This article describes the process of splitting the crankcases for the SWM TL350 Jumbo as part of the rebuild/restoration process. I’ve (currently) done it a couple of times; first to change the crankcase seals and subsequently to sort out locking gear problems
Initially I decided to split the crankcases in-order to change the crankcase seals. I followed the following process:
– remove the engine from the frame; there are three mount points, bottom-front, bottom-rear (through the swinging arm) and the top plate. I removed them in this order and you will need to take the spark plug and decompressor out of the head in order to remove the top plate
– remove the clutch cover and flywheel covers from the bike
– remove the flywheel, you’ll need the Rotax flywheel puller or a suitable home-made tool. Looking at state of the nut and the ignition coils om my Jumbo, someone didn’t use only a basic (ie a hammer and chisel). Make sure the woodruff key is retained (you may want to replace it).
– remove the stator plate,(see figure 1). Then remove the rear plate with the three screws (I needed an impact driver to remove the butchered screws). You can then take out the wires and then the stator plate.
– remove the head bolts, noting the location of the types of bolt. Remove the cylinder head. There are two hex bolts holding the barrel in place; it should be then be possible to lift the barrel off the piston.
– I removed the piston before splitting the cases, by removing one of the circlips from the piston and pushed out the gudgeon pin by hand.
– I decided not to remove the clutch assembly before splitting the cases; this was mainly due to not having a suitable tool, more on this later, but unless you are changing the crankshaft seals you shouldn’t need to remove crankshaft nut (A in the diagram). This nut seems to be some form of an interference fit; its bloody tight.
– remove the crankcase bolts; there are a set round the edge of the right-hand case and 5 by the crank shaft. The is one bolt on the left hand case.
– the using the pry-points on crankcase I started to level the crankcases apart and then using a soft headed hammer, then hit the RH end of the crankshaft. The crankcases should come apart fairly easily.
– the gear cluster remains with the RH crankcase (as the clutch is still in place, see figure above, mark B), with the gear selector remain in the LH case. This means that to put the cases back together, the gear cluster, selector drum and selectors will need to placed in the LH case, so that the gear change can be engaged prior to re-assembly.
– to remove the cluster, I then undid the clutch plate nuts and then the main clutch nut. starting by folding back the tab washer (the one on the Jumbo seems to be rather thick). I jammed by faithful 2p coin into the gear cluster and heated the nut to undo it. There is a special tool to hold the clutch basket AFAIK, but did see a trashed clutch basket (courtesy of Martin Matthews) which has made me wary of too much aggression in this area.
– you should then be able to remove the gear cluster, ensuring that you keep all the sprockets, washers, rollers etc in the right order.
My strip (and subsequent strip) of the engine was to change the crankshaft seals and then to resolve problems with the gear cluster and its tendency to lock. More of this later in a seperate article.