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

Making a Basic Vinyl CT90 Seat Cover

I am always looking for a way to save a few bucks and I get a lot of enjoyment out of doing things myself, so I have a few CT90's that need seats and in a previous post I showed an approach to make your own seat foam/cushion, so I decided to go on and make covers for the CT90 seats I previously made a cushions for. While I have used a sewing machine a time or two in the past, this will be my first time trying to make a seat cover, so I look at this as a learning experience (i.e. I don't plan on my first seat cover being perfect...).

Here is a picture of one of the seats I will be making a cover for.





You'll notice that I won't be using black vinyl for the seat cover and that is because I have a roll of about eight yards of grey vinyl sitting in my attic, so since I am just getting my feet wet with making seat covers, I can't see spending the money on black vinyl when I may screw up my first couple of attempts.  These seats will also be going on bikes that are good runners, but function is more important than looks.


The first thing I did was to make a simple pattern for the top of the seat using a scrap piece of vinyl. I only made the pattern for half of the top of the seat as it will make it easier to make the final piece of vinyl symmetric. I had the pattern hang over the edge of the foam and made a line about a 1/2 an inch in that will be the seam allowance for when I sew the cover together.


I took the patten I made and then laid it on the back side of a piece of vinyl and traced the first half and then flopped it over and traced the other half of the top piece of the seat cover.



I cut out the piece and set it on the seat foam so you have an idea how much the final piece hangs over the edge of the foam.



I next needed a piece of vinyl to run around the perimeter of the seat, so I eyeballed that a six inch wide piece should do the trick buy giving me enough material to have about a 1/2 and inch of seam allowance when I sew it to the top piece and still have enough to wrap around the bottom edge of the seat and pick up the barbs on the seat base plate that will hold the fabric on.  I cut two six inch wide strips (I'm make two seat covers...) the full width of the roll of vinyl that I have that is about 54 inches wide.

I texted took one of those strips and then wrapped it around the perimeter of the seat foam with the backside of the vinyl facing out and then pinch the two ends of the strip gently together near the front of the seat where I plan on having the seam located and then made a vertical mark on each end of the strip where it was being pinched. I then cut off the excess on each end of the strip leaving a couple of inches beyond the mark I had made (be generous here as there is no need to cut near the mark you would make).



Now that I had the two pieces of vinyl needed for the seat cover, I next focused on cutting out batting to use on the top piece of the cover to give it a quilted feel.  I picked up a small roll of 1/2 inch thick batting from the fabric store and then used the top part of the seat cover as a pattern to cut out the piece I needed for each seat cover I am making.





Now its time to get down to sew all of these pieces together into a seat cover. The first thing to sew is the batting to the top of the seat cover. I laid the batting on the back side of the vinyl and sewed the two pieces together starting from the center and then working my way to each end sewing about and inch and a quarter from the last seam I sewed across the seat cover.  I eyeballed the gap, but you could just as easily made parallel lines in the batting to follow. The thread I used was a heavy duty polyester thread that I picked up at the fabric store.



And here is what the top piece looked like on the finished side when you're all done.


The next part is where it gets a little more complicated. to attached the side piece to the top part of the cover you need to pin the side piece to the top starting at the front of the top piece and then work your way around until you end up where you started with the back side of the vinyl and the batting facing out.


Next you sew around the area you just pinned together staying a little less than a half an inch in from the edge and work your way around starting about a half an inch from the end where you first pinned to almost where you ended, but stop about a half an inch from the end. Take your time with this step in the process.



Once I sewed 95% pf the perimeter, I then focused on sewing the two ends of the side piece together. To sew the two ends together I gentle brought them together where they would end up naturally now that the side was sewn to the top of the seat cover, pinched them together and sewed across the two ends.  With the ends sewn together I cut off the excess material leaving about a half an inch and then folded that to one side and then sewed the flap from the finished side of the vinyl as shown in the pictures below (its a little ugly, but it will work...). The last step in this part of the process is to go back and finishing sewing the last little bit of the side piece to the top piece over the seam you just made to finish sewing the top to the side of the seat cover.



The next part is a little involved and what you are going to do from the inside of the seat cover is to lay the small flange of the seat top on the side of the seat cover and then while pulling lightly on the side of the seat cover, sew around the perimeter of the seat for a second time.


Which should result in your seat cover ending up looking like this and the sewing part of the project is complete.


Your finished seat cover may be slightly smaller then the foam on your seat, but that is ok as stretching the seat cover over the seat/foam will give you a nicer fit.



The next step is to install the cover on your seat, but first make sure you have to old rubber edge that went around the rim of your seat pan that the vinyl will be stretched over.  You need to have this otherwise your seat won't last very long.  If you don't have it, DrATV sells some seat pan material or you can try what I used, which is a universal rubber U cannel weather striping that I picked up off of Amazon that was only about $8.00 for about twenty feet (I am doing several seats, so I needed a bunch...).


Run whatever material you end up getting around the edge of the seat pan and gluing it will help hold it in place when you go to install the seat cover.


The next step is to slip your seat cover over your seat and pull around the edges until the seat is all the way on to your seat cover.  Depending on the final size of your seat cover this may take a little bit of work, but the vinyl will stretch to some degree, so keep at it until its all the way on and make sure to fix your rubber edging if it slipped off during this step of the process.


Starting at one side or the other, gently pull the vinyl snug and poke it over the spikes on the inside rim of the seat pan and then fold that spike down. I do one spike at a time working back and forth on each side of the seat, working from near the front to the back and then I finish up at the very front as you may need to trim some excess material away it that location.



If you don't have the stainless steel trim ring that came with the seat your basically done.


If you do have the trim ring then you have a few more steps to go to complete the seat assembly.  The first thing to do is get a awl or something similar and then find the holes in the seat pan buy gently poking around on the inside of the seat pan and then poke a hole through both layers of the vinyl for all five hole locations (the seat in the following pictures may look slightly different then the one I used for the other pictures above as it is the second of the two seat I was recovering).


Slip your screws into your trim and then through the holes you just made, install your nuts, and your done and its ready to be installed back on your CT90!



Related Posts:


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

Link to page with listing of CT90 parts available on Amazon

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