pmk Posted October 30, 2016 Report Share Posted October 30, 2016 I have taken the time to search and read about these bikes. I recently acquired a 1973 MAR and was wondering if the center exhaust section contains or contained at one point packing material, or is it baffled, or simply a small expansion chamber? I ask on account of wanting to clean it off carbon deposits internally and externally prep it for paint. Quote Link to comment Share on other sites More sharing options...
lineaway Posted October 30, 2016 Report Share Posted October 30, 2016 Just burn it out. Start a slow burn with a torch at one end, once burning continue with just a small amount of oxygen. You can see it`s progress from the outside of the pipe. Needless to say, do it in an open area away from the neighbors. Would not worry about the inner pipe. Quote Link to comment Share on other sites More sharing options...
bondy Posted October 30, 2016 Report Share Posted October 30, 2016 just done mine its a baffel plate dose not need repackiing i did repack the rear section. Quote Link to comment Share on other sites More sharing options...
woody Posted October 30, 2016 Report Share Posted October 30, 2016 The centre silencer on a MAR isn't baffle plate, it contains packing around a perforated tube. Only the rear silencer on a MAR is baffled. The packing may either have disappeared completely or be full of gunge. Using a torch won't do anything as the only way to restore the innards to proper working order on one of these (assuming that's what's needed) is to cut it open, remove what's left of the original packing which is also wrapped in wire, clean out the holes in the tube if necessary, then repack it and weld back together. 1 Quote Link to comment Share on other sites More sharing options...
pmk Posted October 31, 2016 Author Report Share Posted October 31, 2016 Bondy, when you say just did yours, what was accomplished? Quote Link to comment Share on other sites More sharing options...
pmk Posted October 31, 2016 Author Report Share Posted October 31, 2016 Woody, it does appear the midpipe was possibly packed with sound absorbing material when new. I questioned it being baffled as no light would pass through. After reading these replies, I found a nylon hose and fed it through the midpipe until it appeared at the opposite end. Apparently light would not pass on account of some kind of insect nest. The nylon hose cleared it, and now light can be seen through. If this possible runner does not become cost prohibitive to make into a daily rider, I will repack the pipe at that point. Currently working my way through the details to get it appart enough to ensure no damage is done if and when it starts. Thanks for the info on this topic and many others prior to it. Quote Link to comment Share on other sites More sharing options...
woody Posted October 31, 2016 Report Share Posted October 31, 2016 PMK - The rear silencer on a later TR77 is different from the MAR silencer. The TR77 rear silencer is stuffed full of wire wool and has two small exit holes underneath at its end. The centre boxes are the same, but on the TR77 the centre and rear are welded together whereas on the MAR they are seperate items Quote Link to comment Share on other sites More sharing options...
pmk Posted October 31, 2016 Author Report Share Posted October 31, 2016 This machine I got from the original owner. I learned from my friend that is building his 72 MAR, that we do not have the oem pickle silencer. It seems the setup, maybe just here in the USA was to replace the oem silencer with an aftermarket silencer / spark arrester. My friends 72 and this 73 both have identical silencer / spark arresters that can be easily repacked. Inspecting parts and learning OSSA quirkiness as I pull it apart to clean and evaluate. This old machine was last ridden years ago and has been stored outside for a while. Looks rough but is mostly there, but does need some TLC and someb parts. So far everything I had concerns about is coming apart pretty good after some penetrating oil. This machine has what is possibly a later model aliminim skidplate. Those slotted screws were not moving and the mud had cured like concrete so I did drill the heads off and all is apart no worse except needing screws. Next is removing the flywheel and ignition so I can get that area cleaned. Need to verify spark, carb looks good somaybe during the weekend I can get it running. Then go from there. Nice to work on a simpler bike, though I don't envy splitting the cases but can if needed, read about the shimming, seems tedious, but not difficulult. Quote Link to comment Share on other sites More sharing options...
pmk Posted October 31, 2016 Author Report Share Posted October 31, 2016 Wanted to that if needed, I will repack the midpipe, maybe mod it so it can be repacked easily as needed. No plans to build a restored MAR, I want a reliable rider. Would like quiet also as I hope to get it tagged for trail hopping and riding close to homes. Quote Link to comment Share on other sites More sharing options...
woody Posted October 31, 2016 Report Share Posted October 31, 2016 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 Quote Link to comment Share on other sites More sharing options...
woody Posted October 31, 2016 Report Share Posted October 31, 2016 The fibreglass sumpguard was replaced with the alloy version sometime in 73. Alloy version is better Quote Link to comment Share on other sites More sharing options...
bondy Posted October 31, 2016 Report Share Posted October 31, 2016 Sorry mine is the TR77 I was told the mid section never had packing so I just flushed out with Castaic soda then dried it out I repacked the rear I know you can buy the New mid section for the TR77 not sure if they are packed? Quote Link to comment Share on other sites More sharing options...
dhs10 Posted October 31, 2016 Report Share Posted October 31, 2016 Hello My mid section on my mar was rattly so I cut mine open neatly cut near the seem at the top and the center where there are two indentations. I found inside mine was a like it looked like a cross between plastic and melted exhaust packing materiel this was around a perforated tube I removed the what was left of the wading and welded the tube in place so it didn't rattle anymore then put a blow torch (plumbers torch) in one end it really flows through and soon gets red hot so watch out also it smokes like hell, once this is complete bend it back in place and weld up. I brought a silencer from in motion and welded the piece you get with the pipe and bracket onto the frame it looks and sounds good. Finally rubbed the rear sub frame loop from one suspension bracket to the other and spayed with smooth silver hamerite looks good as new, note: take your time in positioning the silencer it makes all the difference to the way it sits next to the frame and Rear Mudguard Quote Link to comment Share on other sites More sharing options...
scot taco Posted October 31, 2016 Report Share Posted October 31, 2016 Here in the states contact Alex Snoop for any help/advice or Ossa parts.If you have to split the cases just be careful and pay attention to what shim goes where and it probably wont need re-shimming unless you rebuild the crank.If so that would need to be checked for centering it in the cases. The MAR is the one trials bike that I really want,but haven,t found one close enough yet or at the right price. Good luck and chime in with any other questions. Quote Link to comment Share on other sites More sharing options...
pmk Posted October 31, 2016 Author Report Share Posted October 31, 2016 (edited) Here in the states contact Alex Snoop for any help/advice or Ossa parts.If you have to split the cases just be careful and pay attention to what shim goes where and it probably wont need re-shimming unless you rebuild the crank.If so that would need to be checked for centering it in the cases. The MAR is the one trials bike that I really want,but haven,t found one close enough yet or at the right price. Good luck and chime in with any other questions. Side tracking my own topic, I had no plans to buy an OSSA. My riding buddy always wanted one and picked one up last year. He has spent some time and dollars on what was supposedly a very good original bike. I recently noticed one and informed him of it as it had some original parts he needed, that one was reasonably inexpensive. So now he has two to build one creampuff and one rider. He thought it would be cool so we could ride together also. Still swayed more towards a semi modern trials bike, or more common TY250, I kept looking as the wife asked me to hold off a bit. We recently did a bicycle event that had us travel quite a distance but allowed us to see friends. While there, I was talking dirt bikes with a friend and told him about the MARs. He informed me he had one that he had bought new in 1972. The next morning at breakfast he insisted I drive to his house and take it home with me. So it made a 1000 mile trip. His wife told my wife that if our Tacoma pickup was not full with a bicycle and now an MAR she would have me take home more dirt bikes... He knew it was going to a good home and it would either be made into a rider or have parts pulled for the creampuff. Trying to get it where I feel comfortable to start it and cause no damage. Just takes time. Edited October 31, 2016 by pmk 1 Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.