Restoring Dads CT70 KO

Discussion in 'Projects/Builds' started by Atomic Rebel, Dec 19, 2019.

  1. Atomic Rebel

    Atomic Rebel New Member

    Joined:
    Dec 19, 2019
    Messages:
    9
    Likes Received:
    3
    Hello! I've been reading this forum a lot lately and have a bunch of questions regarding the CT70 I'm working on. So, I figured I would make a post of my own.

    Perhaps we had better start at the beginning! My dad has had a CT70 stored in the barn for as long as I can remember. Frame number CT70-143244, which I believe to be a KO, correct? The license plate has a sticker from 1988, so I imagine it's been sitting in the barn for roughly 30 years. Growing up, I always wanted to get it running with my dad, but we never got around to it. So after getting addicted to motorcycles over the past 4 years, I've now decided to take it upon myself to get it running and potentially do some cosmetic restorations. Once I get the engine running, I want to surprise my dad with it and include him on the rest of the project. I'm fairly new to working on engine internals, but I know my way around a wrench and have a good concept of the mechanical parts to an engine.

    OK, now on to the bike itself. Specifically the motor. The carburetor was removed a couple years back, and the intake had since filled up with dirt and debris. Not a good start to the project. I took off the head and the cylinder and cleaned them up a little bit to inspect them. In the first picture, you can see the cylinder has some rust. Can this be honed out with one of those 3 piece hones that go in a drill? Or will the cylinder need to be bored out the next size bigger? Next up is the cylinder head. One of the valves was stuck when I removed the head, and I had to tap it out. After cleaning out the valve guides with a brass brush and cleaning all the gunk off the valves, I tried to reinsert the valves into the head to see if everything was freed up. The exhaust valve slides in fine, but the intake valve gets stuck and won't go in. I was planning on buying new valves since the old ones have a couple imperfections around the sealing surface. Do I need to send the head to a shop to cut the valve seat to match up with the new valves? I'm planning on buying a new piston because I'm having a heck of a time removing the old rusted on rings.The crankshaft and rod have some small surface rust on them. Is that a cause for alarm?

    The odometer says it only has 4,387 miles, so I really don't expect much to need replaced inside the case. I'm going to split it anyways though because there is gunky oil inside that I want to wipe clean. That brings me to my next question. I'm having a heck of a time getting the old gaskets removed from the engine! Does anyone have any tips to help remove the gaskets without scratching the mating surfaces?

    As far as parts go, where does everyone buy from? I want to stay away from the cheap Chinese junk out there, but I obviously don't want to spend a fortune on this project either. I'm looking for recommendations on a gasket set too. I've looked at CHP and MyTrailBuddy for some parts but was wondering where everyone else orders from.

    Thanks so much in advance!
     

    Attached Files:

  2.  
  3. racerx

    racerx Administrator
    Staff Member Administrator

    Joined:
    Jul 10, 2005
    Messages:
    14,726
    Likes Received:
    1,663
    Welcome aboard!:)

    Looks like a machine that has "good bones", i.e. a solid basis for a restoration, or just building something nice. Judging by your pix, most of the resources will go toward body/paintwork & chrome. I see lots of surface rust; it's fugly more than anything else. But, with a restoration, cosmetics matter, a lot. Fortunately, straight parts are easier to restore than damaged, or missing, parts.

    You're right, 4K isn't a lot of miles. Unfortunately, it's more than enough to result in worn lower end parts, when not properly maintained & stored. Back in the day, few owners changed oil on a timely basis...and virtually no one ever cleaned an oil spinner. Judging by the scoring/scuffing on the piston, there's a lot of dirt that circulated throughout this engine. The rust seen in the bore is likely going to mean going first oversize, at a minimum, to reach uniformly clean, virgin, metal...needed to allow proper ring sealing. The head really doesn't look bad. The intake valve is pretty worn, the contact band is ~3X as wide as it should be; I've seen far worse. The sticky valve is a major concern. That said, the valve guides will probably be okay with just a honing. New valves are readily available and there looks to be plenty of material to do more than one valve job. Absolute worst case, the valve guides are D.O.A....new guides are cheap and available. I would split the cases, looking for worn shift forks (very likely, with a K0), sludge, and...possibly...excessive connecting rod wear. Shift forks & pins are available, new, and Honda upgraded the design many years ago. The connecting rod needs to be checked for side clearance, radial play (at the big end) and the small end needs to be checked for wrist pin clearance. That's pretty much all of the "heavy" mechanicals...valve job, bore/hone/new piston & rings, timing chain assembly, clutch discs, tranny bearings, points & condenser. The rest is cosmetic. Rebuilding an engine is about 70% cleaning work. There are a few quirks with these little engines. Take your time, if you can't figure something out, slow down and treat the problem as a separate issue...that's part of the learning curve. Some extra time, care and research should carry you through...and you'll acquire some expertise along the way. When in doubt, ask questions. You know where to ask them...
     
  4. Atomic Rebel

    Atomic Rebel New Member

    Joined:
    Dec 19, 2019
    Messages:
    9
    Likes Received:
    3
    Thanks for the reply! I'm waiting on some tools to pull the flywheel and the clutch, and then I'll be splitting the case to check everything out and clean up the sludge. I plan on tearing down the clutch and replacing springs and disks while i'm in there. I'm having trouble removing the tapered screws on the clutch. I read that you can remove the 4 outer screws and the ring behind the clutch, and pop off the outer clutch case. From there you can back out the tapered screws from behind. Is that possible?

    What gasket set do you recommend when I finally start putting everything back together? Are the cheap $15-20 sets worth anything, or is there a higher quality set out there that I'm not finding?
     
  5. Tripod

    Tripod Active Member

    Joined:
    Jun 23, 2013
    Messages:
    678
    Likes Received:
    39
    Its recommended that you get some JIS screwdrivers as well as bits. Put the bits in the impact screwdriver and whack it a few times to get the frozen tapered screws loose.

    For the clutch locknut id recommend a combo 20/24mm clutch nut socket.

    You cant go wrong with oem gaskets.

    Oh and it looks like the exhaust gasket is stuck inside your cylinder head.
     
  6. kirrbby

    kirrbby Well-Known Member

    Joined:
    May 28, 2009
    Messages:
    9,632
    Likes Received:
    1,411
    Cheap gaskets work. Vesrah are very good. Genuine Honda are likely the best. Gaskets from tbparts or DrATV are very good too.

    A single edge razor blade is the best tool for scraping/slicing off old gaskets. Do yourself a couple favors...
    Buy 5 or 10 blades.
    And, remove the dowels that'll be sticking out of the gasket surfaces before you start scraping gaskets off. A large sharpening stone with lots of water is great to remove the last bits of gasket. Just go slow and sure, when you're using the stone.
    Use a tapered punch, or nail set, or even a drill bit to put into the dowels so you can grab them with channellocks if they're stubborn coming out. The punch will keep the dowels from getting misshapen by the pliers.
    Partzilla is a great place to find oem Honda parts, and parts fiches to help with assembly.
    You can buy many parts right from Honda still. But if you buy from a good vendor...tbparts, DrATV, chp, nevc, and a few others, the Chinese parts that they sell are good quality for the most part. Some stuff is just nla from Honda.

    Ask all the questions you want here on lilHonda...we love to help.
     
    #5 kirrbby, Dec 21, 2019
    Last edited: Dec 21, 2019
    racerx likes this.
  7. kirrbby

    kirrbby Well-Known Member

    Joined:
    May 28, 2009
    Messages:
    9,632
    Likes Received:
    1,411
  8. Jmunk

    Jmunk Member

    Joined:
    Jul 24, 2015
    Messages:
    145
    Likes Received:
    21
    Solid project to start with. Take what Racerx says as the gospel. He, along with many others are a great wealth of information. Racerx freshened up a head for me and it was top notch!
     
  9. Gary

    Gary Well-Known Member

    Joined:
    Jan 17, 2006
    Messages:
    1,156
    Likes Received:
    207
  10. Atomic Rebel

    Atomic Rebel New Member

    Joined:
    Dec 19, 2019
    Messages:
    9
    Likes Received:
    3
    Thanks everyone for the input! I have the case split apart and am getting ready to do a deep clean of everything. Last night I used some burgundy Scotch-Brite pads and removed the majority of the old case gasket. I need to pull the alignment dowels out before I can finish up. I sent my cylinder off to a local shop and am waiting to hear back on it before I order a new piston. I got pictures back of the cylinder head from racerx, and it looks amazing!

    I took a look at the shift forks last night, and they look a little worn down, so I'll order the updated shift forks to replace them while I'm inside the case. Should I replace all the transmission bearings while I'm in there or can they just be cleaned? They don't look terrible.

    Do I need to tear down the transmission and inspect anything, or can I just clean the gears up as they are and inspect them? If I tear it down, I know I'll need to replace all the snap rings, but I'd rather not have tear it down buy replacements snap rings if I don't really need to tear down the gears.

    What do you guys use to clean up the case and the internal parts? I was planning on using a solution of simple green and water to scrub the aluminum case clean. Should I use a solvent for the gears and other non-aluminum parts? Or is simple green and water OK if I then put a little oil on everything afterwards. I don't want anything to rust while it's sitting outside the engine waiting to be put back together.
     

    Attached Files:

  11. racerx

    racerx Administrator
    Staff Member Administrator

    Joined:
    Jul 10, 2005
    Messages:
    14,726
    Likes Received:
    1,663
    The shift fork pins should be smooth, with a single diameter from top-to-bottom. If you see any bands, or "steps", they're worn...replace them with the forks. Those forks have just reached the end of their useful service lives.

    As for cleaning, heat does a great job softening old greasy dirt & sludge, also makes gasket remains less stubborn. Follow that with brushes and paper towel. Next step, parts washer. I use an old-school parts washer...mineral spirits and a flow-through brush. That'll get most of the oil & sludge. That can be followed with a little brakleen and compressed air. After that, you can work on any deep stains/oxidation using sodium hydroxide, concentrated PineSol, or aluminum cleaner...depending upon what the situation calls for. Don't worry, you'll learn what that means...by what's left behind each stage of cleaning & scrubbing. A stiff, nylon bristle brush is a good scrubbing aid and won't mar the aluminum.
     
  12. kirrbby

    kirrbby Well-Known Member

    Joined:
    May 28, 2009
    Messages:
    9,632
    Likes Received:
    1,411
    The correct answer is, you should disassemble the transmission and inspect every gear thoroughly with a magnifying glass or jewelers lens. Then replace anything that has a smidge of rust or wear.
    The other answer is, I never do all of that. I look it all over good, make sure everything spins and slides well, and pop it back in. Watch for wear on the parts that engage between gears. The "dogs" as they're sometimes called...where 2nd gear engages 3rd on the same shaft.

    For cleaning, mineral spirits, or kerosene work well, even when everything is cold. If you can heat a water base soap or solution, and KEEP it hot, that would work well too. As racerx said, if you have access to a heated parts washer...that is the shix for cleaning out greasy grime.

    Of of my favorite tools for getting into the recesses is a acid brush, with the bristles cut short. Makes the brush stiffer, and gets into the small spaces.

    IMG_20200120_140448992.jpg
     
    racerx likes this.
  13. Atomic Rebel

    Atomic Rebel New Member

    Joined:
    Dec 19, 2019
    Messages:
    9
    Likes Received:
    3
    I cleaned the case halves the best I could with some simple green and water. It's amazing how well they cleaned up! I'm going to take them into the parts cleaner at work this Saturday and get the hard to reach nooks and crannies with the mineral spirits and flow through brush. That worked really well on a dirt bike engine head I recently cleaned up.

    I visually inspected the transmission without tearing anything down, and I've determined it all looks good. So I'm going to order some new shift forks and transmission bearings and call that part good.

    The crank has a bit of surface rust in a couple places, nothing too deep at all. I wanted your guys opinions on it, but I've pretty much decided I'm not going to replace it. It's not ideal and perfect, but it should work fine, right?

    Without actually checking anything, I assume I'm going to have to replace some parts on the magneto. It looks like repair kits are hard to find right now, so I was just going to order a new condenser, points, and the felt piece. The wire winding's don't look too bad other than a little bit of rust on one side of one. What do you guys think?
     

    Attached Files:

  14. racerx

    racerx Administrator
    Staff Member Administrator

    Joined:
    Jul 10, 2005
    Messages:
    14,726
    Likes Received:
    1,663
    If you're checked rod clearances, at both ends and bearing clearance (radial) then some elbow grease applied via wire brush and mineral spirits (to keep the iron oxide dust down) should clean the surface rust adequately.
     
  15. Atomic Rebel

    Atomic Rebel New Member

    Joined:
    Dec 19, 2019
    Messages:
    9
    Likes Received:
    3
    Well, I have my engine reassembled and mounted back on the bike! Now for the part that has me worried the most about this project... Seeing if the engine will run!

    When I turn the key to the first position and give the engine a kick with the spark plug pressed against the cylinder head, I'm unable to detect any spark. The horn honks with the key turned though, so that's a good sign! When I turn the key to the second position, I don't have any lights, no spark in the plug, and the horn will no longer sound. I removed the tail light bulb and got a 6v reading from one of the contacts though.

    What would be the first things you would check out? I believe I have my points set properly, so I'm guessing either a wire has come loose somewhere or the ignition coil is bad. I have a multi-meter handy, I'm just unsure of what tests I actually need to run to check ignition.

    Thanks everyone!
     
  16. Jmunk

    Jmunk Member

    Joined:
    Jul 24, 2015
    Messages:
    145
    Likes Received:
    21
    Did you have the battery plugged in while you were kicking it over? It’s doesn’t need battery power to spark but needs the jumper wire in the battery plug connected to make spark.
     
  17. Atomic Rebel

    Atomic Rebel New Member

    Joined:
    Dec 19, 2019
    Messages:
    9
    Likes Received:
    3
    Yep, I had the jumper wire in place while trying to start it.

    I also tried to totally bypass the wiring harness and ignition by running a jumper from the magneto (black wire in harness) to the small black wire on the ignition coil. Nothing. I spent a couple hours in the garage last night checking things over and reading the forum, trying to come up with ANY reason why I wasn't getting a spark. I did managed to get a spark once... and then it was back to no spark without me even touching anything! And let me tell you, the false hope that gave me was way worse than the no hope I had before it sparked!

    I'm almost convinced my problem lies within the Magneto. I replaced the coils, condenser, and points when I rebuilt my engine, and as far as I know I have the points set properly. I hooked up a test light to the black wire in the magneto harness and to the positive battery terminal, and ran a wire from the negative terminal to ground on the bike (engine mount bolt). I then rotated the engine counterclockwise, and set the points to just start to open (test light shuts off) when the F mark on the flywheel matches up with the notch. So I think either I wired the magneto up wrong, I have a short somewhere that I can't see, or I have a defective condenser or points.

    I read that the upper right coil runs the headlights and the lower left coil runs the ignition. So I brushed the green wire against ground and kicked over the engine, and I got sparks. So I believe that coil is working properly.

    I've attached some photos to get a more experienced view on whether or not I have it wired up correctly.
     

    Attached Files:

  18. kirrbby

    kirrbby Well-Known Member

    Joined:
    May 28, 2009
    Messages:
    9,632
    Likes Received:
    1,411
    Does your ignition coil have a solid ground? Clean and tight metal to metal connection to the frame...motor to frame too...continuity between the engine case and the frame/mount on the coil??
     
  19. Atomic Rebel

    Atomic Rebel New Member

    Joined:
    Dec 19, 2019
    Messages:
    9
    Likes Received:
    3
    yes, I unplugged the black coil wire from the harness and tested the resistance from that wire to the engine mount bolt (1.8ohms), and then again from the engine mount bolt to the spark plug boot (238kohms) and once more with the spark plug boot removed (11.38kohms). So the ignition coil appears to be grounded properly.
     
  20. racerx

    racerx Administrator
    Staff Member Administrator

    Joined:
    Jul 10, 2005
    Messages:
    14,726
    Likes Received:
    1,663
    HT coil is fine. Going by the photos, the primary should be as well. This all looks like very meticulous work. First thought goes toward cleaning the points...and that's still worth trying, as newer sets seem to be coated with antioxidant. That said, the way you're getting spark, at least intermittently, points (pun NOT intended) elsewhere. Best guess is one of the leads associated with the primary is shorting-out to ground; I've highlighted the most obvious locations to check in your photo. The only other item I can think of, at the moment, is the condenser. The solder joint appears very well flowed-out...meaning a slight chance that the condenser was overheated.

    Screenshot_2020-03-24 Restoring Dads CT70 KO.png
     
  21. Atomic Rebel

    Atomic Rebel New Member

    Joined:
    Dec 19, 2019
    Messages:
    9
    Likes Received:
    3
    Well, I've come to the conclusion that it has to be the condenser. I probably overheated it with my gob of a job soldering skills! Here's the good news though, I put the old coils, points, and condenser back on the engine just for fun, and wouldn't you know.... I kicked the engine over and it sparked perfectly! So I got the carburetor and air cleaner bolted back on, poured some gas in the tank, and after two kicks it sputtered a little but didn't take off. At this point I had the biggest grin on my face. All I could think about was getting the bike fully fixed up and seeing my dads face when I ride it over to his house. So I adjusted the choke, kicked it over two more times, and it took off running! I'm sure my neighbors thought I was insane with all the maniacal laughter coming out of the garage! What a euphoric experience!

    I want to thank all of you for the help in getting this engine torn down, cleaned, and restored. I appreciate it all so much!

    Now I begin Phase II: Getting this Honda to move!
     
    allenp42, racerx and red69 like this.

Share This Page