Monday 6 May 2019

Making an Exhaust Silencer

It has been quite a while since I updated this! Apologies. I need to be more diligent in posting updates.

During my last track day of 2017, the exhaust silencer on the TSR system suffered a mild failure where the perforated tube broke off from the main body and dropped down into the link pipe.

I treated this failure as a perfect opportunity to get a new silencer for the bike. I had thought that the silencer that came with the TSR system looked tired and was also too long to suit the look of the bike.

Naturally, option #1 was to purchase a ready made exhaust silencer from an aftermarket supplier and do a straight swap. Unfortunately, I found that the entry diameter for the TSR silencer is not very common (45mm) and while it was possible to purchase a direct fit silencer from one or two aftermarket manufacturers, all the exhaust designs were either far too short or had far too large an exit diameter to suit my taste. I did not want the silencer to look like a race style or a stubby.

Option #2 was to request one of the UK-based exhaust manufacturers to make a silencer with a bespoke entry design to suit the TSR link pipe. This seemed like a good route to begin with but as the design progressed, it became clear that the entry pipe design would be compromised by an external diameter change to allow the manufacturer's standard tooling to fit. The silencer would have had a swaged neck in the entry pipe which I felt would have looked unsightly on the finished product.

Option #3 was to attempt to repair the original silencer myself. I found a local supplier from whom I could purchase carbon tube in the correct diameter (also not standard) as well as the perforated tube and packing material for reasonable cost so the decision was made to have a go at doing it myself.

The optimum aesthetic length of the silencer was chosen by applying some basic photoshop "skills" to a photo of the bike and I decided to reduce the silencer length from 450mm to 350mm. This made the silencer look much more in proportion to the rest of the bike in my opinion but without making it look like a short stubby silencer.


When the old TSR silencer was dismantled, a few items stuck out as needing to be changed.

  1. The rivet holes in the old end caps had been damaged so most were oversize. To provide a better surface for the rivets to hold on to, a new strip of stainless steel would be added inside the end caps
  2. The old perforated tube was smaller than the silencer entry diameter and was only tack welded to the end cap in 2 places. It was also not supported at the exit end of the silencer which allowed it to vibrate and eventually break the tack welds and fall down into the link pipe. I sized the replacement perforated tube to be nicely supported on the exit end. As this still left the diameter of the perforated tube smaller than the entry diameter, I flared the end of the perforated tube to match and welded it fully around its circumference.
  3. The sleeve of the TSR silencer had been riveted directly to the end caps. I wanted to add rivet straps at each end both to provide a barrier between the rivets and the carbon sleeve and to provide a decorative finish to the silencer.

First the silencer assembly was modelled in 3D to ensure all parts fit as intended.

Modelling the exhaust assembly allowed me to get the rivet straps just right. The profile was laser cut from stainless steel sheet and bent into shape.

The perforated tube was flared and welded to the entry cap.

 The silencer was first dry assembled using clecos and test fitted to the bike.

Then the parts were riveted together.

And the packing material added.

Overall, the repaired silencer looks much better in my opinion and makes for a cleaner look than the old TSR silencer. The sound from the exhaust is not significantly different from before so that is a plus. There are a few things I would improve on or do differently if I was to do the job again but I am happy with the end result.


Unknown said...

Fantastic build thread. Well done. A lot of work involved, probably more than most realise.
Also, I can't help but notice your USD forks & radial calipers. Can you reveal what bike they came from and what you had to do to fit them please?

motthomas said...

Thanks for the kind words. Yep, there has been a lot of work put into this bike over the years! Probably more than I would like to recall.
I thought I had done a post on the front end conversion but it looks like I haven't so apologies for that. I will do a proper post on it in the near future. In the meantime though here is a brief rundown of the front end.
Stock MC22 wheel, CBR900RR discs, GSXR750 K4 forks, axle & triple clamps, GSXR1000 K3 calipers, B14 R1 master cylinder. To make it all work I had to fit different wheel bearings & seals, make a set of spacers for the axle, fit different headstock bearings & find a little clearance inside the front fairing. I will put more details & photos in a seperate post.