You can usually run a Mk1 black rad on a later engine which had a Mk2 silver rad or even a Mk3 silver rad with flap. The main issue is the central rad support to the engine, the black rad has a single rod across it which fixes to a small rubber bobbin which in turn fixes to an angle bracket which fixes to 3 of the 4 screws which hold the reed block on. The issue is one of these fixing usually has the seal running through it. I have a very early 1998 senior max black rad and the angle bracket is not there, in place of it is a flat strap which blots to the top of the cylinder via the big hole above the reed block housing - a long M8 bolts runs through this and bolts the flat plate to it. You could bolt the black rad to this. Most upgrade to silver Mk2 or 3 rads anyway unless they have spare black rads - as me - why bother if you have two good black rads- apart from black rads are not MSA legal now - another way of Rotax forcing you to buy new parts!!
If you want to go from black rad to silver Mk2, you just need the mounting bracket that runs along the engine side of the rad and an M8 spacer nut or just a spacer and the correct length bolt to fix through the large hole above the reed block.
Mk3 rads have a rod just for that rad which fixes directly to the end of a long M8 bolt running through the large hole above the reed block inserted from the transfer gear side of the engine.
Mk1 rads also ran with a fixed ally 90 elbow out the top of the cylinder head cap and a straight hose pipe and similar to the bottom into the crankcase. But you can swap pipe to and from to suit between different rad types. Don't try to put the 90 degree top hose pipe directly onto the stub in the cylinder head cap if you unscrews the 90 ally elbow from the Mk 1 cap as the stub doesn't have the bulge on it's lip to stop the pipe slipping off.
In summary you can use any rad on any engine you just need the correct brackets, bolts and pipes.
Unless you are racing in MSA where you can't use a black rad.
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Rotax Junior rad advice please by 'abarth595' (24 Jul 2015 @ 16:44)
