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

Product Review - CT90 Clutch Tool

CT90 Clutch Tool

I purchased this clutch tool off of eBay over a year ago and have now used it a number of times and its still going strong and I have been very happy with the purchase.  I mentioned the tool in a previous post related to working on your CT90 clutch, but thought I would share a few additional thoughts here.

To rebuild the clutch pack on a CT90 you first need to remove it and that process involves the removal of a special nut that requires a spanner tool to loosen it.  While it may be possible to remove the nut using a punch or some other backwoods mechanic method that stands a high chance of screwing something up, the right way is to purchase a spanner tool given how cheap they are on eBay.

I purchased this tool off of eBay for $6.55 and there are several sellers that offer this same tool for a similar price.   The tool is designed to work with two sizes of spanner nuts, 22 mm and 24 mm (what is needed for your CT90).




The three main features that are important with this type of tool are does it fit your wrench that will drive it, does it mate with the spanner nut you are trying to loosen or tighten, and is it strong enough that the tabs won't snap off or yield/bend over when torque is applied to either loosen or tighten the spanner nut that holds the clutch pack on your CT90.  In all three cases this tool performs well and gets the job done.

The tool has a square feature/hole broached in the center of the tool that I found to mate well with the standard 1/2 inch extensions I used to drive the tool using both a 1/2 inch ratchet or electric impact wrench.


As far as mating with the CT90 clutch spanner nut, I found the 24 mm end of the tool to always be able to be easily inserted to an installed spanner nut.  Here are a couple of shots of the tool and a spanner nut from a CT90 showing how the tool fits.



As far as the strength of the tangs on the tool go, I have used the tool a number of times now and have even driven it with my 1/2 inch electric impact wrench and have seen very little if any wear and tear on the tangs and no bending.  The tool seems to be made from a hardened steel and has held up well.

Overall I am very happy I bought this tool and would recommend it to anyone looking for a tool to help them remove the spanner nut that holds on the clutch pack of their CT90.

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

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