RZ350 - Top End Disassembly
The first step to tearing down the motor is to remove the barrels. To do this is it is necessary to remove any remaining coolant in the system. You can either just turn the motor upside down if you have a helper (make sure the oil is drained first), maybe tip it on its side, or use the bleed bolts on the side of the barrels and let the coolant drain out. The main purpose of this is to get any coolant out of the head before it is removed.
.A coolant pipe from the cylinder head to the casing must be removed by disconnecting the neck from the head. Just remove the two allen head bolts and the neck should come free. If not you can giveit a small tap with a rubber mallet to break the seal.
The head is retained by 10 bolts through the head into the barrel studs.In order to guard against warping the head it is a good idea to loosen each bolt a 1/4 turn at a time until they are loose enough to undo by hand.
Each bolt has a washer beneath it. These washers and bolts can be saved for the rebuild.
The head can then be lifted off the barrel studs. This can be a little difficult if it has been a while since it has been removed. Another tap from a rubber mallet will break the seal.
The cylinder head usually comes off with the cylinder head gasket, The gasket can be removed from the head and tossed in the trash. You should always use a new head gasket when rebuilding.
The carburetors now have to be removed as the barrels are independent castings and the carbs connect them. Find the retaining clip on each side where the rubber intake boot goes around the carb casting. Loosen both the clips with a Phillips screwdriver....
...and pull the carbs free of the motor. You may have to wiggle them to get them out of the rubber boots.
From here you can either remove the balance tube between the two intake boots and leave them connected to the barrels, or remove the boots and pipe as a whole. I chose to remove them as a single unit by removing the 4 allen head bolts that hold the boots to the barrels.
This allows you to have a look at the conditions of the reed valves. The ones on this motor are not the stock stainless steel ones. I'll keep them around just in case, but I plan to go back to stock so I'll be replacing them.
The barrels are also connected by the power valve assembly. It is only necessary to remove the connector between the barrels to remove them, but I plan to remove the powervalves themselves so I have included the steps later in this section. Locate the coupler which is held in place with two small Phillips and loosen them both.
The coupler comes apart in two parts. The Haynes manual recommends replacing these Phillips bolts with allen head bolts becuase they can corrode easily due to their location. I'd second that but also recommend going with stainless steel ones.
Finally we get to the barrels themselves. Each barrel is held to the casing by four nuts at each corner of the barrel. Loosen and remove each nut completely.
The barrels are a tight fit on the casings and sometimes are a little tough to get off. If they are stuck in place do not try and lever them off with a screwdriver as it will mess up the gasket faces. Using the rubber mallet tap the barrel until a space opens up between the casing and the barrel.
Lift the barrel off the piston. Don't worry if the base gasket gets torn or destroyed. These should be replaced when the motor is rebuilt. The barrels clearly only go on in one direction so don't worry about marking which is left and which is right.
Follow the same process for the other cylinder and set them both aside for inspection and possible reworking.
If you plan to reuse the pistons mark them with a R and L for left and right. Each piston is unique to its bore after the motor has been broken in.
To remove the piston, pry out the wrist pin clips at either side. These are made from wire and can be levered out with a small screwdriver, but be carefull not to scratch the side of the piston.
The wrist pin can usually be pushed out by hand but a stubborn one may need a wrist pin puller tool. If you don't have access to one of these you can try to heat the piston with a hot wet towel, but do not try to bang it out with a hammer as you may bend the con rod.
Finally, remove the small end bearing from the eye at the end of the con rod.