CT70 build from box of parts

Discussion in 'Projects/Builds' started by Rakillia, Aug 25, 2018.

  1. Rakillia

    Rakillia New Member

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    Hello Forum,
    I'm Mike from NJ. I recently acquired a CT70K1. When I got it was a roller and everything else in boxes. So far I put the handlebars (which I now see are bent) on, new tires, new brake shoes, new wheel bearings, sandblasted/painted seat pan and recovered the seat. The engine had a cracked head so I figured add a new piston and cylinder while replacing the head. Couldn't salvage much from the old head so its all new now. I'm not planning on splitting the case. Based on the wear I'm seeing, this engine has some miles on it. Right now I'd just like to hear the thing run. I'm sure I'll have a lot of questions since everything not in the picture is in a box. I am very familiar with mid 80's Honda bikes and have done many resto builds over the years but this is my 1st CT70. I'm not going to be able to plate it but no one is going to bother me riding it around my lake community. Hope to get this going before the cold comes.

    IMG_4633.JPG IMG_4635.JPG
     
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  3. OLD CT

    OLD CT Well-Known Member

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    Hi Mike, Nice project. You have a K0 not a K1.
     
  4. Rakillia

    Rakillia New Member

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    I was just going off the tags. The frame says CT70-201321. The engine says CT70E-200879. From what I found, if it starts with a 2 it's a k1. I have no history on this bike
     
  5. racerx

    racerx Administrator
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    K1 production began 09/71 and K1 VINs have seven digits, whereas K0s have six.

    Nice looking roller. You should post some pix of the head. I have the sneaking suspicion that you're mistaking the "missing piece" just outside the exhaust port, at the bottom, as damage, when it's not. This is a common misunderstanding...as in "rite of passage" for every new CT70 owner.
     
  6. Rakillia

    Rakillia New Member

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    So it’s the last of the k0’s? As long as the parts I’m ordering are the same for both it’s nbd. You are correct that the crack was right at the exhaust port but it was most of the left side. It broke flush with the gasket surface. I probably could of gotten away with it but looking at the deep grooves in the rocker arms and the oblong cylinder I thought best to just replace. I’m fairly certain it happened while the engine was out of the bike. The P.O. spent all their effort on paint and cosmetics. Which is fine by me. I wouldn’t be capable of pulling off that paint job.
     
  7. racerx

    racerx Administrator
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    VINs for the K0 model topped out in the 28xxxx range, making your a late-middle-production specimen. Yes, K0 parts is K0 parts. Here's what a typical head casting looks like, completely intact.


    DSC04032.JPG

    Going by the posted you posted, I was thinking that the piston didn't look too bad...no visible scoring on the skirt. However, if you've found grooves worn into the rockers arms (would be helpful seeing some photos showing that) and an obviously tapered bore, please take some additional...if unsolicited...advice. Go deeper into this motor. The kind of wear you've described all but guarantees that there are lower end items desperately in need of attention.

    At the absolute, bare, minimum, the clutch should be rebuilt and thoroughly cleaned. The oil spinner is the inside of its front face, behind the throwout bearing flange. You'll likely find sludge...and grit...inside the crankcase; you don't want that going to work on your fresh top end. The timing chain, roller, idler & tensioner piston cap should be replaced. If either the oil pump sprocket or cam sprocket show wear, those should be replaced also. A worn oil pump sprocket usually means that the oil pump had been binding...it should be opened & inspected...replaced if the gerotor assembly is scored.

    I'd expect to find worn out shift forks, that's pretty common with the early motors. Honda improved the shift fork design and that version long-ago superseded the first type. Having the cases apart makes cleaning a whole lot more effective, easier too.

    IMHO, you've got the start of a first-rate restoration. Trying to shortcut the engine work, you're doing yourself a disservice. Better to spend an extra day and a C-note to do it right...and reap the rewards when you don't have engine problems that require going back in, after a lot of frustration(s).
     
  8. Rakillia

    Rakillia New Member

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    This is exactly why I joined the forum. Thank you. I have no problem splitting the cases or spending money. I have very little in it right now and I know they can sell for good money. Not that I have any intention of selling but I always go into these builds with the mindset that I will. My time is a little divided right now as I’m finishing up another project that’s taken 2 years so far. A 77 Ford F-150
    I rebuilt the engine,transmission and transfer case, by myself in the my garage. So in comparison, this bike will be a vacation. I’ll take more pictures when I get home. Wasn’t sure what kind of interest there would be
     
  9. racerx

    racerx Administrator
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    It sometimes takes a little time to figure out where a new owner/member is coming from. The last thing anyone wants to do is immediately jump into the deep end and risk giving an overwhelming response. Some folks have a lot of experience and a far-ranging skill set, others almost none at all; obviously, most members will fall somewhere in between those extremes. And, of course, not every owner has the same project goals.

    You should be fine going through this motor. Be forewarned, it does have its own set of quirks. A V8, it ain't. You'll need a few specialized tools: spanner socket for the clutch nut, hammer-driven impact screwdriver + JIS bits and snapring pliers. Without those, life will be a lot more difficult than it has to be. Take some time to familiarize yourself with how the tranny is assembled, R&Rd, what worn shift forks & pins look like and how to evaluate the crankshaft assembly. The rest is pretty straightforward for anyone with a modicum of mechanical skills.

    BTW, I am guessing that the original cylinder head is rebuildable, that's why I asked you to post some pix. If nothing else, you should probably keep it as the bike will be worth more if it's included, come resale time.
     
  10. Rakillia

    Rakillia New Member

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    I have most of the tools you mentioned. Hand impact is a must for old carbs. I do not nor will I probably ever own jis screwdrivers. Never needed them. I’ve restored an 85 CB450, 85 CB650 and my current bike is an 84 CB700s. Though this engine is more similar to the single cylinder, semi auto atvs I’ve worked on. Never did a clutch on them but as long as it in the Honda or clymers manual I’m not concerned.

    Some pics of the head. Like I said I probably could have gotten away with but the cost of rebuild vs just getting a new head on dratv was not a big difference. I don’t know what the green stuff is or what it’s hiding
    image.jpg image.jpg image.jpg
     
  11. OLD CT

    OLD CT Well-Known Member

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    Nothing wrong with the head and the green stuff is a factory applied paint. No big deal. Save it like racerx said.
     
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  12. racerx

    racerx Administrator
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    Nailed it, dead bang.

    Methinks that original head will be an easy rebuild & restoration project...some day. Honda castings are very good, in ways that matter. The aftermarket head will probably work just fine for you, too.
     
  13. OLD CT

    OLD CT Well-Known Member

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    Mike, I am in North Jersey BTW.
     
  14. Rakillia

    Rakillia New Member

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    I stand corrected and totally jinxed myself. I'm buying jis drivers now. I've been doing this for years and have never had much trouble. Usually swapped them for hex or Allen anyways. Until I met these 3 flat heads on the clutch.

    IMG_1072.JPG

    You can only see 1 the pic but I'm not doing that again. After I got it off and found I don't have that kind of socket I'm going to pause on the engine for a moment and rebuild the forks. I don't have that kind of puller either for the flywheel. Was tempted to use a 3 arm but that aluminum looks brittle.

    Im in Sussex county
     

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  15. OLD CT

    OLD CT Well-Known Member

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    If you have a mini torch heat each screw for a minute and try again, one at a time. The flywheel tool has left hand threads when you buy one, and go to use it.
     
  16. Rakillia

    Rakillia New Member

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    1BE785F5-6BB9-4CC7-A44C-13DC162CD6B0.jpeg So this is a fork design I’m not familiar with. I was getting conflicting info as to whether or not it had oil in it. I even bought an oil seal but alas that’s was when I thought I had a k1. The bike came with new (white plastic) guides. Looks newly greased. Not sure if I need to do anything here
     
  17. Rakillia

    Rakillia New Member

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    So i took the fork inards apart. Is this collar that the roll pin goes through, is the plastic supposed to be split? Seems it’s to small to fit without the split
     

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  18. racerx

    racerx Administrator
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    Those upper piston slides are toast. Replace `em, they're cheap.
     
  19. Rakillia

    Rakillia New Member

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    I’m trying to come up with a bulk order since the partzilla shipping is starting to add up. I’m getting the fork guides and the oil seals. The clutch pack,crank bearings. That bearing that sits outside the clutch. Points condenser if available. I’ll hold off on the coil for now. I already have everything for the top end and a carb rebuild. Are there bearings or anything in the swing arm? What size spanner do I need for the clutch? I’d rather buy a set to have it.
     
  20. racerx

    racerx Administrator
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    Unless you know how to R&R crank bearings and have the proper tool, leave them alone unless there's a damned good reason to change them. Crank (main) bearings rarely fail. The condition of the crankshaft, and the rod, at both ends, is far more important and likely to need attention. Check side clearance at the big end of the rod. Anything more than ~0.018" is likely to rattle. Any radial clearance that can be felt by hand is a bad sign. Lastly, check the small end of the rod by inserting the wrist pin than checking for fitment. It should be on the snug side, no discernible rocking. If the rod fails any of those checks, the crank should be rebuilt, or replaced.

    Dratv has all the parts you're looking for, including the clutch socket. That's the only spanner nut on the entire engine.

    Swingarm bearings are actually steel shell/rubber insert bushings, similar to automotive leaf spring eyelets, or control arm bushings. These rarely go bad. The only failures I've seen have been through powdercoating; the curing heat broke the bond and they walked right out of the shells. Replacing swingarm bushings is another DIY-hostile process. The removal is a P.I.T.A. installation requires a press.
     
  21. Rakillia

    Rakillia New Member

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    So don’t bother opening up the swing arm?

    Pullers came. Clutch frictions look newer and measured well within spec. Springs aren’t new but still in spec. I didn’t see a spec for the steels. Waiting to split the case and pull the oil pump till the jis drivers come
     

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