Buell Motorcycle Swing Arm Modifications

Buell Motorcycle Swing Arm Modifications.

Wicked change over and modification this job.

My customer has asked me to modify and extend a cast aluminium swing arm to give him a wider rear wheel section.

Here is the Non standard swing arm to modify.


Now the Buell motorcycle that this aluminium swing arm is to mate up to has a simple steel swing arm affair (the difference shown below). And there are also pictures showing the aluminium swing arm offered up to the original steel frame and back end gearbox pivot mounting. Note that we are extending the swing arm by 100mm to ensure the next size belt drive fits and extend the wheelbase marginally which helps reduce front end lifting so easily under accelleration.


If you have ever considered a similar modification for your motorcycle you will know that there are many things to consider.

Points to consider

  1. Mountings
  2. Bearings
  3. Swing angle
  4. Coil over / linkages if used?
  5. Offsets of wheel
  6. Offset of Mounting in Frame
  7. Offset of drive sprocket to wheel centre and frame centre
  8. Relocation of pipework, cables
  9. Chain or belt clearance
  10. Revised mountings for chain guard, rear sets, exhaust, rear brake
  11. Any areas of interference e.g. is the assembly going to hit any part upon compression of suspension.
  12. Maintaining rear / front wheel alignment / centres
  13. Accurate and equal measurements between wheel centre and new pivot point centres,otherwise rear wheel will be out of alignment.
  14. Strength, rigidity, flexibility
  15. Welding and machining skills, design and manufacture skills
  16. and so on !

So all in all not a job for the feint hearted. As you can see there are many things that need consideration before any work takes place.


How did I complete this job?

A complete breakdown of this modification can be seen below.

Measure, measure and check again! 

I use any number of methods to work out all the above. First and foremost an image in my head of how I think I can tackle the job, what the end result may look like, will I be able to make it “work”. Its no surprise what people throw at me as far doing custom made jobs. Often upon initial conversation / email I may not know if I can make / modify / fit / manufacture what the customer requires. Often its a case of getting more information / pictures / sketches / notes / dimensions etc to fathom out if indeed it is even possible and will work.

Once I have pictured the overall job and agreed that I can do it, there may be several steps involved in being sure I can make what the customer wants as I may have a different picture in my head to what the customer thinks.

Anyway this modification was quite logical in planning and implementing.

A marked out layout was completed on my work bench using the wheel centre as a datum point. I then overlayed the original and also the new swing arms. Instantly this gives me a layout that I can pattern from. By doing this I can compare what dimensions I have to work from to make the new swing arm fit to the back end mounting in the frame for the original pivot point. At this stage a flat template was made from aluminium as a check and compare guide.

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Once the template had been made and offered up to the frame and original pivot mounting points I could clearly see that the pivot mounting point and frame centre line was some 10mm out of alignment. This meant that the template and layout had to be adjusted to ensure that the centre line of the rear wheel was moved over to correct the offset and ensure the frame and rear wheel centre line is on the same plane.

Designing the new Swing Arm Extension

Once the correct layout, centre lines and overall plan is checked and double checked again, I know what we have to work with. At this point I have designed a 3d model of the infill piece which will extend  the swing arm by 100mm. The item will be machined from one block of material and be pinned and welded to the aluminium swing arm.

This positive positioning will be via 2 aluminium “top hat” pins that will be a press fit into the adapter / extension piece and also the bearing bore on  the actual aluminium swing arm. Once happy with the fit these will be welded in position and the slab side of the extension will also be fully welded all round to the swing arm. Creating a fully fitted extremely strong extension piece which is now one part with the swing arm.

Initially several sketches were made to clear my mind dimension were correct and also to put my ideas on paper to be able to produce a model. Careful thought needed putting in to design of the item to meet all the parameters and miss vital components such as the back edge of the main framework.

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Sketches always help me with considering a design for a one off job and clarifies points in my head and what I want it to look like. From the sketches I can easily make a 3d model as below
swing arm mods (2)

The above image shows a 1 piece extension unit complete with front pivot bearings and rear top hat pins in place. From this an engineering drawing was produced to enable manufacture. This included all dimension required to ensure dimensions and fits for bearings and pins are all to tolerance and “work” accordingly as designed.

swing arm dwgpin bosses dwg

Points to consider when designing this part !

Strength, weight, size, machine-ability, weld-ability, fit, finish, conflict with other parts (as its a moving part).

So all above considered this was the final machined extension piece manufactured from T6 Aluminium.

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Once checked dimensionaly and any sharp edges removed the next step was to offer up to the cleaned up swing arm, removing all the original paint to ensure no weld contamination in the welded areas we could tack up and check against the frame before final welding.

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2 images above show the main extension welded to the original swing arm. Location was critical and so top hat pins were machined up to a light push fit into the new extension and aligning with the original bearing bores in the swing arm. This ensures a “true” aligned extension piece. Once all tacked and aligned the whole unit was fully welded using the TIG welding process. As the swing arm incorporated an oil tank within the pivot end of the swing arm, some difficulties occurred in welding as due to the nature of alloy being porous oil soaks into the material somewhat. This is fine but during the welding process this contamination “burns out” and floats on top of the weld pool.

Once welded the surface of the weld was cleaned with a skotch pad to remove any surface contamination. Weld integrity is critical on a job like this where so many forces are travelling through and acting on the pivot point. In this instance there is in excess of 600mm of weld all around the added extension piece to original swing arm so its not going anywhere.

Infill panels were then cut, positioned and welded in position to finish the “boxing in” of the extension piece.

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To add more strength and infill the area above the new extension I added a fabricated triangulated section which ties in the extension fully to the original swing arm – see image below.

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Final shots of the new swing arm fitted up to the frame – below

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Thanks for looking, hope this blog was useful to you and remember if I can help you with your project please don’t hesitate to give me a call, or use the contact form above.









Ducati Laser Cut and Etched Mirror, Ideal Gift

We can take any image and produce a file from it to cut and etch in detail on a sheet of mirror stainless steel thus producing an individual Mirror.

Ideal as a gift or present for a loved one, size and dimension are only limited by sheet size typically up to 2m x 1m

Alternatively if you require an individually crafted kitchen or bathroom splash back we can offer this as well – either with an etched design or a shaped panel – e.g. Love heart, Kettle, Apple, let your imagination run wild.

Ducati Mirror

Ducati Mirror

I have a couple of these spare if anyone is interested @ £40 plus £7 p&p please message me or call me on 07866911093

Also – Stainless steel Splash backs, door kick / bash panels / stainless tabletops / work surfaces also supplied to order.

We look forward to keeping you up to date.

For all your Custom Car & Motorcycle Parts, Manufacture and Welding / Repairs

Alloy welding / repairs, custom parts, Welding Instruction.


Seat Aftermarket Intercooler Repair

Alloy Intercooler Repair

This is what happens when you mount an oversize intercooler, and then drop the car on the floor as low as possible; speed humps and rough local roads all add to the damage.

Many things can affect the performance of your car – a holed, leaking intercooler can play havoc with boost levels and drastically reduce overall power. So not an ideal scenario. The key to modifying cars (and bikes) is if you are going to, is to make the changes safely and well engineered. If this intercooler had managed to pick up dust and or stones when scrapping the tarmac this could have led to a catastrophic failure of the engine. Luckily this wasn’t the case this time.

Looking at the above Intercooler repair you can see that the bottom corners had been worn through and needed cleaning and repairing, I used the alloy chequer plate corner patch plates to give a bit more thickness and strength to the bottom corners.

My customer used the slots in the mounting brackets to lift the intercooler about 10mm higher to try and reduce the chance of further damage. My advice was if there was still a problem with it bottoming out in future, modifications to the end cans could be made to shorten the overall height by some 20mm, this would have been ideal but would have taken a little more work.

We look forward to keeping you up to date.

For all your Custom Car & Motorcycle Parts, Manufacture and Welding / Repairs

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

Alloy welding / repairs, custom parts, Welding Instruction.

Throttle Body Intake Plenum for Cambridge University Students Project

I had been approached by a student in his final year at Cambridge University. He had modeled up exactly what was required, I had all the drawings and even flat layout patterns for the cones and wraps. So a bit spoilt on this one really but, apparently no one else would take this on in 1mm aluminium. I relished the challenge.

Duly parts were laser cut where possible and I started some real sheet metal work shaping with rolls, planishing hammers and stakes to form up the panel work to suit.

A lot of work went into this as all the joints had to match up spot on as I was going to need to purge the welds to leave a nice smooth bead of penetration on the inside.

As the material was only 1mm thick heat input was difficult to control as with aluminium heat is sucked away from the weld pool area. However, with the material being so thin once a weld pool was formed if I didn`t feed filler wire in immediately them it would drop through and leave a hole in the joint. Careful control with a foot pedal was needed to keep the welded joint from “blowing away”.


Fabrication of the main plenum had been analysed by the final year students to allow good airflow in conjunction with the rules and regulations under which they was going to be racing this single seater car. All parts had to be fabricated and welded together by the TIG welding process, other parts included cnc machined bell mouths and laser cut panels and flange. I also had to machine up a couple of bosses to incorporate sensors into the plenum.

The most difficult thing about this job was the simple fact that the drawings allowed little or no material from the bell mouths to the edge of the back plate, When welding such thick cnc machined parts to such thin sheet material the difficulty is always getting enough heat in the thicker part without melting away the thinner part. This was accomplished in a couple of ways. Firstly the back plate was sat on an aluminium heat sink block which helped drag some of the heat away from the thin material whilst directing the arc at the thicker bell mouth part. In future it would be advisable to leave a “land” if possible in order to reduce the chance of blowing away the thin sheet before sufficient heat build up was gained in the machined bell mouths.

Purging the inside of the plenum during welding with argon reduces the chance of atmospheric attack on the inside as weld penetration comes through the joint. This also helps in maintaining a nice smooth bead around the inside which will not disturb the airflow as much as if we hadn’t purged the joints. If I didn’t bother purging when welding the inside penetration bead would have been rough and inconsistent and possibly even hang through like “grapes” as we in the know call it. This would have been unacceptable for the job in hand.


We look forward to keeping you up to date.

For all your Custom Car & Motorcycle Parts, Manufacture and Welding / Repairs
Don`t forget to email or call us for all your custom made 1 off bespoke items.

Alloy welding / repairs, custom parts, Welding Instruction.

Brake and Clutch Fluid Tank, Polished Stainless

Brake and Clutch Fluid Tank, Polished Stainless

I started this small project with a letter and some fittings from my customer. He had seen my previous work on our website www.flashcustoms.co.uk and wanted an integrated fluid tank for brake system and hydraulic clutch system. It was to be bulkhead mounted with 3 off 4an fittings, lower to be brake system, upper to be clutch system.

It had to be mirror stainless steel as it was being fitted to a top end Dax Cobra Replica.

I pride myself on completing 1 off custom made parts such as this and to ensure that everything is millimeter perfect I used solid works 3 d  modeling package to draw up the item and produce a dxf (drawing exchange file) to send to our laser cutting system.

The material itself is 304 BA (bright annealed) stainless steel in 1.5mm thick. Bright annealed is a chemical etch finish on the surface of the stainless which is almost like a dull polish. This eliminates some of the time involved in bringing the parts up to a “mirror” finish prior to assembly and welding.

Please see below photos of parts and assembly process

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Tomorrow I will Post up pictures and details of the finishing processes I use to ensure the whole tank is mirror polished and pressure tested for leaks.

We look forward to keeping you up to date.

For all your Custom Car & Motorcycle Parts, Manufacture and Welding / Repairs
Don`t forget to email or call us for all your custom made 1 off bespoke items.

Alloy welding / repairs, custom parts, Welding Instruction.

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