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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How to Paint Honda CT90 Side Cases

I am in the process of installing a DrATV Big Bore kit on a 1971 CT90 that I own and I am also replacing the clutch disks at the same time, so since I was into the engine that far I figured I'd pull the other side cases and clean them up and paint all three side case that came originally painted from Honda.

This is the first time I have painted the side cases on one of my motorcycles, so I spent a little time searching the web to see what other people were doing as far as what paint to use. T settled on using the self etching primer and paint color shown in the picture below.




For the primer I used Dupli-Color EDAP16907 General Purpose Self-Etching Primer that I purchased on Amazon at the following link.  For the final color I ended up using Dupli-Color BHA0910 Arctic Silver Metallic Honda Perfect Match Automotive Paint that I also purchased at Amazon at the following link.  In the end I was happy with both of the paints I selected and I think the Arctic Silver matched the original paint color almost perfectly.

To prep the cases for paint I first cleaned and degreased the cases and then the next step was to strip the old original remaining silver paint from the cases. I first used Citrisstrip stripping gel that I had in my shop and it had absolutely no effect at all even after leaving it on the cases overnight.  I didn't feel like buying a can of a harsher paint stripper, so I resorted to using abrasives like 3M Scotch Brite also available at Amazon to remove the old paint which worked well.


With the old paint removed I wiped the parts down with alcohol to really get the surfaces clean and oil free and then I used blue painters tape to mask off all the sealing surfaces and other features I didn't want to get paint on.


With all the surfaces masked off, I then did a final alcohol wipe and let the parts dry and then applied several light coats of the primer.  The coat of primer should be on the light side as you are just looking for it to provide a good bond to the aluminum cases and then a great surface for the final coat of Arctic Silver to bond too.


I then applied the Arctic Silver in several light coats until I was happy with the coverage.


Once the parts were thoroughly dry, I removed the blue tape and I am pretty happy with the results.


I don't plan on applying a clear top coat as I like the look of the satin finish and don't really want a glossy look even though it would probably be more durable.

I didn't find the overall process all that difficult and I have plenty of paint left over, so I plan on doing the cases on some of my other CT90's following this process because I really like how these parts turned out.  Here is another set of cases I painted using the same process from a CT200 engine I am currently working on.



This is a nice simple process that will really refresh the look of your engine side cases.

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

Link to page with listing of CT90 parts available on Amazon



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