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

A 3D Printed CT90 Valve Spring Compression Tool

 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 link.

I had an idea and used my ViaCad 2D/3D to model the two parts below that make up the valve spring compressor design. 



The idea behind the design is that the rightmost part in the picture above acts like a rocker arm and is rotated when a cam profile on the lift part is rotated by the integral lever on that part.


I went through a number of different configurations of the designs until I found one that worked just right. The challenge with the design is that you have to create enough travel to compress the spring far enough so the keepers can be removed, but the have the right profile so that when the pressure is released off the spring that it doesn't clamp the tool in the head to where it can't be removed.

In the end I arrived at the design which consists of the two parts shown in the picture below.


I also made a short video at the link below to show how the tool actually works in use.


As I show in the video, the part isn't 100% ready for prime time.  The design works just fine, but I have had a failure or two after 10 or 15 uses, so it isn't as robust as I would like.  Durability isn't really an issue with a 3D printed tool like this if you have your own printer as you can just print a new tool.  


I plan on looking at changing some of the internal printing settings to increase the percent fill or add additional solid layers throughout the design.  The current parts I have printed have been made with PETG and I may look at picking up a spool of nylon filament to see if I can get a significant increase in strength.

I'll try and update this post when I get to a final design/material configuration, but I think I'm 90 to 95% of the way there.

I hope you found this interesting and maybe this will spark a few similar designs from others who have 3D printers.

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


Comments

  1. I admire your ingenuity, Michael! Is it worth-ed to have it patented? Good luck!

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  2. Do you have a link to what it takes to print out these parts? My son has several 3D printers in his shop and could likely whip out a set for me.

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    Replies
    1. Hi Richard, I haven't yet decided if or when I am going to release the .stl files for these parts. If I do I will update this post and the .stl file would be on Thingiverse, so if you follow me there you would get notified when the file gets up loaded. Thanks for the question, Mike

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  3. Hey Mike, Have you been working on this project? And is there any possibility of me printing one myself? I'm from the Netherlands so ordering one straight from you isn't a possibility for me anyways :"). Loving the work man, keep it up!!

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