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Aprilia RS 125 fuel not flowing into engine!

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SilverFriends...
L Plate Warrior



Joined: 21 Apr 2020
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PostPosted: 17:44 - 21 Apr 2020    Post subject: Aprilia RS 125 fuel not flowing into engine! Reply with quote
The motorcycle has been sat for about 6 months without being started. It appeared to be functioning normally before this.

The problem seems to be that fuel is not flowing down the fuel line into the engine from the tank.

Here is what I tried: I removed the vacuum line from the engine block leaving it attached to the fuel tank. I also left the fuel line attached. I sucked on the vacuum line then attempted to start the bike. It started and ran for about 30 seconds (on the fuel that I sucked down into the engine) then cut out.

I then removed the fuel line and left the vacuum line attached to both the bike and the fuel tank. Nothing flowed!

To conclude when sucking on the vacuum line fuel flows from the tank to the bike normally. But when the vacuum line is attached to the bike the fuel does not flow from the tank!

I replaced the vacuum line the other day for some new blue vacuum pipe as the old one was wore down badly. But its practically the same length as the old one.

The fuel and mileage gauges have also disappeared from the screen of the bike. But no engine warning light or anything like that.

Would really appreciate some advice on this as its currently costing £120+ per week in Uber rides to get to and from work without the bike.
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Nobby the Bastard
Harley Gaydar



Joined: 16 Aug 2013
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PostPosted: 17:50 - 21 Apr 2020    Post subject: Reply with quote
If you wanted a reliable 125 and need to rely on it why did you chose an Aprilla?
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trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050
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SilverFriends...
L Plate Warrior



Joined: 21 Apr 2020
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PostPosted: 17:53 - 21 Apr 2020    Post subject: Reply with quote
Nobby the Bastard wrote:
If you wanted a reliable 125 and need to rely on it why did you chose an Aprilla?


Because at the time I didn't need a reliable 125...

Lockdown forced me to come out of self employment into a warehouse operative role. Shit happens.

Not that this helps the current situation Rolling Eyes
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jaffa90
World Chat Champion



Joined: 06 Apr 2016
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PostPosted: 19:12 - 21 Apr 2020    Post subject: Reply with quote
Is the fuel tap serviceable as in pulling apart to get to the diaphragm?
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P.addy
Red Rocket



Joined: 14 Feb 2008
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PostPosted: 20:45 - 21 Apr 2020    Post subject: Re: Aprilia RS 125 fuel not flowing into engine! Reply with quote
SilverFriendship wrote:
The motorcycle has been sat for about 6 months without being started.


aaaaand its an RS125, mine shat itself after 8 months standing still. Would factor in a rebuild.
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1198
World Chat Champion



Joined: 24 Jan 2013
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PostPosted: 21:14 - 21 Apr 2020    Post subject: Reply with quote
Can you connect a fuel supply direct to the carb and bypass the vacuum tap? I find a Fairy bottle suffices very well!
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Riejufixing
World Chat Champion



Joined: 24 Jun 2018
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PostPosted: 21:17 - 21 Apr 2020    Post subject: Re: Aprilia RS 125 fuel not flowing into engine! Reply with quote
SilverFriendship wrote:
To conclude when sucking on the vacuum line fuel flows from the tank to the bike normally. But when the vacuum line is attached to the bike the fuel does not flow from the tank!

I replaced the vacuum line the other day for some new blue vacuum pipe as the old one was wore down badly. But its practically the same length as the old one.

The fuel and mileage gauges have also disappeared from the screen of the bike. But no engine warning light or anything like that.


So not sucking working? Why? The length of your new hose should not matter. Is the new hose kinking or collapsing when it's being sucked by the carb? Can you put the old one back on to check? Is the suction sucking when the thing runs for a minute after you've sucked it yourself?

It used to work.
It still works when you suck the hose yourself.
It doesn't work now.
The only think you've changed is the vacuum hose.
Perhaps the new hose leaks, or the engine sucks more than you do, and collapses the hose?
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SilverFriends...
L Plate Warrior



Joined: 21 Apr 2020
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PostPosted: 21:39 - 21 Apr 2020    Post subject: Reply with quote
1198 wrote:
Can you connect a fuel supply direct to the carb and bypass the vacuum tap? I find a Fairy bottle suffices very well!


So fill a fairy liquid bottle with some premixed petrol/oil and connect it directly to the fuel pipe that usually goes into the tank?

Sure I'll give this a try. Do I literally just hold the bottle upside down with the fuel in?

Just making sure I don't damage things more Smile

I imagine it will run fine under this setup. Because when i sucked a decent amount of fuel directly into the carb by sucking on the vacuum tube it ran great for 30 seconds. It was just clear that after that fuel burned off more fuel wasn't being sucked down the tube by the vacuum!
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Nobby the Bastard
Harley Gaydar



Joined: 16 Aug 2013
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PostPosted: 21:44 - 21 Apr 2020    Post subject: Reply with quote
Wouldn't it be easier to pull the fuel pipe off, stick it in a jar or bottle and suck the vacuum pipe and see if fuel comes out?
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050
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SilverFriends...
L Plate Warrior



Joined: 21 Apr 2020
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PostPosted: 21:47 - 21 Apr 2020    Post subject: Re: Aprilia RS 125 fuel not flowing into engine! Reply with quote
Riejufixing wrote:
SilverFriendship wrote:
To conclude when sucking on the vacuum line fuel flows from the tank to the bike normally. But when the vacuum line is attached to the bike the fuel does not flow from the tank!

I replaced the vacuum line the other day for some new blue vacuum pipe as the old one was wore down badly. But its practically the same length as the old one.

The fuel and mileage gauges have also disappeared from the screen of the bike. But no engine warning light or anything like that.


So not sucking working? Why? The length of your new hose should not matter. Is the new hose kinking or collapsing when it's being sucked by the carb? Can you put the old one back on to check? Is the suction sucking when the thing runs for a minute after you've sucked it yourself?

It used to work.
It still works when you suck the hose yourself.
It doesn't work now.
The only think you've changed is the vacuum hose.
Perhaps the new hose leaks, or the engine sucks more than you do, and collapses the hose?


Yes the petrol tap is working fine I think because fuel streams out when sucking on the vacuum line. The engine also turns over normally for 30-60 seconds when running on this fuel. It just doesn't get more fuel through the vacuum line once the fuel burns off that I manually sucked in.

Even when running for a good minute on the fuel that I sucked in it then cuts out. No more fuel makes it in from the vacuum line when its attached to the tank. So I think the vacuum definitely isn't working and I don't know why.

The tube I don't think is kinking with the suction from the carb as I elevated the tank slightly to observe the vacuum line while the engine was turning over from the manually sucked in fuel. It all appeared normal although I guess this can not be ruled entirely out. As it could be kinking near the carb that isn't visible to the eye.

I can't put the old vacuum line in place unfortunately as its cracked so much that its too short after trimming off the damaged ends.

The new vacuum line is sold as a replacement for Aprilia RS vacuum line and is very thick and rigid.

Thanks for the advice.
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SilverFriends...
L Plate Warrior



Joined: 21 Apr 2020
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PostPosted: 21:49 - 21 Apr 2020    Post subject: Reply with quote
Nobby the Bastard wrote:
Wouldn't it be easier to pull the fuel pipe off, stick it in a jar or bottle and suck the vacuum pipe and see if fuel comes out?


Already done that and the fuel comes normally out of the fuel pipe. The bike also turns over for 30-60 seconds on the fuel that I manually suck down when leaving the fuel line attached to the engine and sucking on the vacuum line.

Petrol comes out normally from the fuel pipe when sucking on the vacuum line.
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Riejufixing
World Chat Champion



Joined: 24 Jun 2018
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PostPosted: 21:53 - 21 Apr 2020    Post subject: Re: Aprilia RS 125 fuel not flowing into engine! Reply with quote
SilverFriendship wrote:
So I think the vacuum definitely isn't working and I don't know why

So what creates the vacuum? What happens if you get it running by sucking it yourself, then see if what's supposed to be sucking is actually sucking, e.g. by putting your finger over it to feel it?
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Nobby the Bastard
Harley Gaydar



Joined: 16 Aug 2013
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PostPosted: 22:03 - 21 Apr 2020    Post subject: Reply with quote
The vacuum is created by the carb/throttle body by air being sucked through it by a running engine so it's probably the connection between the carb/throttle body and the pipe.

Is there a prime position on the tap? This should bypass the vacuum.
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050
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bypass2
Spanner Monkey



Joined: 12 Sep 2013
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PostPosted: 22:13 - 21 Apr 2020    Post subject: Reply with quote
have you tried starting it with the petrol tap on prime then when it starts turn the tap to the on position. have you checked if the vent on the petrol cap is not blocked
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Riejufixing
World Chat Champion



Joined: 24 Jun 2018
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PostPosted: 22:46 - 21 Apr 2020    Post subject: Reply with quote
Nobby the Bastard wrote:
Is there a prime position on the tap? This should bypass the vacuum.

If he's lucky Smile I am not at all sure that these vacuum-operated petrol cocks are a good idea in general. I prefer the old "Turn the petrol on when you start, turn it off when you've finished" sort.
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jaffa90
World Chat Champion



Joined: 06 Apr 2016
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PostPosted: 23:27 - 21 Apr 2020    Post subject: Reply with quote
""""To conclude when sucking on the vacuum line fuel flows from the tank to the bike normally. But when the vacuum line is attached to the bike the fuel does not flow from the tank!"""

From what you say/state it sounds like a stiff diaphragm, more so when you get the engine running.

If the tap is not repairable then i would suggest removing it and soaking it in your wife`s nail polish remover or carb cleaner to soften the rubber diaphragm.
I have soften rubber diaphragms (with hard varnish) with cellulose thinners.
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Easy-X
Super Spammer



Joined: 08 Mar 2019
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PostPosted: 11:29 - 22 Apr 2020    Post subject: Reply with quote
Riejufixing wrote:
Nobby the Bastard wrote:
Is there a prime position on the tap? This should bypass the vacuum.

If he's lucky Smile I am not at all sure that these vacuum-operated petrol cocks are a good idea in general. I prefer the old "Turn the petrol on when you start, turn it off when you've finished" sort.


Vacuum valves... blame the lazy, "my life's just on automatic" scooter boys for popularising this useless tech Sad

1) Fuel container of some sort with a pipe from the bottom of the container. E.g. Upside down coke bottle, pipe jammed in and sealed with chewing gum... it doesn't have to be pretty, just a stand-in for a real tank: big container, pipe coming out the bottom Smile Does it run?

2) Assuming it does check your vacuum feed line again. Connect it back to the carb (or wherever it goes, probably close by) and get the engine running from the above test fuel supply. If you put your finger over the end of the pipe do you get sucked off? Laughing Laughing Laughing

I would guess you're either not getting vacuum or it's not sucking hard enough to get a reaction from the perished rubber* in the vacuum valve.

*free, bonus S&M reference
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Royal Enfield Continental GT 535, Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter
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