chappo Posted May 8, 2019 Report Share Posted May 8, 2019 I’ve done plenty of Bultacos but not one of these. Before I start cutting just wondered if anyone had any images of the exhaust internals from when they repacked theirs. Is it as important on these as the Bultacos to repack the front box for back pressure. Quote Link to comment Share on other sites More sharing options...
feetupfun Posted May 8, 2019 Report Share Posted May 8, 2019 Yes I've done it but it was a few years ago so the photos will be a fair way back in the forum. It was the first time mine had been apart. One of the boxes had metal wool packing and the other was mineral fibre. Can't remember which was which. I used mineral fibre in each and made new perforated tubes for one of them. Mine didn't run any better after the repack but was lighter and quieter. I notice that later model Montesa trials bikes of Spanish origin had a much longer header pipe than the 348 which may mean that having the front section packed at the right density where it is in contact with the perforated tubes could be important. Quote Link to comment Share on other sites More sharing options...
chappo Posted May 8, 2019 Author Report Share Posted May 8, 2019 Thanks feetupfun, I’ll have a better look through the old posts. ?? Quote Link to comment Share on other sites More sharing options...
chappo Posted May 8, 2019 Author Report Share Posted May 8, 2019 Thanks feetupfun, I’ll have a better look through the old posts. ?? Quote Link to comment Share on other sites More sharing options...
cleanorbust Posted May 8, 2019 Report Share Posted May 8, 2019 (edited) Sorry no photos, but easy enough to cut a rectangular window in the flat area on the back of the silencer with a dremel. Leave about a centimetre margin on the flat surface. The perforated tube will then be exposed - pull out any remaining packing and repack with modern loose packing material around the tube. Make up a rectangular plate from alloy sheet to cover the hole and fix in place with small self tapping screws into holes drilled along the 1 cm margin around the window. Seal with heat proof silicone. You then have a silencer with quick access for repacking in future. Repacking well worth it in my experience (Cota 247). Edited May 8, 2019 by cleanorbust 1 Quote Link to comment Share on other sites More sharing options...
2stroke4stroke Posted May 8, 2019 Report Share Posted May 8, 2019 I did both on my 348 back in the day, using roofing insulation, and it was a lot smoother afterwards. Quote Link to comment Share on other sites More sharing options...
barnesy Posted May 8, 2019 Report Share Posted May 8, 2019 Id be interested to hear how you get on Chappo as I'm considering doing the same on mine... Quote Link to comment Share on other sites More sharing options...
chappo Posted May 8, 2019 Author Report Share Posted May 8, 2019 (edited) 1 hour ago, barnesy said: Id be interested to hear how you get on Chappo as I'm considering doing the same on mine... I’ll try and remember Barnesy, it’s a couple of months before we’re at that stage, just stripped her. I’ll try and include some images as I don’t think there are any of the internals exposed in this forum. ?? Edited May 8, 2019 by chappo 2 Quote Link to comment Share on other sites More sharing options...
Twinshockandy Posted May 11, 2019 Report Share Posted May 11, 2019 On 5/8/2019 at 7:29 PM, barnesy said: Id be interested to hear how you get on Chappo as I'm considering doing the same on mine... Same here. 1 Quote Link to comment Share on other sites More sharing options...
chudder Posted December 20, 2020 Report Share Posted December 20, 2020 Thought I would repack the exhaust on my 348 as is suggested.Could see that it had been done before by the ring of weld around it. Cut a rectangular window out and found no sign of any packing and no baffles,just a straight through pipe! Not what I was expecting. What to do next? Who ever did it did a good job of it,just should have done it with baffles. Quote Link to comment Share on other sites More sharing options...
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