is what I thought to be true. You should be able to pull the fuel hose off the tap with no leaks from the tap in any position bar Prime.
Dont believe me ? Fit an inline clear filter and watch it.
If fuel is running out the vents, the most common cause is dirt in the fuel not letting the float needles seat properly ( inline filter time), then it's sticking floats (tap the bowl with a screwdriver head and they usually stop leaking), badly set or leaking floats, and then worn needle or seats.
They should not leak even if the tap IS on Prime.
Agreed 100%