pmk

When I got this machine, It had been sitting outdoors for a while. The tires were flat and the thing looks rough. The engine would not spin via turning by hand using the kickstarter initially. After a couple light attempts to just have it turn a little, it did come loose. My first thought was a stuck piston, but later turning the flywheel by hand, the engine is smooth. So I suspected and confirmed after removing the ignition side cover there had been some water inside it from sitting outside. Enough water to partially submerge the lower magnets and stator poles. These rusted and made the motor stuck. Fast forward, bike is home, pulled the flywheel and it certainly is not bare steel. There was very little reddish rust, mostly the white powder almost as if it was zinc or silver cadmium plated. Removing the corrosion, removed the coating. Currently, the flywheel is bare steel and coated with an oil to keep it from rusting. I had a look at various photos on the net after my initial post and most flywheels had a grayish color. Assuming the Motoplat fires the plug and the ignition is usable, I will probably have the flywheel and other various bits of hardware cad plated. Thanks for the replies. Still not disappointed, just some effort so far. Want to get it fired and ensure it runs compiling a list of needed items. Then pull the engine and chassis apart assuming it is viable to fix up vs part out.

My 1973 MAR has some corrosion on the flywheel and stator. With care, I have cleaned up the poles of the stator. To clean the corrosion from the flywheel I used abrasive cloth and cleaned the magnets and interior. I also used the abrasive cloth to clean the flywheel exterior. Removing the corrosion also removed whatever protective coating was there, so I ask, does anyone know what the oem finish was and what color a new flywheel would be.

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.

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.

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.

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.

Bondy, when you say just did yours, what was accomplished?

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.

Recently acquired a 1973 OSSA MAR from the original owner. Rough but mostly there. Not running and needs some attention. The MAR was not a planned machine to own, was looking more at a modern trials bike but this was offered to me knowing it was going to a good home. Time will tell if it is viable to fix up or is cost prohibitive. Always wanted a trials bike, hope to attend some of the Florida events, even if as a spectator.