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...
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A 3D Printed Seal for use on a Honda CT90 K2 and Later Air Filter Housing

One part that is not readily available for the Honda CT90 is the seal that fits in the groove at the rear edge of the main air filter housing on K2 and later CT90 models.  

I have been having success using TPU to print basic seals for other applications and thought it would be a good material to make this seal for the air filter housing.

Using ViaCad Pro version 12, I came up with a design and then printed it out using TPU.  The picture below is of the TPU 3D printed seal on the left and a stock Honda rubber seal on the right.

While the TPU printed seal isn't as compliant as the stock rubber seal, it is soft enough and I think works well for this application.  I designed the seal to have a slightly snug fit when it is installed as shown in the picture below.


If you would like to print this seal, I have uploaded an .stl file here at this link at Prusaprinters

Prusaprinters has a new rewards system where you can earn free rolls of 3D printing filament based on the number of designs you post, downloads, and the number of likes your designs receive, so based on that incentive, I no longer will be uploading files to Thingiverse.

If you do go and download this file at Prusaprinters, I would appreciate if you could also "like" my design as getting a roll of free filament really helps make it easier for me to come up with and share designs like this one for the CT90.

I haven't tried this seal out yet on a Honda CT110 air filter housing, but I think there is a good chance it will fit.


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