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Part 4
Some things to know about re plating cylinders. Typically, Nikasil or a derivative (silicon carbide) of this is used. This stuff is super hard. Its used as it’s wearing surface is very good. The rings cannot be chromed faced as you cannot run two super hard surfaces against one another. The break in period is often talked about. Bedding in the rings. This is so misunderstood with Nikasil coated cylinders. Under a microscope, the surface will be full if high peaks and low valleys. The surface is extremely hard and does not wear, when compared to the ring faces that are a lot softer. So, when you have very rough surface finish, with lots of high peaks, you will wear away the ring faces and destroy the ring seal. Therefore, the surface finish must be of a certain number. The lower the number on most scales is a finer finish. The 3rd party company I have mentioned here have no clue on what the surface finish should be. So be careful. My advice is to ask an engine builder or the actual repair place for their advice, not a parts salesman.
You need to also check the cylinder heights to make sure they all match. If they dont’, they can be equaled by removing some material off the base. Also, now is the time to decide on any sealing system to be performed. This should have been included in your preplanning.
Pistons. These are easy to inspect for wear; the skirts should be unmarked and show no signs of trash sliding down the sides. If they do, they need replacing. If they look good, the next is to clean them. Removing all the carbon and dirt will show any signs of valve contact or head contact. Expect the pin bosses to need some help. Probably removing the burr made when you removed the clips. The pistons once cleaned need to be measured to make sure they are within spec. If they have a lot of time on them, it’s a good idea to have them checked for hardness. They do go soft over time with all the heat cycles. Most of the time these are replaced with a larger bore version. Ring lands need to be checked for wear as these become larger over time and the side clearance of the ring is an important dimension to hold otherwise you will have ring control issues especially when the piston is not under load. Pins sometimes show wear, and these should be carefully inspected as well. If new pistons are to be use, they will come with new pins and clips.
Next is the engine case assy. Before disassembly, and with the Cylinders removed, now can be a good time to have a general look over. Typically, this is the part that is covered with years of dirt and will require a lot of time to clean. You need to remove the chain housings and the rails. The rails are held in place by the bolts, on both sides, in the front of the engine case.
There are 13 Through bolts to undo. Two are hidden behind the Oil cooler, so be sure to remove this first. Be careful here, Oil will spill out all over the place. Undo all the 13 through bolts and all of the 8.00mm perimeter nuts. There are two nuts that need to be removed. The one on the outside of the 1/2/3 side of the case that clamps the case at the Intermediate shaft and the one down inside the chain housing on the same side of the case.
Splitting the case halves apart can be an issue. Glue, years of been together can make this hard. There is a tool that can be bought from a vendor that makes this easy I’m told. This needs to be added in your budget. Remember, tools like this may only have one time use. Go slow here and use gentle taps with a plastic mallet. Often the front of the case will split first as there are no dowel pins at that end. The rear Flywheel end has two dowel pins either side of the rear main bearing shells which makes the case harder to come apart. If you are doing this without any special tools, do not use a screwdriver to wedge the case apart. You will damage the sealing surfaces and increase the chance of an oil leak. Sometimes a piece of hard wood long enough to reach up through the arms of the engine stand can do the job. Position one end on the inside of the bell housing register and tap. It may take more than gentle tap but don’t go crazy here either. As soon as the case splits you may have to tap at each end to get the case to come apart front to back evenly. Lift off the case the 1/2/3 side and expose the Crank shaft and Oil pump assy.
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