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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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Using a Spark Plug from my Subaru Outback on my CT90!

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 I was changing the spark plugs on my 2015 Subaru Outback the other day, which isn't the most enjoyable task, but while cleaning up and putting away my tools, I noticed that the old plugs I pulled out of my Subaru had the same M14x1.25 thread as what is used on the standard D8HA CT90 spark plug.
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A 3D Printed Points Cover for Use On a Honda CT90

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 I have a long list of items that I want to create designs for that can be 3D printed and one of those that I decided to do recently was to back engineer the aluminum points cover from a CT90 and create a model so that I could 3D print the cover. The points cover on a Honda CT90 is really just a vented dust cover to keep the points clean, so it seemed to be a natural to turn into a 3D printed part. Here is a picture of the final 3D part installed on one of my CT90's
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Using ChatGPT as a Tool to Help Work on Your Honda CT90

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 The artificial intelligence tool on the internet known as ChatGPT has been a hot topic in the news lately, so I thought I would go in and give it a try and ask it a few questions about Honda CT90's. I've just started to play around with ChatGPT, but my first impression is that I am going to find it a very useful tool going forward. The best thing about ChatGPT is that is answers the question you ask.  When you use a typical search engine like Google it tends to give you a page with responses that are more focused at trying to sell you something and it can be difficult to find a link with information that answers your question. With ChatGPT it simply tries to answer your specific question, nothing more and nothing less, as you'll see in some of the examples I share below. To actually use ChatGPT you need to go to the OpenAI website (OpenAI created ChatGPT) and create an account.   Here is a link to their webpage where you can set up an account. When you get to the webpage a
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How to Disassemble a CT90 Rear Shock Absorber

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 If you are going through and cleaning up your first CT90 rebuild project, one of the things that is not so obvious is how to disassemble the rear shock absorbers. The process is pretty straight forward and while it is possible to disassemble the shock absorber without any special tools I find it much easier to make a simple tool to compress the spring on the shock absorber.
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A 3D Printed Air Intake Boot for use on a Honda CT200

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 Recently someone on my Facebook page commented about a post I did where I shared information about a 3D printed air intake boot I designed for K0 CT90's and asked if I could design one for the CT200 and even offer to let me borrow an old CT200 air boot that had some issues to use to help construct a design. Related Posts: A 3D Printed Honda CT90 K0 Air Intake Boot Well I've actually had an old CT200 air boot on my desk for over six months as creating a 3D printed design has been on my list of things to do for quite some time. With the encouragement from the comment I received on Facebook, I sat down and created an initial design using my ViaCad 2D/3D Pro modeling software that I'm pretty happy with. Here is a picture of the 3D printed design I came up with and printed next to the stock Honda CT200 air boot.
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A 3D Printed Functional Rear Air Filter Housing for use on a Honda CT90 K2 and Later

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I have on and off been looking at trying to model or scan some of the different CT90 air filter housings so I could make 3D printed versions, but have had limited success.  Related Posts:  CT90 K2 and Later Air Filter Housing 3D Printed Seal  After some effort I was able to create a functional design of the rear portion of the air filter housings used on K2 and later CT90's.  The picture below is of the next to the last configuration that I designed and then printed during a trial fit on one of my bikes.
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A 3D Printed Seal for use on a Honda CT90 K2 and Later Air Filter Housing

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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.
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