1968 Honda CT90

35346 Views 49 Replies 23 Participants Last post by Unkle Krusty, 5 mo ago

jacobj11

Discussion Starter · Apr 14, 2014

I bought myself a new project to get running and ride around in while I slowly rebuild the Benly. I got her off of craigslist on Friday for $240, not too bad for a CT90, I think. The engine was frozen, it took me an entirety of two and a half hours on Saturday to free the, what looked like a brand new, piston which was rusted in place in a pristine cylinder bore. Just had to hone it out and clean up the piston and it fit like brand new. Cleaned up the combustion chamber, freed the valves, and reassembled the top end to find that it has flawless compression and turns over nicely. Now I'm waiting for the PZ-19 Carb and the battery I ordered to see if I can get a pop out of her.

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Graceshredder

· #2 · Apr 14, 2014

Way cool! I love the old Trail Bikes from Honda. Nice find!

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jacobj11

Discussion Starter · #3 · Apr 14, 2014

Thanks! I can't wait to get her up and running. I've been wanting a Trail Cub for a long time, and I think I got a steal for this one!

I'm hoping this Chinese replacement carb will fit without any fuss. I would've gone for an original, but I couldn't find one for this model bike for a reasonable price. http://www.ebay.com/itm/28117061151...iewitem=&sspagename=ADME:L:OU:US:1120&vxp=mtr No altitude adjustment, and no boot to fit it, though. /:

jacobj11

Discussion Starter · #4 · Apr 17, 2014

The carb and battery came in yesterday. The carb was shipped with a broken petcock lever and a cracked flange on the petcock, so I will soon be sending it back, but I couldn't help but put it on to see if I could get the bike running. The carb seems well built, but it does not fit the K0 manifolds. The flange is the wrong size, and the carb rubs against the intake valve cover. I stole my dad's K2 intake manifold for the time being. Maybe he won't notice.

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jacobj11

Discussion Starter · #5 · Apr 17, 2014

I got a couple of pops out of her last night, but mostly backfire. The valves are adjusted perfect, the engine has good compression, and the engine is getting gas, so that leaves one thing. The timing is wrong. Not the cam timing. I double checked it. It's perfect. I could not figure out what it was for the life of me, until I was half asleep. I may or may not have installed the cam sleeve on the spark advancer incorrectly. I'm not 100% positive that's the problem, but that's the only thing I can think of. I guess we'll see about that today after work.

I hope that's the only problem.

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sludgechugger

· #6 · May 29, 2014

Oof. Good luck. Great looking bike

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sirrealism

· #7 · May 30, 2014

240$ is a steal. Did you ever get it running?

jacobj11

Discussion Starter · #8 · Jun 10, 2014

I got her running pretty good. It's just tough to start, and I need to work out some kinks. Right now I'm trying to get the headlight to work, and I'm doing a little body work on the headlight bucket and side covers.

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Unkle Krusty

· #9 · Jun 16, 2014

Ct90

One of the best bikes ever made.
An Indian friend and customer used to buy them for ( his words ) so the young bucks can chase the cows.
Good clean ones are advertised for $2,000.00 up here.
In low range they will climb most anything. I rode a trials course on one back in the 70s.
The optional rifle scabbard was a nice touch.
I would love to have one for puttering around down town. But I can get a slightly used ( ex rental ) 50cc Honda scooter for $1,200.00 later this year.
Hope you get it running okay. They bumped them up to 110 cc later on, and the Chinese copied the motor and made a cute bike too.

One last thing. This dirt bike chat is refreshing after all the pavement chat.

Unkle Crusty

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TennesseeZ

· #10 · Jun 16, 2014

Nice project!! I hope you will continue to post pics as you make progress!
Welcome from East Tennessee!
Regards
Ed

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Offcenter

· #11 · Jun 16, 2014

I have a '77 myself.
Fun bike to ride!

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hkrocker

· #12 · Jun 18, 2014

Nice....

Would love to have one of those to zip around the city. So convenient.

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jacobj11

Discussion Starter · #13 · Jun 27, 2014

hkrocker said:
Would love to have one of those to zip around the city. So convenient.

Craigslist is the best place to go, and you can sometimes get lucky asking around for people wanting to sell parts bikes. My dad was talking to a coworker and he mentioned wanting a CT90, and the guy just gave one that he had to him. You can find them nearly everywhere, especially here in the Texas Panhandle where nearly a third of the population either own farms or ranches.

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jacobj11

Discussion Starter · #14 · Jun 27, 2014

I worked out all of the kinks on her that were keeping her from running. I replaced the valve springs with dratv.com's heavy duty springs and I replaced the valves, gaskets, and oilseals along with them.

I took the old intake manifold and ground out the bolt holes so the PZ19 carburetor would at least fit, and it looks like ****, but it works. Eventually I'll cut the carb mount off and weld on a K1-76 mount on there.

I ordered some new points and a bracket, and while I waited for that I did a little bit of body work on the side covers and headlight bucket. I wanted to paint the side covers white, since that's how the side covers were stock, but I quickly learned that automotive paint doesn't like to stick to plastic. Any suggestions on that?

The points got the bike to daily riding condition, which is fantastic. I also got the title and plates for this and the Benly, which I'm rebuilding the engine on right now. I'll update about that later.

One of the last things I need to do is to get that stinking headlight working. I'm thinking some points are dirty inside of the handlebar switch, but I'm not sure. My voltometer does not read any power going to the headlight with the key on and the headlight switch in place, no matter where I put the terminals or if the headlight is plugged in or not. I figure I'd take it to the motorcycle shop here in town and have the owner look at it, but I'd like to figure it out myself. Anyone have any suggestions as to what to look for?

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Luvs2Play

· #15 · Jun 27, 2014

I found this site that has the service manuals and wiring diagrams on PDF. Might be able to point you in the right direction.

http://ct90-ct110.com/Home.html

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jacobj11

Discussion Starter · #16 · Jun 27, 2014 (Edited)

Luvs2Play said:
I found this site that has the service manuals and wiring diagrams on PDF. Might be able to point you in the right direction.

http://ct90-ct110.com/Home.html

Well...... I'll have to learn eventually. I'm off this next week, so I'll have time to do it at the lake. While I'm at it I'll see about installing the winkers. I slipped and got standard plates instead of vintage plates, so I evidently need blinkers to get it inspected.

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jacobj11

Discussion Starter · #17 · Jul 7, 2014

I had problems with the CT smoking, idling rough, fouling the spark plug, and hesitating all week. I had to adjust the jet needle all the way out to eliminate all of these problems, the timing is perfect, and she's just about a daily rider now.

The ground on the headlight was ripped off of the socket, which explains why it doesn't work, so I ordered a new one from dratv.

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Graceshredder

· #18 · Jul 8, 2014

Sweet! Nicely done.

nickonometry

· #19 · Jul 8, 2014

I had a couple of CT90s and they've always been alot of fun. $240 is super cheap IMO!

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jacobj11

Discussion Starter · #20 · Jul 11, 2014

Would anyone be willing to trade a 66-68 CT90 or CT200 carburetor for what looks to be a unused NOS K2-79 stator? We also have NOS K0 and 200 headlights, battery boxes in pretty good condition, and a few other odds and ends.

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