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

CT90 and CT200 Axle Information

When I was working on some of my first CT90's and buying parts off of eBay I ended up buying axles that were not correct for the bike because the eBay ad descriptions weren't always clear and I at the time really didn't understand that there were differences in the axles between the various years of CT90's and CT200's. Since I have a bunch of parts setting around from previous project bikes, I thought I would share a few photos and a little info to help someone else trying to pick up the correct axle for their CT90 project.  If I missed something with the info I am providing below, please feel free to comment.

From what I have seen CT90 axles can be broken into three groups: CT200's, early CT90's K0 thru K1, and everything K2 and on.

Here is a picture of the three groups of axles with the CT200 axles at the top of the photo, the K0 to K1 in the middle, and the K2 and on on the bottom. The rear axle is the top axle in each group and I have also included the correct spacer/collar and nut used on each axle.

Information on Honda CT200 and CT90 axles


I pulled together the table below to provide some basic dimensions to help tell the difference between the axles, nuts, and spacers.



Here is a larger picture of the CT200 axles, spacers, and nuts:


Here is a larger picture of the CT90 K0 to K1 axles, spacers, and nuts:


And here is a larger picture of the CT90 K2 and on axles, spacers, and nuts:


I hope this info is helpful to others searching for the correct axle hardware for their current or future CT90 project!

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




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