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 Cl...

1970 CT90 Headlight Switch Breakdown and Assembly

I was going through and cleaning up the right lever lever assembly that retains the throttle grip and also the headlight switch and thought I would share a few shots of the detail parts of the headlight switch and how it is assembled.

Here is an overall shot of all the components:





The key element of the headlight switch is the small plastic block that contains sliding contacts as is what moves an makes the different connections when you move the headlight switch lever.


The two sliding contacts are different in that one has four dimples and one has three.

And are assembled into the plastic block with the one with four dimples closest to the side of the plastic block with the small pin feature.



Another way to know you are assembling this correctly is that the sliding contact with four dimples runs on the family of five contacts at the end of the wire bundle and the sliding contact with three dimples mates up with the tree contacts.


I use a little dielectric grease on the sliding contacts when I build up the assembly.


Before I assemble the sliding switch into the lever housing I add a small amount of regular grease to the detent features that the ball bearing on the switch block interface with and I also put a small amount on the spring and ball.

When I assemble the switch into the lever housing I put the sliding contacts first then the switch block over the contacts and then the sting and ball into the switch block and with all of those parts pinched between my thumb and finger I slide it into the housing.

I then instal the switch lever making sure to include the very small bushing at the pivot end of the lever and then I install the lever screw and then the hold down plate.



I'll make sure and check at this point that the switch operates smoothly and then I'll install the other half of the lever assembly buy laying the wire harness in the groove and then install the small plate with the screw.

And then its ready to be installed with the throttle on the handle bars.

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

Link to page with listing of CT90 parts available on Amazon



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