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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 Cl...
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More 3D Printed Part Design that can be used on a Honda CT90

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I've been having fun modeling a number of Honda CT90 parts and then printing them on my printer. and I thought I would share them here along with links to .stl files in case others wanted print parts for their own individual use. To create all of the parts I share below, I first created a 3D model in my ViaCad 2D/3D modeling program. Ignition Switch Access Hole Plug The first part I will share is my design for the rubber plug that goes in the hole where the wires from the ignition switch exit. I have printed this plug using SainSmart TPU filament which is flexible enough so the plug can be installed, but it is not near as flexible as a new stock rubber plug, but much more flexible than a 50 year old rock hard stock rubber plug. Here is the link to the .stl file at PrusaPrinters for the ignition hole plug.
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A 3D Printed CT90 Valve Spring Compression Tool

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 Since I picked up a 3D printer this Christmas, I've really found that it's a great tool, especially if you have a good 3D modeling program on your computer and reasonable skills to be able to design the part you would like to print. For a limited time I am including for free one of my prototype valve spring compression tools that I describe below with the purchase of my clutch holding tool available here at this link . My fundamental problem has been that I keep coming up with new designs I would like to print and get them 90% complete, before I get another idea and I'm off on another tangent (such is the life of a retired guy...). One of those designs is a Valve Spring Compression tool to use on a Honda CT90.   I've been using a C-Clamp and simple piece of tubing as my valve spring compression tool up until now and it always works and gets the job done.  I've done a post here at my blog on the C-Clamp tool here at this li...
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A 3D Printed Rear Airbox Snorkel for use on a Honda CT90 K1

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One of the other parts I recently modeled and made a 3D print of is the rubber Snorkel/boot that attaches to the rear of the 1969 K1 CT90's airbox, and that resides in the battery compartment area in the frame when the airbox is installed. Here is a picture of the model I made in ViaCad 2D/3D. The following are a couple of photos of the snorkel that I printed using a flexible TPU filament next to the stock rubber snorkel that I removed from the airbox. The 3D printed snorkel has a nice snow fit when it is mounted to the cylindrical feature on the airbox. Here is the link to the .stl file for the snorkel at Prusaprints I hope you found this information useful! Helpful Links  (Shop Manuals, Wire Diagram, Model Information, etc.) Link to page with listing of CT90 and CT200 parts available on Amazon
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A 3D Printed Carb to Air Filter Boot for use on a Honda CT90 K1

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I recently picked up my first 3D printer and now have an endless list of things I plan on making on the printer for my CT90's and other hobbies that I have. The 3D printer I picketed up is a Prusa i3 MK3S+ and I purchased it during a Black Friday sale Prusa had run last year.  I purchased the printer as a kit and it was a fun project in itself, but since I got the printer up and running, I've found it to be very capable and I am happy with my printer choice. One of my first projects was to design and print the a replacement for the rubber boot that goes between the carb and air filter on the 1969 CT90 K1.  I've owned sever K1's and I think I had only one where the boot hadn't fully degraded and wasn't falling apart like the one in the picture below. There are replacement boot/filter holders available, but they are almost $70.00 which is pretty pricey.  Most of the time the filter holder portion of the assembly is just fine and its just the rubber portion that ha...
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Aftermarket Honda CT90 Carburetor Drain Modification

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Relocating the Drain on a Aftermarket Honda CT90 Carburetor  I recently picked up an aftermarket carb for one of my CT90's off of eBay that is very similar in design to a Klein 556A carburetor except for one detail and that was the orientation of the drain fitting.  The drain fitting pointed straight down verses straight back and is a common issue with aftermarket CT90 carbs. Related Posts: Adjusting and Jetting a Honda CT90 Carburetor  Here is a picture with the old carb on the left and the new carb on the right.
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Honda CT90 and CT200 Gas Cap Teardown

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Honda CT90 and CT200 Gas Cap Teardown One of the most over looked elements of a Honda CT90 or CT200 fuel system is the gas cap used on the gas tank.  The gas cap plays a critical role and is designed to allow air to enter the tank and prevent a vacuum from forming as fuel is used by the engine as the CT90 uses a gravity feed fuel system.  While allowing the tank to vent air the gas cap also utilizes a labyrinth design to minimize the gas fumes that can escape from the tank. 
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Adjusting the Clutch on a Honda CT90

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I recently did the video at the link below on how to adjust the clutch on a Honda CT90.  The method I show in the video would apply to Honda CT200's and many other Hondas that have an automatic clutch. I hope you find the video helpful. Helpful Links  (Shop Manuals, Wire Diagram, Model Information, etc.) Link to page with listing of CT90 and CT200 parts available on Amazon
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