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1965 Honda s90 rebuild

15K views 17 replies 11 participants last post by  mexmark 
#1 ·
I've been checking out other people's awesome projects for a while now, so I figured I should officially join the forum and post my project bike. It's a 1965 Honda s90 that I bought in Birmingham, AL for $220. It was in pretty rough shape with a good bit of parts missing.

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I immediately got to tearing it down. My wife and I were living in a RA apartment in one of the dorms at Auburn University at the time, and my wife reluctantly agreed to let me work on it in our apartment. I used the bathroom and bathtub for all my parts cleaning, sanding, and polishing work. The living room was used for tearing down the bike and making small parts. I used my parents garage a few hours away when I needed to do paint and welding. It took about a year to finish and cost me about $1500 total.

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The JIS bolts holding the engine together were a pain in the ass to get out. I had to drill half of them out. I later replaced them with stainless hex bolts.

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Auto part Engine Automotive engine part Carburetor


I dropped of the cylinder at Langcourt in Auburn and they did a great job cleaning up the bore to fit the new 0.25 over piston. It's weird that one of the top companies that does this happened to be in Auburn and it was cheaper than any other place i could find.

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I liked the bead blast they did on the cylinder, so I had them blast the rest of the engine for me too.

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Then I polished all the aluminum parts, replaced bearings and seals, and put it all back together.

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Then I rebuilt the wheels, forks, and shocks. Painted them and parkerized the spokes.

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Next I made a new wiring harness. I had to added turn signal wiring, converted it from 6v to 12v, and wire in the LED brake light I made.

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#2 ·
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I painted it with a epoxy primer and a single stage 1960s Ford Reef Aqua top coat. Then I made a seat pan and various other parts.

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Here it is partly assembles and started for the first time without the silencer on the exhaust. The original chain fractured into tiny pieces when I tried to move for the first time, so I didn't get to ride until the new chain came in. It also didn't run very well with the original carb. I added a 2004 crf80 carb, which worked perfectly with the open intake and exhaust.



Here is the license plate light. Just happened to have an LED that fit a 45 casing perfectly.

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Then I made a seat cover and knee pad covers from some nice leather. Made an exhaust with some stainless pipe, stainless water bottles, and fiber glass. Wrapped the handle bars with some leather cord. Drilled and tapped the left bar end, so I could added a Harley mirror to it. Made a license plate bracket, headlight bracket for the LED headlight, speedo bracket, and various other small parts. Here is the first moving test drive.



Finally, here are some pics of the finished bike.

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#3 ·
Very tastefully done.
 
#8 ·
I bent a 1" stainless pipe with a JD2 bender. Then rolled a piece of perforated steel sheet to make a 1" pipe that got welded to the end of the stainless pipe. The perforated pipe starts about an inch after the silencer starts. I got 2 large stainless water bottles that are about 3.5" diameter and cut the top off of one of them and the bottom off the other. Then I welded those together and stuffed them with high temp fiberglass insulation. Then I welded the silencer to the rest of the pipe. I polished up all the stainless before welding it all together. It's loud when you get on the throttle, but it doesn't sound whiny as I was expecting for a 90cc bike. It sounds pretty mean for such a small bike.

I would have preferred more of a cafe seat with a hump, but my wife wanted to be able to ride on it with me some times, so I made a bigger flat seat. It's got a few inches of foam, so its really comfortable, and I figured it was a small compromise considering how cool she was with me working on the bike in the apartment.
 
#6 ·
My wife and I were living in a RA apartment in one of the dorms at Auburn University at the time, and my wife reluctantly agreed to let me work on it in our apartment. I used the bathroom and bathtub for all my parts cleaning, sanding, and polishing work. The living room was used for tearing down the bike and making small parts.
Number......

1) I am not a fan of that type of seat but you pulled it off nicely and didn't spend all that much for a clean, nice machine.

2) You did a lot of this in your apartment and that's impressive.

3) Your wife let you clean and polish and sand the parts in your sink and bathtub? WOW.........unheard of. She's a keeper.........be good to her and take her out on a date.
 
#7 ·
Sweet little bike! What's the top speed on this beast with the .25" overbore?
I've been thinking of building a little Honda moped that my buddy has in his backyard, but if the engine was too bad
I was going to use a chinese clone with the 60's honda frame and wheels....
 
#11 ·
They are neat little in town bikes. You did a great job. I cant say I am a fan of the seat due to the fit near the front of the tank, but if its comfortable and you guys can ride two up (probably singing "little honda" all the way) then its functional.

I am hoping to have mine done by the time they finish the new divided highway that runs parallel to my highway. Traffic will diminish by at least 400% on my road. It will make this a fun commuter instead of a get killed because you cant run 80 on a two lane blacktop ride.

I have collected: ATC 90 engine for...something....I dunno...they are the same family engine kinda. New tubes, one new hub (my original was broken through the cush drive....) and pretty much enough to build the bike with xr 80 forks. I really want to swap to some sort of disc brake front end. Possibly pitbike mix and mash.
 
#12 ·
I think the 65 was the only year of alloy cylinder with cast liner? Can't really remember but still have a couple of S90's in Britain
Way back when, CB175 piston was 'THE' overbore to do, probably 30 yrs before the Chinese clones became available
 
#14 ·
Raven,

I looked into doing the disc brake front end swap as well, but I found that the only front ends that would fit without major work had mechanical disc brakes instead of hydraulic. And a lot of the guys using them were saying the mechanical discs were a very small improvement over the stock drums. I ended up getting new brake shoes and that made a huge difference in braking performance. Before the new shoes it was a little scary how weak the brakes were, now they feel fine as long as you don't brake hard more than a few times on a row.

Here is a link to all the bikes with 27mm front fork tubes: » Motorcycle fork tube diameter list Organ Donor

Hope you can get the bike up and running soon.
 
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