Noll Posted June 21, 2021 Report Share Posted June 21, 2021 (edited) I'd been wanting an old honda motorcycle for a while, so when this showed up on FB marketplace at a price I couldn't say no to I picked it up. I need another project vehicle like I need a hole in my head, but oh well lol. It's been engine-swapped with a 125cc from a honda 3-wheeler, so should have a bit more get-up-and-go than the stock 90cc. 8 hour round-trip to go get it: It had been in a barn for a while, and was filthy, so first order of business was to fix that. The reason I got this thing so cheap was that it is in need of a fair bit of work, and had some missing parts. First up was that the rear sprocket and chain were entirely missing. It took a bit for me to be able to go get the bike (darn provincial border closures), so I had ordered a new chain and used sprocket off ebay while I was waiting. Much better. A 'fun' future project is going to be dealing with all the wiring, which has just been unplugged and left dangling. These bikes are 6v and the engine in it now is 12v, so I assume this was just done to prevent blowing all the bulbs and they never got around to wiring in a 12>6v regulator or swapping the bike's stuff for 12v. As it is now the bike should be able to run; the CDI is wired up and there is spark when it's cranked even with no battery. Speaking of spark, the lead had totally had it, so I replaced with one of the ones that was on my Z when I got it, chopped down to the correct length. The plug isn't in right now because someone stripped the hole and helicoiled it bigger, but the helicoil was coming out and the (larger) threads were pretty messed up. Going to get a m14x1.25 tap and try to fix the threads and use a larger spark plug (stock thread was 12x1.25mm). Then there's this interesting setup, I guess the stock bash bar/footpeg mount didn't fit on the larger engine. I'll be making up something a lot nicer for this purpose, as well as incorporating a skidplate etc (these bikes were designed for on/offroad use after all). Some other misc. - One of the exhaust mount studs was broken off, and it was a weird combo mount with the rear shock nut. Welded something workable together: Spaced it out a bit too as how it was before it had melted the plastic shield a bit: Current goal is to get it running/driving, have some fun offroad with it, then fix the wiring, get it registered (I only have a bill of sale currently), and road legal. Oh, and I need to get a motorcycle license haha. Edited June 21, 2021 by Noll 2 Quote Link to comment
Noll Posted June 22, 2021 Author Report Share Posted June 22, 2021 Got the spark plug hole tapped to m14x1.25 with no issues happily. Verified that there is spark, there's definitely fuel getting into the engine (replaced with fresh too although the old gas looked fine), air is a given, but no start even with starting fluid, it wouldn't even pop. Some investigation into why lead to a compression test, which ended up as 30psi. Not good, very not good in fact. I'm hoping it's just stuck rings, have dumped a bunch of ATF down the spark plug hole so we'll see what that does tomorrow. The piston being almost sideways makes it a bit less effective, but here's hoping. worst-case these are dead easy and cheap to rebuild, hopefully can run it as-is though. Quote Link to comment
Noll Posted June 24, 2021 Author Report Share Posted June 24, 2021 (edited) Ok, engine pulled apart, and culprit found. I think at some point someone ran a spark plug that was too long, and it hit the intake valve before something broke off and bounced around a little. Thankfully the piston, rings, and cylinder walls both look perfectly fine. The valve seats are alright too, the exhaust valve hadn't been seating very well but that seems unrelated. Whatever hit the intake valve dented it hard enough to deform the backside. Super high-tech homemade valve spring compressor setup, and the current state of things: Also realized this engine is actually out of an ATC110, which mean an even simpler wiring diagram to deal with which is nice. The entire atc harness is stuffed into the ct90 right now, should be able to use most of it as-is with some shortening of wires. it's set up to have 2 different main alternator outputs, the black/red to the coil and CDI, and yellow to the lights. I'm sure I can work out a way to make the yellow work for both the lights as well as a voltage regulator of some sort + a battery if I decide to not just keep the battery-less setup. Undecided though, we'll see what route I take. Edited June 24, 2021 by Noll 2 Quote Link to comment
]2eDeYe Posted June 25, 2021 Report Share Posted June 25, 2021 Awesome! I learned to ride on one of these on my uncles farm. I am rebuilding an old Yamaha version of one of these that me and my brother rode as kids. 😄 1 Quote Link to comment
]2eDeYe Posted June 25, 2021 Report Share Posted June 25, 2021 There is a guy on youtube that rides one all over. He modified it with a bigger engine and an mx frontend. 1 Quote Link to comment
Noll Posted June 25, 2021 Author Report Share Posted June 25, 2021 (edited) 7 minutes ago, ]2eDeYe said: Awesome! I learned to ride on one of these on my uncles farm. I am rebuilding an old Yamaha version of one of these that me and my brother rode as kids. 😄 4 minutes ago, ]2eDeYe said: There is a guy on youtube that rides one all over. He modified it with a bigger engine and an mx frontend. Nice! They (and other similar bikes) are pretty neat, it's not going to be fast but should be a good time. Oh yeah, C90Adventures is how I found out about the c/ct bikes to begin with as it happens. Hopefully he's able to resume his trip soon, the videos are awesome. Edited June 25, 2021 by Noll 1 Quote Link to comment
]2eDeYe Posted June 25, 2021 Report Share Posted June 25, 2021 I have a couple 74 Yamaha DT 100's as well. Super slow, but fun as heck. Yeah his videos are great. 1 Quote Link to comment
Noll Posted June 26, 2021 Author Report Share Posted June 26, 2021 (edited) Ok, A bunch of looking at the engine harness and frame harness diagrams later, I'm pretty sure I've photoshopped a combined harness that will work. if I can find a dual pole (separated) keyed ignition switch I'll run the lighting/horn circuit through that so it only works with key on. I don't want to run the coil power and light power wires through the same contacts, defeats the point of them being separate and might break things. Edited June 26, 2021 by Noll 1 Quote Link to comment
Lockleaf Posted June 27, 2021 Report Share Posted June 27, 2021 If cant find a switch like you want, couldn't you use the key to trigger a relay to power up the two circuits independently? 1 Quote Link to comment
Noll Posted June 28, 2021 Author Report Share Posted June 28, 2021 (edited) 10 hours ago, Lockleaf said: If cant find a switch like you want, couldn't you use the key to trigger a relay to power up the two circuits independently? That's a good idea! I just bought a 4-wire ignition switch from a 90's honda ATV that I think SHOULD work, but that's a great backup plan if it doesn't. Should arrive tomorrow. ------------------------------- Got some stuff done on the bike today. 1st up, the exhaust had a pretty considerable split and nearby pinhole. Instead of trying to weld it up and blowing holes in the thin metal I welded a patch over everything. Next up, the foot pegs/kickstand. The setup on the bike when I got it was a bit sketchy to say the least, way heavier than it needed to be, a big catch point for rocks, tree limbs, etc and looked like stevie wonder did the welds. Made a mounting plate: Welded the (cleaned-up) pegs on, and welded a bit of square tubing between the cut-off sections. Welded some bar stock on top to give it even more strength, and cleaned stuff up. Did my best to bend the pegs int some sort of evenness as they were bent in 4 different directions, they're more even than they look here. And on the bike. Happy with how it turned out! Will get some paint of course, just need to decide if I want to integrate the skidplate I'll be making into it or have that be a separate bolt-on piece. Edited June 28, 2021 by Noll 2 Quote Link to comment
Noll Posted July 1, 2021 Author Report Share Posted July 1, 2021 (edited) Got some more done today. With the homemade wiring diagram in hand, I cleaned up the bike's harness to match, as well as adding in the ignition key switch etc. Pretty happy with the result. My bike's missing the cover that would normally hide the harness running along the tube here, but it doesn't look terrible IMO. I'll also be 3d-printing a cover for the back of the hole the ignition switch goes in. The light wiring is still left unplugged for now though, want to get the bike running first and will need to do something about the 6v headlight before I can plug any of the lights in (the headlight's load stops all the other bulbs from blowing with this battery-less system). I have an old 7" H4 light with a smashed lense lying around, I might cut the base out of that and epoxy it to the back of the 6v light (which is currently a sealed beam) to allow me to use conventional bulbs. If I can find a 35/35w H4 bulb (the same as stock for the atv the engine came out of) I see no reason this wouldn't work fine. One upside to the lack of battery with this config means that I can at some point get some wrenches etc and make a little tool roll specifically for the bike stored where the battery would have gone. Handy for when doing a road trip etc. Yesterday I went to our DMV equivalent and got the bike actually registered in my name. Despite not having ownership papers this was relatively straightforward, bill of sale from the guy I got it from and a sworn affidavit I wrote up explaining why I thought I was the rightful owner and away I went. it did take a bit of time though as they had to call head office due to the vin # being one digit shorter than the minimum their system would accept lol. I would have thought there would have been some sort of override for older pre-standardized-vin-length vehicles, but I guess not. They did something in the end that worked though, and I now have ownership paperwork in my name 🙂 . Pretty much just waiting on parts now, not sure if there's anything else I can really do in the meantime. Edited July 2, 2021 by Noll 1 Quote Link to comment
Noll Posted July 3, 2021 Author Report Share Posted July 3, 2021 Well, new tires ended up showing up today (wasn't expecting them till next week at the earliest), so got them swapped on. Was more of a hassle than it should have been, but got them done in the end with no leaks in the tubes. 2 Quote Link to comment
Noll Posted July 3, 2021 Author Report Share Posted July 3, 2021 Ignition switch hole cover made up and installed. Will do the job of stopping the switch body from wiggling around and cleans up the look a little. 2 Quote Link to comment
]2eDeYe Posted July 4, 2021 Report Share Posted July 4, 2021 3d printing is awesome. 😄 1 Quote Link to comment
Noll Posted July 4, 2021 Author Report Share Posted July 4, 2021 2 hours ago, ]2eDeYe said: 3d printing is awesome. 😄 It really is. Super nice to be able to grab some dimensions off something, do some CAD design, kick off a print, and have a completed part a few hours later. This will have some more printed parts on it as time goes on I'm sure, and the Z definitely will too in the interior etc. 1 Quote Link to comment
Noll Posted July 8, 2021 Author Report Share Posted July 8, 2021 (edited) Got a lot done the past couple of days, but didn't take many pics. Had my 2nd vaccine shot yesterday and was/am feeling like death, so was just getting stuff done as opposed to doing photos. New valves showed up yesterday, so got them all lapped and installed with springs etc. Did a water leakdown test overnight, perfect seal. Spent a few hours today putting everything back together, doing timing, valve lash, etc etc etc. Happily over 120psi (pic was before I got it up to the final value); heck of a lot better than the 30 it was at before. It fired right up with starter fluid down the intake, but there's absolutely nothing when trying to just let the carb do its thing which isn't super surprising. The bike sat for quite a while in a barn before I got it, so probably just old gas gumming things up. Will tear down the carb tomorrow if time allows, that should be the final hurdle to making it drivable. Then just need my new brake levers to show up, adjust the rear brakes, and figure out what I'm doing for a headlight (pretty sure this engine is 12v and I have a 6v sealed-beam installed at the moment). Also had a lawnmower air filter and a bunch of 1.5" radiator hose arrive, going to make my own airbox setup instead of spending 150-200+USD on used oem parts. Edited July 8, 2021 by Noll 1 Quote Link to comment
jagman Posted July 9, 2021 Report Share Posted July 9, 2021 You could probably use a mower carb for a single cyl briggs and a ram air intake. Quote Link to comment
Noll Posted July 24, 2021 Author Report Share Posted July 24, 2021 Happily the carb is there in in great working order, want to make an airbox to keep the low-pressure intake stuff and allow me to have the intake up high as it is stock for water crossings etc. ------------------------------------- Dropped off from posting in this thread for a little bit. Just after my last post I got the carb cleaned and working well, and drove the bike up and down the driveway. Pulled the plug to check how it looked, and this finished off what was lest of the threads in the head 😞 . needless to say this was a bit disheartening, but after a week or so I got the head to a machine shop that was able to put in a thread insert despite the hole having already previously been drilled/tapped larger. I then threw the engine back together for the second time, and was able to properly ride it for the first time! Oddly it runs clean when cold but was smoking a ton after it warmed up - rings/cylinder looked good, brand new valve stem seals, etc and the fact that it doesn't happen when cold is rather odd IMO. I have a hunch that a bunch of the ATF I dumped into the cylinder back when i was figuring out the cause of no compression is in the exhaust and burning off once the exhaust gets hot. Going to try to run the bike without the muffler (just the up-pipe) and see if that makes a difference, would make sense that there was atf in the miffler baffles if so. Beyond that, if anyone has suggestions as to what could cause this I'm all ears, seems like wayyyyy too much to be condensation burning off lol. The other annoying thing is that the rubber seal that's for where the chain travels between the cylinder and head is leaking a decent amount, so I get to tear the head off for the 3RD time to fix it. Whee. bit of RTV silicone applied carefully to both sides where the gasket goes and some aviation gasket sealer on the metal-to-metal mating surfaces should do the trick I hope. Didn't feel like doing more engine work just yet though, so today I worked on modifying the headlight. cut the sealed beam light assembly out and drilled the hole out larger: Bought a cheap chinese ATV headlight off amazon for ~20$ CAD or so , and hacked it up till I had just the headlight holder assembly. Epoxied that in place the right way up, and once that cures I'll have a 12v headlight with replacable bulbs instead of the stock 6v sealed beam 🙂 . 1 Quote Link to comment
Noll Posted July 25, 2021 Author Report Share Posted July 25, 2021 No major progress today, but I did run the bike for 20 minutes with no muffler, and confirmed that there is no smoke at all under any amount of throttle. Has to be ATF (or oil I guess) in the muffler baffles then, guess I just need to ride it long enough for it to burn off. Gratuitous motorcycle pic just because. 2 Quote Link to comment
Noll Posted August 1, 2021 Author Report Share Posted August 1, 2021 Bunch of welding jobs done today. First up, the exhaust was3 different bits only slip-fit together (some previous owner doing a DIY job to make the exhaust work with the ATC engine) and leaked like a sieve, so I tacked everything, removed it, and welded it up. Exhaust is still a slip-fit into the muffler but has gaskets etc there to stop it leaking. Next up, got the rear brakes working. Stock the bike would have had a foot brake pedal for the rear in addition to the hand lever, but that and the center stand are MIA. The way the linkage works, without something holding the rod that goes to the foot lever in place the brakes don't work when you use the hand brake, so I made a little tab and welded it on the frame to do so. I want to get a foot brake setup eventually, won't be hard to remove the tab and give it a lick of paint when that happens. lastly, the bike had a skidplate/bash guard from stock and that is also missing. I could buy an OEM one but they're not super beefy and I don't know if it would work with the engine swap anyway, so I started making my own. cut up some square tube and welded in some captive nuts, then welded to the footpeg mount. Don't mind the crap welds, welding upside down sucks - i'll pull it off and finish weld/paint later. Didn't want the skidplate being welded directly to the peg mount as taking it off would involve removing the side-stand and it's a pain to keep the bike upright if so. Bent up some steel rod I had lying around, and mocked up. the underside of the engine will of course get a beefy skidplate etc, not sure yet if I'll have a hole for oil drain or have the skidplate be removed for that. I'll finish that the next time I work on the bike. At this point it's skidplate, air intake box, and wait on the voltage controller to arrive and it should be ready to get made road legal! 2 Quote Link to comment
]2eDeYe Posted August 2, 2021 Report Share Posted August 2, 2021 On 7/24/2021 at 2:33 PM, Noll said: Happily the carb is there in in great working order, want to make an airbox to keep the low-pressure intake stuff and allow me to have the intake up high as it is stock for water crossings etc. ------------------------------------- Dropped off from posting in this thread for a little bit. Just after my last post I got the carb cleaned and working well, and drove the bike up and down the driveway. Pulled the plug to check how it looked, and this finished off what was lest of the threads in the head 😞 . needless to say this was a bit disheartening, but after a week or so I got the head to a machine shop that was able to put in a thread insert despite the hole having already previously been drilled/tapped larger. I then threw the engine back together for the second time, and was able to properly ride it for the first time! Oddly it runs clean when cold but was smoking a ton after it warmed up - rings/cylinder looked good, brand new valve stem seals, etc and the fact that it doesn't happen when cold is rather odd IMO. I have a hunch that a bunch of the ATF I dumped into the cylinder back when i was figuring out the cause of no compression is in the exhaust and burning off once the exhaust gets hot. Going to try to run the bike without the muffler (just the up-pipe) and see if that makes a difference, would make sense that there was atf in the miffler baffles if so. Beyond that, if anyone has suggestions as to what could cause this I'm all ears, seems like wayyyyy too much to be condensation burning off lol. The other annoying thing is that the rubber seal that's for where the chain travels between the cylinder and head is leaking a decent amount, so I get to tear the head off for the 3RD time to fix it. Whee. bit of RTV silicone applied carefully to both sides where the gasket goes and some aviation gasket sealer on the metal-to-metal mating surfaces should do the trick I hope. Didn't feel like doing more engine work just yet though, so today I worked on modifying the headlight. cut the sealed beam light assembly out and drilled the hole out larger: Bought a cheap chinese ATV headlight off amazon for ~20$ CAD or so , and hacked it up till I had just the headlight holder assembly. Epoxied that in place the right way up, and once that cures I'll have a 12v headlight with replacable bulbs instead of the stock 6v sealed beam 🙂 . Great simple mod. 🙂 1 Quote Link to comment
Noll Posted August 2, 2021 Author Report Share Posted August 2, 2021 19 hours ago, ]2eDeYe said: Great simple mod. 🙂 Thanks! Cheaper than buying an aftermarket headlight, and a lot faster than waiting on shipping from thailand etc 🙂 . -------------------------- Got the skidplate all built and painted today, pretty happy with how it turned out. 4mm steel plate and solid rod, so it should be able to take quite the hit without bending. 2 Quote Link to comment
]2eDeYe Posted August 2, 2021 Report Share Posted August 2, 2021 It'll look great with some scratches on it. 1 Quote Link to comment
Noll Posted August 3, 2021 Author Report Share Posted August 3, 2021 23 hours ago, ]2eDeYe said: It'll look great with some scratches on it. Will definitely match the rest of the bike's paint better that way lol. Had another test ride today, pretty sure i burned out the last of the ATF in the exhaust finally and also scuffeds the skidplate slightly lol. The voltage regulator (silver box below the cdi) arrived so got that wired up - nothing to it really, one to ground and one to the main power lead for the lights. It's set to max out at 13.7 or .8 volts stock, but I could adjust it higher or lower if I want. side mirrors arrived too, so got them on. This thing is looking pretty good if I do say so myself! All that's left now is to make an airbox, and then it can go get safety'd . 2 Quote Link to comment
Noll Posted December 23, 2021 Author Report Share Posted December 23, 2021 Haven't updated this thread in a while, but have been tinkering away on the bike. Rewired all of the brake light circuit so it all works, did a LED headlight conversion, and purchased a CT200 (the bike before the ct90) center stand and boot brake pedal and modified it to work on the 90 (the 200 assembly was FAR cheaper on ebay than 90 specific stuff and it only required me to lengthen the legs of the stand and some other misc.). Finally got around to pulling the head off again the other day to diagnose/fix the oil leak that the bike has had for a while now. Can you spot the issue lol? [/url] Somehow the headgasket dropped down a bit last time the head was installed, whoops. These CTs are unkillable though, other than the oil leak (HG sandwiched between head and barrel let oil leak from the chain passage) the bike ran perfectly, started first time, etc. if it wasn't for the oil leak I'd never have pulled it apart. Happily i had a new one from the gasket set I ordered when I pulled the head off the first time. I didn't use it then as the OD was slightly too large for some reason, but 5 minutes with a file and scotchbrite pad on the copper gasket fixed that right up. While it was off, I added a horizontal brace piece to the tube uprights of the skidplate, should make it more resilient to smacking something from below and then bending these outwards. And with that it's pretty much ready to go get a safety inspection and license plates whenever I get around to that (probably spring). Rolled it outside this evening to have a look at the effectiveness of the LED headlight: 2 Quote Link to comment
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