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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Light Rust Removal from Chrome Plated Parts

Something that you'll run into with almost any CT90 project bike that you pick up is having to deal with light rust on the parts that are chrome plated.  With these parts you can't simple remove the rust by an abrasive means like you would on a painted part of the bike as you would destroy the chrome, so you need to take a more gentle approach to try and remove the rust, but not do any damage to the chrome plating.

There was a recent exchange on the Honda CT 90 Owners Facebook group that addressed this very question and everyone who participated provided there own approach for removing light rust.  There were a lot of great suggestions so I thought I would share them here.



I have used a few of the methods described below with some success, but if you do try any of the methods below star small and see if it is working for you and the proceed at your own risk.

1. Use Mothers metal polish

2. Use Loctite 1381191 Naval Jelly Rust Remover

3. Use 0000 steel wool and Wd-40. Only use 0000 steel wool and nothing any more abrasive or courser.

4. Use Diet Coke and wadded up aluminum foil

5. Use Wd-40 and wadded up aluminum foil

6. Use Never Dull

8. Use soft aluminum sheet metal cut into the shape of a butter knife blade (rounded off) to scrape off the flaky rust and then follow up with chrome polish

9. Use 0000 Steel Wool and phosphoric acid mixed 4:1 with water. Again make sure to only use 0000 steel wool.

10. Wadded up aluminum foil ball and Windex

11. Use a soft brass bristle brush

12. Use bronze wool

13. Soak in evaporust

14. Use vinegar and wadded up aluminum foil

All these methods require a little elbow grease, but if you take your time its amazing good you can get some very questionable parts to look.

Once you have removed the light rust from your chrome plated parts its always good to follow up with some sort of automotive wax to help fill in the pits and micro cracks that can exist in chrome to help prevent the rust from coming back.

If you are looking to try a remove heavier rust from non chrome plated  parts on your CT90 you might want to take a look at the post I made here on methods to use for heavy rust.


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

Link to page with listing of CT90 parts available on Amazon




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