Honda CT90 Engine Reassembly

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I have one 1971 CT90 where I was going to rebuild the clutch because the kickstarter just wasn't turning over the engine like it used too,  and I also had a Big Bore kit from DrATV that I wanted to install. My intent was to just do the top end and rebuild the clutch with new disks, but when I opened up the cases to rebuild the clutch pack I found a slick black slime in the bottom of the case.  I didn't like the idea that there could be black slime in the rest of the engine, so I decided to disassemble the entire engine to make sure I cleaned everything out.  Since I was tearing everything apart I thought I would document step by step how everything goes back together in this post in case others were interested in knowing what the inner workings of a CT90 engine look like. Links to Related Posts: My Honda CT90 Clutch and Headset Nut Tool Cut Away of a CT90 Engine - CT90 Engine Exposed! Repairing Damaged CT90 Spark Plug Threads Using a Time-Sert Thread Insert CT90 Clutch P
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Cleaning CT90 Oil Passages

If you do tear into your CT90's engine to replace a piston or do other work it is always a good idea to take a little more time and make sure any and all oil passages are clean and clear before reassembling the motor. An example would be a part like the overhead cam where each of the cam lobes and bearing journals have a hole where oil is provided to the surface while the engine is running.  Oil gets to each of these holes from a bore that starts at the left end of the cam shaft in the picture below and runs to just underneath the hole that is visible in the right most bearing journal. When you have a part like this out of the engine you really need to make sure that there is no dried up crud in the bore or in one of the oil supply holes and you should be able to look down the bore and see light coming through each of the oil supply holes.





Helpful Links (Shop Manuals, Wire Diagram, Model Information, etc.)

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