Honda CT90 Engine Rebuild Questions

[nnnnnate]

I've got a 1969 CT90 that has been in my dads family forever. One of my few childhood memories is of riding on it with my uncle up at Brighton. We got cutoff or something and ended up tipping over on the exhaust side and I burned the snot out of me leg. Despite that, I love the little bike.

Anyway, it was showing signs of low compression and was having trouble shifting last time it ran. In 2011 I decided I was going to rip it apart and rebuild it to its former glory. I pulled the engine and took it all apart. This was a mistake. It got cold in the garage and I stopped working on it and it has sat since then. I've got a little more time and a little more money now and want to get it put back together. One of my neighbors like to dirt bike and said he would help me get it back together but I'm now thinking I might just like to pay someone to get the motor rebuilt and working.

I plan to ask my friend (neighbor) first if he is interested in doing the work but hoped to get an idea of what I should pay him for it. Right now both of the covers are off, I'd like someone to look at the transmission to see if anything there is broken or needs replacing. I have all new gaskets, a new piston and rings (although I'm not sure if they are correct, I just ordered stock stuff from dratv.com). I'm 99% sure I have all the parts needed, I just don't have the skills or patience or knowledge to do it myself.

Thoughts? If he isn't interested where in the valley would do work like this?

I thought I had pics saved to the cloud but now I can't find them. I'll add some this afternoon if that would help.

Thanks.

 

[Gravy]

shoot me some pics. I could likely do it.

 

[nnnnnate]

Overall I think its in pretty good shape.



This is how it stands right now.



I have all the misc parts that I have pulled off the engine in bags that are organized pretty well. I tried to take things apart methodically and keep components more or less together. I labeled the bags as well to help me get it back together.

I bought a whole set of new gaskets, a new carb, and new piston and rings. Although the head is on the engine its not bolted together and I'd like it to be taken back apart to ensure that its put together correctly.



Anything I'm missing?

 

[Gravy]

Looks like it's all there. You might pressure test the intake and exhaust valves to see if they leak. A rubber cork works well for this.
Low compression on these sometimes comes from carbon deposits on or worn valve seats, but almost always the valve rocker gap need to be adjusted. If they are too tight you'll get no compression.

Make sure you gap the rings. I don't think they always come pre-gapped

 

[nnnnnate]

So I'm going to bump this thread.

I was actually able to get this thing running back in 2015 but it was leaking a bunch of gas and I thought the issue was the carb (which is an oddball '69) so I never did anything with it after putting it back together and getting it to run.

So, fast forward 5 years and I moved and the 90 has been parked at my parents for 2+ years. My neighbors kid has one of those Coleman 200 tote goat things and is always out on it messing around. I hopped on it Monday night and told my son to grab his new bike helmet and I took him up the street and back on it. He loved it and told me later that night that "we need to do more rides like that daddy." That got me thinking that I needed to get the ct90 and take it to another neighbor that has a kid who is pretty handy with motorcycles and was willing to fiddle with it.

I took it over yesterday and he fired it pretty much right up after it sat for 5 years and it immediately started leaking fuel. We ended up stripping it down so we could replace the fuel lines and he took apart the carb while I was buying more the hose. After swapping the hose and spraying a bunch of carb cleaner through it he put it back together and fired it back up and......it didn't leak. It was past my bedtime at that point (10pm) so we called it and he said he'd button it back up today and give me a ring. He said he also wanted to adjust the valve clearance too.

I went over about 9 tonight and it was all set. I took it for a rip up the street and was cycling through the gears when the next one didn't do anything at all. I coasted back thinking there was an issue with the sub transmission or something else and he saw that I blew the chain. It was running really well before that blew and I was grinning ear to ear.

First priority tomorrow at lunch is to procure a new one then get it installed so I can take eli for a ride.

 

[johngottfredson]

That’s awesome! As an aside, with that covid-stache, you might consider letting the neighborhood know that the kid riding around with you on your scooter is your actual child. Avoid some headaches later on.

 

[nnnnnate]

So the neighbor kid that helped (temp. home from mission in Philippines) had a tool tote full of HF tools. Hes got a z50 that was his moms growing up and he swapped in a 125cc motor in it after rebuilding the OE one a few times. They also have a taotao dirt bike but I think hes got a "real" one too.

Are the big name dirt bikes all metric? I was thinking that maybe I'd buy him a tool or set as a thank you for helping me get this sorted out. I'd be happy to take suggestions on tools for someone in his position with functional but not great tools. I was thinking maybe something like this but they don't have any in stock. (+/- $100 range.)

 

[Tonkaman]

Yes motorcycles stuff is all metric.

A set of T-handles is a great gift

Torx and Allen heads are a great addition as well.

Tusk Deep Socket T-Handle Wrench Set | Parts & Accessories | Rocky Mountain ATV/MC

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[nnnnnate]

I got the new chain on and took my boy for a 30+ minute tour of the neighborhood and we were both in heaven. It was really cool to drive around on something I knew had been in the family so long. I'm planning to take it to some family camp trips and share the love.

 

[nnnnnate]

As an aside, I zipped back over to the neighbors house and found the kid was working on his z50. He had broken the motor a bunch of times and ended up buying and installing a 125 cc motor he bought off eBay. They had just finished installing an electric start when I got over and fired it up. It was pretty crazy and was super loud. He was popping the front end up on each shift...



Have any of you guys watched carsandcameras on YouTube? They do mini bike and go cart videos that I've been binging all week. They've got me convinced that I need to build a 2 seater go cart.

 

[johngottfredson]

I got the new chain on and took my boy for a 30+ minute tour of the neighborhood and we were both in heaven. It was really cool to drive around on something I knew had been in the family so long. I'm planning to take it to some family camp trips and share the love.View attachment 127956

Man, that takes me back. My first bike was a trail 90. I gave it away when I got home from my mission...had no idea they were so valuable, or that I would be kicking myself for eternity! Love that you’re able to rock the family heritage bike with your boy. So cool.