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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Alloy welding / repairs, custom parts, Welding Instruction.

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Threading and Tapping Holes in Metal

A tap

standard 3 piece tap set

cuts threads on the inside of a hole – known as FEMALE threads, to accept a machine screw or bolt. Taps can also be used to restore an internal thread

Typical Internal Thread

that has been damaged or to cut a new, larger thread in the case of severe damage or stripping.

The opposite of an internal thread is an external thread – MALE thread

External Thread

which you can cut using a die

Split Die

Taps come in 3 types – usually as a “set”, starting a first cut, middle or 2nd cut and lastly a bottoming or plug tap. 1st cut has the most taper and is design to start the thread in a new hole, 2nd has a bit less, bottoming will cut threads all the way to the bottom of a blind hole. You can usually get away with just 2nd and bottoming. If you are cleaning out a hole, I would use 2nd or plug tap because there is less risk of cross threading, which is easy to do in a mangled thread.

Dies on the other hand usually come as a Split Die – this is to allow the Die to be “opened out” to make the first cut on a round shaft easier to start (similar to a first cut tap), and then closed a little to finish the thread to a good fit to the nut or female thread.

So to recap a “TAP” is used to make a FEMALE or INTERNAL THREAD, a “DIE” is used to make a MALE or EXTERNAL THREAD.

A TAP needs a TAP HANDLE which clamps the “tap” in place in order to be able to manually turn the tap to produce the cutting action

Tap Handle

These come in various forms, as above or

Tap Wrench

Both types are often called a “TAP WRENCH”

If we are going to put a female thread into a part we will need to know what size to drill the hole. In order to do this we must look this up on a “Tapping drill” chart see example below.

Tapping Drill Size table

A good idea for most engineers is to invest a couple of pounds into a ZEUS book which contains many “technical” charts / tables / formula that engineers require – they are worth every penny –

An extremely handy pocket sized reference booklet of data charts and tables for the drawing office, toolroom or workshop.

This metric revision publication is produced by Zeus Precision Charts Ltd, who are members of the British Standards Institution.

The 28 laminated pages contain data on standard drill sizes and decimal equivalents, tapping drills and clearances for metric and imperial threads, BS4500 tolerances, hardness comparisons, jig boring co-ordinates for equally spaced holes, allowances for sheet metal bending and Morse tapers.

Also, long tables for sine, cosine, tangents and cotangent.

Threading a hole is a skill, the tap has to be aligned with the hole and care needs to be taken to ensure that the thread stays aligned with the drilled hole otherwise you can end up with a thread running at an angle to the hole that has been drilled.

When tapping a standard right handed thread you must take great care to “break off” the swarf that is being cut from the inside wall of the hole. To do this we wind the tap in clockwise 1 turn at a time, stop and then turn back (anti-clockwise) 1/2 a turn. It is also a good idea to use some form of cutting compound to “ease” the process.

Typical Manual Tapping

Great care must also be taken with consideration to force being used and resistance being felt through the tap handle. If there is excess swarf build up the the rotary motion of turning the tap becomes difficult and “tight”, this may also be true if no tapping / cutting fluid or compound is used and certainly if the hole has been drilled out too small. As the actual tap is made of hardened steel it is possible to break a Tap off in the hole you are tapping, particularly with smaller taps.

Automated tapping heads are available for pedestal drilling machines, these actually reverse the action before too much pressure is built up thus reducing the chance of breaking a tap.

More than likely though it is worth investing in a good quality Tap & Die set – Recommended is this DRAPER set – if looked after will last a life time.

Draper 79203 37-Piece Tap and Die Set

Click on image to take you to Amazon site

Product Description

Manufactured from carbon steel. Taps and dies suitable for cleaning and cutting threads on mild steel and aluminium. Supplied with the correct drill bits for tapping. Contents held in plastic insert within steel storage case.

We can repair threads in aluminium, mild steel, stainless steel & castings

SEE –

www.flashcustoms.co.uk

Don`t forget to email or call us for all your custom made 1 off bespoke items.

Thanks for reading our blog – we hope this has been of use to you.

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FLASH CUSTOMS – Specialist Custom Car & Motorcycle Parts

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