1974 Ossa MAR

[Bennyonions]

Hi All,

Recently acquired a 1974 Ossa MAR, the whole thing is wreck so have stripped it right down. In short I cracked a crank case separating and am now looking to replace the right side case. I bought a nice cheap pioneer case but the only difference seemed to be the size of the crank webs as this chamber is 5mm smaller in diameter than that of the MAR, I have since bought an MAR case 1972 and again 5mm too small. Can Anyone tell me what year/model may correspond with the size difference other than 1974? Engine and frame match.

Put me out of my misery please..

Benny

[woody]

Sounds as though you may have a case from an earlier model Pioneer as most early Ossas had small crank assemblies. The early MAR - MK1 from 72/73, engine number begins 34 - also had a smaller crank assembly than the MK2 onwards - yours will be a NK2 as it's 74. As it is a 74 model the layshaft will run in bronze bushes so you need one from 74 - 76 engine, in late 76/77 the layshaft assembly was changed to run in needle rollers not bushes and although the shafts look identical they are slightly different in length and diameter so won't interchange (they might assemble but the gearbox won't work properly)

You need an engine from a MAR that begins  21, 22 or 23.  I don't know much about Explorer specs but think one beginning 44 or 45 might match the MAR but not sure - if you could find one as they're rare in UK.

Ossa ID chart here with chassis numbers (applies to engine also as they're the same)

http://ossa.2y.net/ossa/reference/ossaref.html

[owlit]

Any chance you could get your case welded, I'm sure someone will know someone who specialises in this kind of work?