Slow Monster rebuild - Page 59

350TSS · 18-03-2019, 08:11 AM

The seat base mould now has 4 coats of 300g mat the divider has been drilled and bolted and and the complete mould is nearly ready for separation from the base plate. I am a bit worried that the seat contour might form a mechanical lock but we will give it a go tomorrow when the resin has fully cured
With both brain cells working overtime I think I now have a cunning plan for:
a) the formation of the ledge to locate the tank bottom mould and to provide a good sealing “gasket” face to bond to, and
b) the clear strip in the tank top mould acting as a fuel gauge (the idea has had a resurrection as I think I have a way of doing it which will not be adversely affected when I put the anti-ethanol resin in the tank after joining the top and bottom halves together).
Still exercising both cells is how to brace/baffle the inside of the tank. It dawned on me that if the tank holds 25 litres of fuel (ish) then that would be 25 kilos if it held water and about ¾ of that if it holds petrol - say up to 18 kilos. I would like to reinforce the internal structure around the mid mounting points on the bottom of the tank to spread the load but need to ensure that when I put the bottom of the tank in that the reinforcing structure actually is in contact with the top and the sides and is capable of being securely bonded in.
I picked up one of these on fleabay (from China) for the princely sum of £1.71 delivered.

I did not expect it to work but it does – it will fit in the petrol tank overflow pipe that will emerge from the little expansion hump in front of the filler cap

utopia · 18-03-2019, 12:48 PM

Is that a non-return breather valve ? ..... from China, and it actually works ?
That's a rare bird.
I've bought a couple of those from different sources recently and both of them did absolutely bugger all.

Mr Gazza · 18-03-2019, 05:24 PM

Am I missing something obvious here ? Or is it that a non-return valve is counter productive on a tank breather and pointless on an overflow?

The tank has to breathe out when sitting in the Sun or anywhere else warmer than where it has just been.. And in when the level goes down in use. It's a two way flow.

The valve must allow fuel outwards on an overflow, but what exactly is it preventing from returning if the hose is routed far enough downwards?

Sweet little valve though... There must be somewhere you can use it.

350TSS · 18-03-2019, 06:10 PM

My 750SS (carbie) has a Ducati one on the pipe leading from the little expansion hump at the front of the tank. I copied the hump for my tank and thought about buying a Ducati one for the M900 but lost interest when I saw the price, I never really questioned its function before but I do think you have a point Mr Gazza. I know similar devices are mandated on rally cars but that is to stop the petrol flooding out when the car lands on its roof. If I fit it I think I will still need a breather hole in the tank filler cap (or thereabouts ) otherwise I will get fuel starvation of the float bowls. Puzzling?????

Darkness · 18-03-2019, 06:55 PM

On the 750SS is the valve allowing air into the tank, but preventing escape of fuel when braking?

Mr Gazza · 18-03-2019, 06:58 PM

Yes, I had a very early 750SS myself, but never fully understood the "breather" hump.
I think mine had two hoses coming out of it, but it's a bit hazy now.

Out of interest, which way does the one way valve work on the SS hose?
If there are two hoses as I vaguely recall, then maybe they operate as one in and one out?

What's inside the hump? Any baffling or gauze strainer? Or just empty?

Edit.. This is interesting but doesn't really explain anything. https://c8software.com.au/shopv2/mor...0-ss/fuel-tank
You can hover over the part number and get a pop up identifying it.

Dennis menace · 19-03-2019, 09:58 AM

On my 750ss the valve is fitted as per the diagram and the flow is back to the tank but not away from it.

350TSS · 19-03-2019, 11:21 AM

Thanks Dennis Menace, so Darkness wins the technical query competition, although I am still puzzled as to how the tank "system" compensates for leaving the bike in the sun and the contents expanding (both air and fuel) with rising temperature????????????????

utopia · 19-03-2019, 12:44 PM

I have never really considered the need to relieve positive pressure from a hot tank.
I guess there could be some pressure increase on a very hot day, but this would be relieved as soon as you rode off and burnt a little fuel.

I've never owned an injection bike but I guess these would need a vent to relieve pressure from the pumped fuel return.
No such issues on a carby, where the main issue is relieving negative tank pressure as the fuel tries to flow out.

My own interest in the valve relates to the XT500 tank that I've fitted to my Dommie.
Here the filler cap is vented (breathes) via a spigot and rubber pipe which tucks down a hole in the steering stem nut.
My concern is to prevent fuel escaping out of this breather pipe if the bike falls over.

19-03-2019, 04:18 PM

This from the blurb from Newton Equipment on Tank Vent Valves. Mandatory in ACU race regs these days.

A Tank Vent Valve should allow air to enter the tank to replace the volume of fuel volume exiting the tank without allowing fuel to be lost through the vent system. In our design, should any fuel enter the valve, the hollow plastic ball will float on the fuel and seal the valve.

Mr Gazza · 19-03-2019, 04:37 PM

I had fuel erupting from my tank at last years Weekender, after filling up at the garage just up the road and then parking in the hot Sun back at the Hotel.
I filled normally as I always do, to the bottom of the rubber neck. So there was air space before I correctly closed the filler cap, I then rode the mile or whatever it was back down the hill. Thinking about it the engine would have still been hot from the run too.

I have to assume that my drain is blocked in the filler cavity, or that it was over awed. But either way it demonstrated that fuel expansion is a real and vivid phenomenon.

I imagine the valve on the SS is a ball valve as Raven describes, but would still have an arrow indicating direction of fitment even though it may not be a full on non-return valve in the normal sense?

utopia · 19-03-2019, 06:41 PM

I have no personal experience of injection bikes, but here's a train of thought ....
Assuming that the electric fuel pump runs at a constant speed, ie it delivers a constant volume flow rate irrespective of engine revs, then a slow trundle back from the garage at relatively low revs would use little fuel and result in a high rate of fuel return to the tank.
If there is a one way "air in" vent (breather) and if there is also a pressure relief vent which is malfunctioning, then pressure would build up in the tank irrespective of any heating effects .. would it not ?

I think Capo posted a little feature on how the fuel cap vents work (on his injection, S4R), but that was some years ago .. and the pics are probably lost down the photobucket hole.
I'd bet he still has the info on file though.

Sorry for the hijack .... though we've been pretty good so far on such an (excellent) extended thread.

Mr Gazza · 19-03-2019, 06:59 PM

I'm a bit surprised at your thoughts about a higher rate of return.
The volume of fuel can only go down once the cap is closed.(assuming a constant temperature.) There's nowhere for any extra fuel to come from.

The tank, along with the pump and fuel rail are full of fuel.
The pump pressurises the fuel rail (a very low positive pressure), and pumps fuel round it, back into the tank. Fuel exits via the injectors at a variable rate, but there is always an over supply and fuel constantly returns to the tank whether needed or not.

In order to return more than it has taken from the tank in the first place, it would have to draw from some other supply.... It's a loop. It just sucks in one end and squirts out the other with a bit lost in the middle on demand.

I have Capo's article on fuel caps, with pictures. But I have tried without success to post it before.. Sorry.

Darkness · 19-03-2019, 07:17 PM

Quote:

Originally Posted by Mr Gazza

I'm a bit surprised at your thoughts about a higher rate of return.
The volume of fuel can only go down once the cap is closed.(assuming a constant temperature.) There's nowhere for any extra fuel to come from.

The tank, along with the pump and fuel rail are full of fuel.
The pump pressurises the fuel rail (a very low positive pressure), and pumps fuel round it, back into the tank. Fuel exits via the injectors at a variable rate, but there is always an over supply and fuel constantly returns to the tank whether needed or not.

In order to return more than it has taken from the tank in the first place, it would have to draw from some other supply.... It's a loop. It just sucks in one end and squirts out the other with a bit lost in the middle on demand.

I have Capo's article on fuel caps, with pictures. But I have tried without success to post it before.. Sorry.

Yes, that’s my take on it too.

The only reason for petrol to come try to get out of the tank through the breather are if it’s got seriously hot since the tank cap was filled, or you are standing the bike on its front wheel braking, so all of the fuel rushes to the front of the tank.

utopia · 20-03-2019, 01:14 AM

Yes, it was a bit of a half-hearted pondering, tbh.
My feeble excuse is that I was concentrating on valve clearance adjustment at the time.

I'll get my coat.

18-03-2019, 05:24 PM	#3
Mr Gazza Lord of the Rings Join Date: May 2013 Location: Norwich Bike: M900sie Posts: 5,834	Am I missing something obvious here ? Or is it that a non-return valve is counter productive on a tank breather and pointless on an overflow? The tank has to breathe out when sitting in the Sun or anywhere else warmer than where it has just been.. And in when the level goes down in use. It's a two way flow. The valve must allow fuel outwards on an overflow, but what exactly is it preventing from returning if the hose is routed far enough downwards? Sweet little valve though... There must be somewhere you can use it. __________________

18-03-2019, 06:55 PM	#5
Darkness . Join Date: May 2007 Location: Stockbridge Bike: M900 Posts: 1,984	On the 750SS is the valve allowing air into the tank, but preventing escape of fuel when braking? __________________ Original and Best since 1993

18-03-2019, 06:58 PM	#6
Mr Gazza Lord of the Rings Join Date: May 2013 Location: Norwich Bike: M900sie Posts: 5,834	Yes, I had a very early 750SS myself, but never fully understood the "breather" hump. I think mine had two hoses coming out of it, but it's a bit hazy now. Out of interest, which way does the one way valve work on the SS hose? If there are two hoses as I vaguely recall, then maybe they operate as one in and one out? What's inside the hump? Any baffling or gauze strainer? Or just empty? Edit.. This is interesting but doesn't really explain anything. https://c8software.com.au/shopv2/mor...0-ss/fuel-tank You can hover over the part number and get a pop up identifying it. __________________ Last edited by Mr Gazza; 18-03-2019 at 07:16 PM..

19-03-2019, 04:37 PM	#11
Mr Gazza Lord of the Rings Join Date: May 2013 Location: Norwich Bike: M900sie Posts: 5,834	I had fuel erupting from my tank at last years Weekender, after filling up at the garage just up the road and then parking in the hot Sun back at the Hotel. I filled normally as I always do, to the bottom of the rubber neck. So there was air space before I correctly closed the filler cap, I then rode the mile or whatever it was back down the hill. Thinking about it the engine would have still been hot from the run too. I have to assume that my drain is blocked in the filler cavity, or that it was over awed. But either way it demonstrated that fuel expansion is a real and vivid phenomenon. I imagine the valve on the SS is a ball valve as Raven describes, but would still have an arrow indicating direction of fitment even though it may not be a full on non-return valve in the normal sense? __________________

19-03-2019, 06:59 PM	#13
Mr Gazza Lord of the Rings Join Date: May 2013 Location: Norwich Bike: M900sie Posts: 5,834	I'm a bit surprised at your thoughts about a higher rate of return. The volume of fuel can only go down once the cap is closed.(assuming a constant temperature.) There's nowhere for any extra fuel to come from. The tank, along with the pump and fuel rail are full of fuel. The pump pressurises the fuel rail (a very low positive pressure), and pumps fuel round it, back into the tank. Fuel exits via the injectors at a variable rate, but there is always an over supply and fuel constantly returns to the tank whether needed or not. In order to return more than it has taken from the tank in the first place, it would have to draw from some other supply.... It's a loop. It just sucks in one end and squirts out the other with a bit lost in the middle on demand. I have Capo's article on fuel caps, with pictures. But I have tried without success to post it before.. Sorry. __________________

18-03-2019, 08:11 AM	#1
350TSS Too much time on my hands member Join Date: Jan 2013 Location: Shipbourne Bike: M900 Posts: 1,419	The seat base mould now has 4 coats of 300g mat the divider has been drilled and bolted and and the complete mould is nearly ready for separation from the base plate. I am a bit worried that the seat contour might form a mechanical lock but we will give it a go tomorrow when the resin has fully cured With both brain cells working overtime I think I now have a cunning plan for: a) the formation of the ledge to locate the tank bottom mould and to provide a good sealing “gasket” face to bond to, and b) the clear strip in the tank top mould acting as a fuel gauge (the idea has had a resurrection as I think I have a way of doing it which will not be adversely affected when I put the anti-ethanol resin in the tank after joining the top and bottom halves together). Still exercising both cells is how to brace/baffle the inside of the tank. It dawned on me that if the tank holds 25 litres of fuel (ish) then that would be 25 kilos if it held water and about ¾ of that if it holds petrol - say up to 18 kilos. I would like to reinforce the internal structure around the mid mounting points on the bottom of the tank to spread the load but need to ensure that when I put the bottom of the tank in that the reinforcing structure actually is in contact with the top and the sides and is capable of being securely bonded in. I picked up one of these on fleabay (from China) for the princely sum of £1.71 delivered. I did not expect it to work but it does – it will fit in the petrol tank overflow pipe that will emerge from the little expansion hump in front of the filler cap

18-03-2019, 12:48 PM	#2
utopia No turn left unstoned Join Date: Jun 2010 Location: leicester Bike: M750 Posts: 4,545	Is that a non-return breather valve ? ..... from China, and it actually works ? That's a rare bird. I've bought a couple of those from different sources recently and both of them did absolutely bugger all.

18-03-2019, 06:10 PM	#4
350TSS Too much time on my hands member Join Date: Jan 2013 Location: Shipbourne Bike: M900 Posts: 1,419	My 750SS (carbie) has a Ducati one on the pipe leading from the little expansion hump at the front of the tank. I copied the hump for my tank and thought about buying a Ducati one for the M900 but lost interest when I saw the price, I never really questioned its function before but I do think you have a point Mr Gazza. I know similar devices are mandated on rally cars but that is to stop the petrol flooding out when the car lands on its roof. If I fit it I think I will still need a breather hole in the tank filler cap (or thereabouts ) otherwise I will get fuel starvation of the float bowls. Puzzling?????

19-03-2019, 09:58 AM	#7
Dennis menace Registered User Join Date: Nov 2013 Location: Farnsfield Bike: Other Ducati Posts: 300	On my 750ss the valve is fitted as per the diagram and the flow is back to the tank but not away from it.

19-03-2019, 11:21 AM	#8
350TSS Too much time on my hands member Join Date: Jan 2013 Location: Shipbourne Bike: M900 Posts: 1,419	Thanks Dennis Menace, so Darkness wins the technical query competition, although I am still puzzled as to how the tank "system" compensates for leaving the bike in the sun and the contents expanding (both air and fuel) with rising temperature????????????????

19-03-2019, 12:44 PM	#9
utopia No turn left unstoned Join Date: Jun 2010 Location: leicester Bike: M750 Posts: 4,545	I have never really considered the need to relieve positive pressure from a hot tank. I guess there could be some pressure increase on a very hot day, but this would be relieved as soon as you rode off and burnt a little fuel. I've never owned an injection bike but I guess these would need a vent to relieve pressure from the pumped fuel return. No such issues on a carby, where the main issue is relieving negative tank pressure as the fuel tries to flow out. My own interest in the valve relates to the XT500 tank that I've fitted to my Dommie. Here the filler cap is vented (breathes) via a spigot and rubber pipe which tucks down a hole in the steering stem nut. My concern is to prevent fuel escaping out of this breather pipe if the bike falls over.

19-03-2019, 04:18 PM	#10
Raven Guest Posts: n/a	This from the blurb from Newton Equipment on Tank Vent Valves. Mandatory in ACU race regs these days. A Tank Vent Valve should allow air to enter the tank to replace the volume of fuel volume exiting the tank without allowing fuel to be lost through the vent system. In our design, should any fuel enter the valve, the hollow plastic ball will float on the fuel and seal the valve.

19-03-2019, 06:41 PM	#12
utopia No turn left unstoned Join Date: Jun 2010 Location: leicester Bike: M750 Posts: 4,545	I have no personal experience of injection bikes, but here's a train of thought .... Assuming that the electric fuel pump runs at a constant speed, ie it delivers a constant volume flow rate irrespective of engine revs, then a slow trundle back from the garage at relatively low revs would use little fuel and result in a high rate of fuel return to the tank. If there is a one way "air in" vent (breather) and if there is also a pressure relief vent which is malfunctioning, then pressure would build up in the tank irrespective of any heating effects .. would it not ? I think Capo posted a little feature on how the fuel cap vents work (on his injection, S4R), but that was some years ago .. and the pics are probably lost down the photobucket hole. I'd bet he still has the info on file though. Sorry for the hijack .... though we've been pretty good so far on such an (excellent) extended thread.

20-03-2019, 01:14 AM	#15
utopia No turn left unstoned Join Date: Jun 2010 Location: leicester Bike: M750 Posts: 4,545	Yes, it was a bit of a half-hearted pondering, tbh. My feeble excuse is that I was concentrating on valve clearance adjustment at the time. I'll get my coat.