Suzuki Srad Fuel Tank Pump Flange Modifications

A typical fault with the Suzuki SRAD tank was the pump seal arrangement on the bottom of the tank.

If the pump and flange plate were removed for any reason and then refitted, there was a big chance that with a fraction excessive tightening of the clamp bolts that the spot welded flange would distort and then the sandwiched seal ring would not pull tight against the flared opening flange of the tank.

Major problem if you had done the above, filled the tank and had fuel pouring out the bottom of the tank on a nice hot engine / gearbox casing. Very poor design by Suzuki really.

Anyway, my customer having spent a good wedge of cash on getting his tank repainted was left in the same position the first time he put new fuel in his nice newly painted tank. Upon inspection it could be seen that the flange the clamp bolts thread into had distorted and hence the seal ring was not sealing against the tank flange lip.

As can be seen from the image above the original set up takes the form of a 4mm thick flange that is spot welded to the main tank in between the threaded bolt positions, you may also be able to see the dimples in the tank under the positions where the clamping bolts sit through the flange so the bolts dont actually damage the tank shell. You can also see the pressed up flange around the opening that the seal ring actually seals against when the whole thing is tightened up. Clearly also shown are the positions where the spot welds have been positioned in between the drilled and tapped holes.

Above image shows where I have had to drill out the spot welds in the original flange in order to get the damn thing off – best spot welds I have ever removed! This took a bit of tugging and hammering to get off and the next image shows that I then had to do a little panel beating with a small aluminium block to level the panel work back up a bit.

A little bit of flushing off and a bit of sanding down and cleaning up and we are ready to fit the new flange.

Laser cut, mild steel, thicker 6mm pump mounting flange offered up in place on the original tank. This will be tacked and welded in place using a 10mm thick top plate to help soak some heat away and to help stop the new flange from distorting whilst welding.

1st we need to drill and tap out the holes. Drill out 5mm (4.8mm actually) diameter in order to tap M6. I did this using a battery drill set at low torque setting to prevent breaking the tap off in the hole. Notice that I didnt get the holes laser cut as this leaves a “hard” surface on the material which is a nightmare to thread out then, so all I did was get the laser to put a cross mark exactly where the holes come, ensuring dead accurate marking.

Once all the holes were drilled and tapped out, a double check on the orientation and bolt the blanking flange up, sett up on the tank for accurate tack up.

Once tacked up, I removed the blanking plate and double checked the tack up and positioning. I had to make sure that I clamped the tank panel work tight up to the flange. Unfortunately even with the new flange tacked tight up I still had a gap to fill where the original dimples in the tank are, so I had to weld as cool as possible but a large fillet size to cover the dimples.

Once the weld had had time to cool down I removed the blanking plate, although the flange had stayed flat and level there was a bit of shrinkage in the panel work.

The blanking plate was the used as a template to make a silicon rubber seal for testing, I also had to drill the blank plate and weld 2 pipe stubs on so that I could connect an airline and pressure blow off valve.

The seal and clamping plate were bolted back in place and tightened up I connected an airline one side and a pressure relief blow off valve the other. Spraying soapy water around the welded area and then pressuring up the tank if there is a leak you can see air bubbles bubbling out of pinholes etc.

On to dry off, clean up, bit of paint and jobs a good un!

Just waiting for the laser cut nitrile seal to clamp up and finish the job.

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Ducati Oil Catch Tank

A nice little fabricated aluminium oil catch tank to fit up behind the head stock and between frame spars on a customers special build Ducati motorcycle.

Initially a simple card mock up was made and changed several times just to get the tank to sit tight up and at the right angle to the frame miss all parts required.

Once the mock up was complete and we was happy with it, I cut out and pressed up the tank in 2 sections of 1.5mm ns4 aluminium.

Just to make sure I tacked the tank up and we tried it in position to ensure it wasnt going to catch anything as it is maneuvered into place. Once held in position we could see what actual room we had available to us and where we could put breather, site glass, filler cap (to empty in this case), and of course the mounting points. Very little room was left and we decided to mount the tank on welded brackets to each side frame spar, this also then needed thought to be able to bolt the tank in position. The best idea we came up with was to machine top hat, blind threaded bosses to weld into the bottom of the tank. Shown below.

Now the mounting top hats are welded in we can see that there is very little room for the breather and inlet pipe, made from 6mm aluminium tube with a 1mm wall thickness.

So above you can see that the bottom of the tank is quite “busy”, the pipes had to be welded into the bottom of the tank as there was no room above or down the sides of the tank to run flexible hoses.

So if we look at the other fittings on the tank you can see the black filler bung is on the top, the sight gauge is mounted half way down the tank (black with clear lens) and if the oil mist ever fills enough you will see oil in the tank.

Both of these fittings had a simple little machined threaded boss with a “flange” round the top. My customer actually provided the machined fittings, only the filler threaded fitting had very little top flange to weld to. This with aluminium can be a problem as unless we have a flange with a little “meat” on it will rapidly be saturated in heat and “blow” away before we fuse to the main tank.

Aluminium dissipates heat very quickly unlike stainless steel or mild steel, but as this tank was so small and thin it quickly became “heat saturated” and you really have to watch the heat input otherwise the weld will “flood out” and look poor as well as being uneven and have massive excess penetration into the tank.

Above you can see how small the flange was on the filler boss, only approx 2mm in section.

So once complete and welded up the tank needed to be tested for leaks, a simple process whereby we block all the holes up, add air pressure into the tank and simply brush soapy water around all the joints and welds. If there are any pin holes then the air will bubble through. Luckily this had no such issue.

Above you can see the finished article and the basic drawing we worked to.

Now the tank is complete my customer is taking the whole bike to Italy to a specialist frame builder to have a frame built.

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