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

Two Quick Tips When Installing the Bearings in your Frame Headset

I was working on one of my CT90's this week and I had pulled the front forks to do some work that was needed and when reassembling the forks to the frame I thought I would share a couple of tips that I have found that help make the job go that much easier.

The first thing is to use a magnetic tool tray to hold the loose ball bearings.




The magnetic tool tray really helps as the ball bearings are prone to rolling out of whatever your holding them in and once they hit the garage floor they head off in directions unknown and are always a pain to find. With the magnetic tool tray you can group the bearings in the 21 that are needed for the top and bottom of the headset and they will stay put even if the tool tray is flipped upside down. Best of all you can sometimes find the magnetic tool trays as one of the free items at Harbor Freight!

The next tip is pretty common knowledge, but it is to apply grease to the bearing races in the headset before installing the ball bearings.


As shown in the photo above, apply a generous amount of grease around the entire circumference of the bearing cups (the photo above does not yet have all the grease installed so that you can still see the bearing race...).  Once you have the grease in place you can then begin to install the ball bearings by pushing each individual bearing into the grease and the grease will hold the bearings in place until the remaining ball bearings are installed.


This technique is nice in that it even will hold the ball bearings in place in the lower race of the headset which is facing down.


This is a simple trick but it really makes the job all that much easier.

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

Link to page with listing of CT90 parts available on Amazon

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