I have a TR77 there is no packing in the mid box on that model.

Rear silencer on my bike is an alloy one from a mx bike cut down as described by woody, noise level is right and the bike rides very smoothly.

Ellastone off road is the place for a s/h back box.

After getting it running today, it is appaarent that the exhaust note is a bit harsh. Without doubt the spark arrester / silencer needs repacking.

As for the mid pipe, I plan to rework that and repack it also.

On 10/31/2016 at 1:45 PM, woody said:

The MAR was introduced in 72 and didn't have a rear silencer. They were a bit crackly... The pickle silencer appeared sometime during 73 so both 72 and earlier 73 bikes had no tail pipe

 

You can buy new pickle silencers, I haven't tried one but the originals did mute the exhaust effectively

 

Alternatively, you could easily make an effective silencer that doesn't spoil the looks of the bike. I used an old YZ250 2-stroke rear silencer and cut the body to the required length, re-placed the internals with a 25mm straight through perforated tube with new wadding and replaced (or sleeve down) the inlet and outlets with 25mm  (YZ inlet, outlet and core is 30mm if I remember correctly)

 

I have these on my 250 and 310 MARs and they work very well

 

I wouldn't bother repacking the centre section until you've run the bike as it's not a nice job and no point doing it if it doesn't need it. If it does need packing, as well as being a bit loud the bike will also be a bit lumpy off pilot as a well packed silencer makes them run very smooth. There are few bikes as smooth as a MAR off pilot

 

Example of type of silencer body here

 

http://www.ebay.co.uk/itm/2005-YAMAHA-YZ-250-SILENCER-PROCIRCUIT-A-05-YZ250-TWO-STROKES-/142162425062?hash=item21198a74e6:g:XSUAAOSw5cNYEkka

Woody, the OSSA is coming along.  Regarding the exhaust center section, I am going to repack it.

I have a section of stainless automotive exhaust tubing that matches the OSSA center pipe diameter.  Planning to make an access cover that is removable, allowing repacking without any welding required.  This will also allow repacking over time if needed and will be an easier task.

In regards to the oem OSSA packing material, do you know if it was a stainless steel wool or fibreglass material?  I have access to both.

Thanks

It was some kind of fibre packing originally, I just use silent sport wool for mine

Yesterday, I began the repacking of the 1973 OSSA MAR midpipe.

The task how I am doing it involved cutting a "window" into the round chamber section, removing the original packing, then making a cover to be fastened with bolts.  The cover will be sealed and allow repacking next time to be pretty easy.

Inside the the midpipe, the original packing is a crazy but long term packing material.  Placed against the perforated baffle tube is a fine steel wire matting.  Not steel wool, but rather a non woven almost like a spool wrapped method of placing the fine steel wires around the baffle.  Next, the fine wire is held in place by many wraps of a large wire.  This offers no true sound deadening, simply secured the fine wire mat onto the baffle tube.  Downside of the large wire is removing it.  Next, wrapped around the fine wire is a layer of fibreglass packing material.  The fibreglass is placed over the fine wires and then rests against the midpipe outer steel wall.

Overall, I would say the pipe I have was fine as it was.  Unfortunately, there is no easy way to know if the packing is intact, oil soaked, or blown out.

I carefully decided where to cut the access window, avoiding any issues when the pipe is mounted.  I favored to the right side, to avoid contact of the window cover with frame or left side panel.

I plan to repack with all fibreglass packing material, stuffing it into the midpipe.

Removal of the oem wire material took quite a while.  The forward end of the midpipe where they crimped the midpipe to clear the frame still retains a small amount of oem material.  When crimped, the oem sound packing is now wedge between the baffle and midpipe outer shell.

 

 

 

Edited May 23, 20179 yr by pmk

Got the exhaust mostly done today.  Fabricated cover, drilled and verified cover was secure.  Washed and applied OSPHO to treat bare steel, then gave it a quick paint job.  Packed with silencer packing, if I like the tone, I will remove the cover and seal it, then reinstall the cover and final paint.  The cover was made from Stainless tubing, the fasteners are aircraft stuff I had around, we call them clip nuts.  The screws are 8/32 or about 4mm and thread into the locknut portion of the clip nut.

 

 

Yes, I could have used Rivnuts or one of the variations of that type insert.  I have easy access to those also, plus have various install tools for them.

ReasonsI opted not to use them.  The installation hole is larger than that of a clip nut, unless I used flushhead style, the head thickness is more than the clipnut.  Clipnuts utilize all metal high temp locknuts, so there is minimal chance vibration could loosen the plate.  Clipnuts also allow greater fastener torque.  There are more reasons, but I considered even going with steel pop rivets that could be drilled out next time, but continually returned to the bag of 8/32 clipnuts.

Cool video, looks to be some type of aircraft builder training video.

Clipnuts are kind of common from places like Aircraft Spruce and Specialty.   Ot sure on cost, but should not be too bad.

Edited May 30, 20179 yr by pmk