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Old 20-12-2018, 08:27 PM   #841
350TSS
Too much time on my hands member
 
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Join Date: Jan 2013
Location: Shipbourne
Bike: M900
Posts: 1,417
Today I have mostly been making ……………………………..swarf.
The fuel filler neck to be slightly more accurate from a 60mm long billet of 2.5” round bar to a c4mm wall tube with an ID of variously 45mm and 43mm. The fuel filler neck will be bonded permanently into the tank filler recess.

I made it a bit more complicated by deciding to make provision for a re-moveable mesh stainless steel filter. I found a supplier of the mesh on fleabay who offered various grades as follows:
Mesh Count Description Nominal
Aperture (mm) Wire Diameter Open Area (%) Weight kg/m²
4 Heavy 5.45 0.9mm (20 SWG) 74 1.61
8 Varroa 2.47 0.71mm (22 SWG) 60 2.00
10 Coarse 1.98 0.56mm (24 SWG) 61 1.51
20 Medium 0.915 355µm (28 SWG) 52 1.25
30 Insect Screen 0.567 280µm (32 SWG) 45 1.17
40 Vivarium Vent 0.411 224µm (34 SWG) 42 1.00
60 Papermaking 0.263 160µm (37 SWG) 39 0.76
80 Fine 0.178 140µm (39 SWG) 31 0.78
120 Filter 0.122 90µm (43 SWG) 33 0.48
200 Super Fine 0.075 53µm (47 SWG) 34 0.28
400 Metal Silk 0.035 28µm (49 SWG) 31 0.16

I opted for the 40 grade being a compromise between stopping rubbish (but not water) getting into the tank and not choking the filling process too much so that the petrol delivery pump does not sense the back pressure and auto stop. With only a 42% open area of the mesh the effective size of the hole at the bottom will have to be c2.4 times the surface area of the internal diameter of the neck. The neck can only be 60mm deep because on the original tank the space between the filler recess and the bottom of the tank is that big, the original air box is a massive intrusion into the tank capacity. My tank design is deeper but I have no way currently of measuring by how much so I decided to opt for the original Monster tank dimension. The limited original depth of the filler neck obviously restricts your ability to meet that ratio.
Thinking about it as I write I could probably have got away with the 60 grade mesh, however the mesh was only £2.99 for a 150mm x 150mm sheet so I could easily buy the finer mesh when I have some experience of the tank filling without auto stopping the petrol delivery pump.
The design I have come up with I think nearly makes that 2.4 ratio but still allows the mesh filter to be attached to the neck and be capable of removal for cleaning.
Water ingress is by far the most likely contaminator of the fuel and this will be alleviated by using a British bike style fuel tap (with reserve tap and with right angle exit hole also with mesh filter on the dual entry ports) threaded into an aluminium boss which will be bonded into the tank. This boss will have a “ditch” to trap any remaining water. Finally the original plastic circular filter will sit between the tank and the vacuum pump.
The tank will be vented via a boss on the blister on the top of the tank connected to non-return valve as per a 900SS. The original Monster tank also I think has a vent in the filler recess connected via internal pipework to a drain pipe that exits from the tank near the petrol outlet pipe and is connected to a drain tube and thence to atmosphere/road. I am reluctant to include this complication as it is another potential place where leaks can occur but you may convince me otherwise.
I did a check on the rear sprocket stud/swinging arm potential clash and I think the picture taken from directly above shows that there will be clearance, not much but a few mm as the spindle boss which is/will be bearing on the swinging arm clearly protrudes further than the sprocket studs. Chain alignment will obviously be checked on assembly.

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