Juddrussell's 1971 CT70HK0 Build

Discussion in 'Projects/Builds' started by juddrussell, Oct 9, 2018.

  1. juddrussell

    juddrussell New Member

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    Hey Guys!

    I have always wanted to pickup a CT70 to fix up and play around on. Late last week I was able to make that happen, I bought a 1971 CT70H model in candy emerald green. I was pumped to find a 4 speed model!

    Bike had the engine removed (engine is not locked up) and came with several boxes of parts that had been pulled off. So far I have noted that i am missing the following:
    -Carburetor
    -Carburetor intake manifold
    -Airbox
    -Engine Guard
    -Chain Guard
    -Consumables (Standard stuff that needs replaced anyway, i.e. bolts, tires, tubes, chain, battery, cables)

    I understand that it is my decision on the direction to take my build but I would really like input from you experienced guys (@racerx) on when a bike should be "street restored" or rock original patina and get it running. I want to be able to enjoy the bike but don't want to make stupid decisions that hurt the value of the bike for resale in the future. My fear would be taking the bike in the wrong direction if it seems to be a good candidate for a restoration?

    I wanted to start the thread so I could determine what I want to do with the bike before I begin to purchase parts.

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  3. racerx

    racerx Administrator
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    It really is your call to make. Best I can do is ask questions, for you to answer. Numero uno...what is your goal? IOW, given your druthers, how would you be using the bike...judged shows, trophy case, polishing it between rides to the far end of your driveway/street & back, parades/special occasions, limited use as with (a scaled-down version) a restored classic car, trail beater for the kids to ride as a learning experience, commuting to work on nice days, cruising around suburbia, gobbling-up 50-100 stretches of tarmac...or something in-between? They're all possible but they all have different requirements.

    The AWOL parts can be replaced with OEM service versions, NOS, reproductions or restored originals. Unless you need a specific date code to be on the carburetor flange, new repop should be fine. The only item on the list that might be better as a restored original is the engine guard; the reproductions are nice, in some ways nicer than original but...there are glaring differences in manufacturing details, they're also made from thinner walled tubing - which has both advantages and disadvantages.

    About the only things that are really tough to change, after the fact are paint and any structural changes, i.e. modifications that involve cutting/welding/bending. Powdercoating frame tins is a very bad idea, over the long term, imo. Sheetmetal and PC is a one-and-done proposition, the primary but by no means only, downside. Wheels & footrest parts are the only good applications for PC, on these bikes. That said, those items are so easy to blast & paint there's not much advantage.

    I'll cut things off here, for now. Some feedback is needed to further this discussion.
     
  4. juddrussell

    juddrussell New Member

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    I appreciate the quick response racerx! There would basically be two paths I would take on this bike (1 - build to sell or 2 - build to keep).

    1.) Build to sell: If it seems like bike is in good enough condition, I would consider either getting it to a complete and original state (running & together with new consumables: tires, bolts, chain, etc.) to resell or go the route of a street restoration. I would be interested in doing either of these based on the value it could sell for. I know some 100 point/concours K0's can go for over 5k but I don't believe that is the best direction for this bike.

    2.) Build to keep: I would say my primary goal for the bike would be something completely functional that I can rip around the neighborhood on, load up in the truck for camping trips to mess around on, and maybe ride to work on a rare occasion. No real interest in having it set in the garage unused. My search all originated from camping trips to state parks, wanting something to ride back and forth to the bath house or grab a bag of ice.

    My inclination would drive me to throw on a trail buddy inverted fork set, renthal bmx bars, rock the patina/faded paint, maybe do an 88cc overbore with a fast road cam, and possibly convert to 12v to run a more modern headlight (baja designs or something of the sorts).

    My fear would be that it would be seen as ruining an HKO in pretty good condition. If this is the case I would probably go for option 1 and look for a less complete bike and just do a ground up build with a frame and aftermarket parts.

    I would guess your recommendations for a replacement carb and intake would be based on the decision from the 2 paths above and ultimate engine goals.

    Agree completely on powdercoating on these things, I would much prefer to have the option of fixing small dents and such before painting and having the ability to touch up areas.
    Photodump for idea of condition/parts.

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  5. juddrussell

    juddrussell New Member

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    I’ve got full access to a bead blaster (glass bead) and will be doing the rim halves tonight. I’ve read the recommended paint for the wheels is duplicolor BCP103 caliper paint followed up by duplicolor clear coat, this caliper paint won’t require a primer on the wheel halves correct?

    This may be a dumb question but, I planned on blasting and polishing the hubs. Can the entire inside/outside of the hubs be bead blasted? Or does the inside need to be taped off?
     
  6. racerx

    racerx Administrator
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    Don't bead blast anything that's going to be polished...it'll multiply the amount of metalfinishing needed before polishing can be done. As for the wheel hubs, they can be glass bead blasted inside & out...it's a good way to de-rust the brake drum. I'd avoid blasting the aluminum surfaces, inside the hub though. They're far easier to clean without "profiling" (adding the bead blasted texture to) the surface.

    In my decidedly opinionated experience, there is such as thing as "mission creep". I started out a couple of decades ago with a titled, low-mileage, original-owner K1 and the same goal...a good bike for camping/trail riding that could be ridden to & from the trails. By the time I got done with the list of items to be replaced, there wasn't much left of the original bike. So, that one got back-burnered, slated for a full-on, 100-point, restoration. I sourced a rare JDM ST70 that had been abused, partially cannibalized for parts and left for dead. If you've been combing the various threads here for a while, it's my red custom Dax. Suffice it to say that after 24,750 miles (in its present configuration) it turned into something very different from my original goal. BTW, I did go offroading with it...visiting places I'd never dare risk a car; about 3-4 years ago, I finally had my fill of trail riding. It stills goes on camping trips, just gets ridden over nice, largely vacant, stretches of 2-lane highways.

    If you're going to build a highly modified bike, with lots of aftermarket parts...such as you listed...you could start with a rolling chassis, or less. With a complete new front end, requisite upgraded rear shocks and horsepower infusion, you'd likely do as well, or better starting with a frame, fuel tank & bracketry, seat latch, headlight & tail light, swingarm and a pair of wheel assemblies. Doesn't sound like much, does it? Fact is, you'll end up discarding far less this way...and spending less cash to do it. Tires, exhaust, fenders, cables, chain, bearings, lights, etc are all cheaper if sourced new. And, for a beater type build, you could substitute cheap & chineezy versions of non-critical stuff, such as the fenders & lights. You could take your choice of repop seat styles for less than $200, delivered. Rebuildable engines can be had cheap enough, though not in 4-speed/manual clutch flavor. It's possible to convert...via AHP 4-speed tranny and TB manual clutch kit, if you dislike a semi-automatic. FYI, there's ~$175 difference between an 88cc bore up kit and adding a 51mm stroker crank to make it 108cc. This just covers a few of the basics. You've got LOTS of options from which to choose.
     
  7. juddrussell

    juddrussell New Member

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    Good to know on the bead blasting of the hubs. Thank you sir!
    I agree, mission creep is real, especially once the mod bug bites! I’m probably going to move forward with getting the bike into a running/rideable condition without repainting. Any recommendations on bolt kits? I’ve seen a few vendors offer complete bike packages and with mine missing things from engine bolts to wheel bolts I figured a package might be worth it?

    I agree if I go heavy modified I may just look for a junk roller and tear into it while keeping this bike somewhat stock/simple. And yes o have seen your bikes, they are incredible. That is a very cool way to have a bike to thrash on + a beauty queen.
     
  8. juddrussell

    juddrussell New Member

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    Blasted the wheels tonight and went ahead and cleaned up the axles. Through them in a sealed bag to keep the moisture out until I paint them. There are a few dents on the rim edge of the rear wheel, any tips on best way to straighten these out?


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  9. racerx

    racerx Administrator
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    If the engine needs an overbore anyway, you can use that as a legit excus...ummm...reason to go with a bore-up kit. That's a well-accepted mod, reversible, too. Just retain the original cylinder jug for "someday". I would strongly recommend splitting the cases and going through the engine. There's a moderate chance the crank is worn and a high probability that the shift forks are toast. Now would be the time to replace these items and save yourself more open heart surgery on the same engine, in the not-so-distant future.

    For what you're doing, I'd just source stainless fasteners. If you decide to go for perfection, then the originals would get the nod...as in restoring them. FYI, I'd include all of the zinc-plated parts...axles, spacers, washers, seat latch, brake arms & cams, footrest pins, pivot bolt & spring, etc...i.e. everything that was originally zinc plated as part of that little project. Do `em all at once.

    BTW, blasting the hubs, then replacing the bearings (with sealed "2RS" versions) afterward keeps the bearing seats protected from erosion during the blasting process. I wouldn't reuse an original bearing. FWIW, the old seals can be cleaned & reinstalled...for aesthetics; they're not needed with sealed bearings.

    That looks like a vintage Trinco cabinet, I'm guessing 30" or 36" wide, made back when stuff was built to last. They're still a good outfit. Those rim halves look pretty good. Best way to keep blasted steel from developing flash rust is to choose a day when the dewpoint is below 60F. Short of that, either hit them with etching primer ASAP, or keep them warmer than ambient air temp. Sometimes, you can get away with leaving parts in the blast cabinet...with the light left "on", door closed. Incandescent bulbs makes a lot of "waste" heat, that can be put to good use. I'd expect the plastic bag to hold moisture and work against you. No biggie, a few seconds per rim half and they'll be clean again. Ball peen hammer and some light blacksmithing skill ought to straighten the rim edges. If not, it's metal (brazing or welding) and metalfinishing.
     
  10. allenp42

    allenp42 Active Member

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  11. juddrussell

    juddrussell New Member

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    I confirmed today that the engine is the original, serial numbers are 134 apart. Belownive added a few pictures of the engine. There’s a broken portion on the casing where a bolt mount is. Will I have any issues with this? Repairs recommended?

    Went ahead and purchased a stainless bolt kit for the. I will baggie up and save the originals I have for the future.

    Regardless of plans I need to purchase the following:
    -battery
    -2 tubes
    -spark plug and new wire/boot

    I’m considering just seeing if I could get the bike running as is and selling for a rougher condition bike to do what I want. If I do this I would just buy a repop carb and intake manifold with a cone filter.

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  12. juddrussell

    juddrussell New Member

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  13. juddrussell

    juddrussell New Member

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    Racerx, I’m just gonna paint the hubs the same as the wheels. So you are saying just leave the bearings in there, blast it and replace with rubber sealed bearings? I work at an electric motor remanufacturing company so we use 2rs bearings all the time! I probably have some on the shelf and yes it’s a 36” trinco, great setup. Have a large polishing tumbler next to it as well
     
  14. racerx

    racerx Administrator
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    You're well set up for this project.

    Yes, even though the original bearings will survive, especially if you have an axle in the bore during the blasting process, it's not worth the time & effort to attempt cleaning & reuse. Let `em do their last job, masking the seats...then drive `em out, taking much of the mess with them. Shouldn't take much to scrub-out any old grease, left behind inside the hubs. Decent quality wheel bearings (imho) start at $10-12 a copy, $18 buys top line NTNs. Yes, it's overkill but very inexpensive overkill. They'll almost certainly outlive the hubs...if not the bike(!)...where else will an extra $25 bill last that long? You'll want to reinstall the old dust seals, the wheels won't look right without them; with 2RS bearings, you're not asking them to do anything but dress the part;)
     
  15. juddrussell

    juddrussell New Member

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    Sounds good! Agreed good bearings are a cheap insurance..

    Anyone have carb suggestions for the bike if it remained stock or the 88cc overbore? I also need the intake manifold and an air filter setup. Suggestions?
     
  16. racerx

    racerx Administrator
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    The stock carb will feed 88cc & hotter cam. I'd go with the "fast road"/SL70 bumpstick. Dratv sells a repop version; the NOS variety is kinda scarce. You could go with a VM20 Mikuni carb. That's reportedly good for 50-ish top end with the bore-up & cam combo. I'm not entirely onboard with that...however...being highly opinionated doesn't mean that I'm "the last word" on the subject either, even with decades of experience. This one's your call to make. FYI, the induction assembly, from intake to air filter, is just a glorified bolt-on setup...easily swapped-out whenever the need/desire might arise.

    If you stick with a stock carb, or reproduction of the stock carb, you could use the stock intake & airbox.

    As for the broken upper motor mount...good news/bad news. The good news is that's it's the RH case half, the one without the SN. You could replace it with any Z50 or CT70 case half manufactured from 1968 to 1981 and have, mechanically/structurally, the same part. The bad news is that it'll likely be difficult matching the external appearance between the RH & LH halves. It's possible to have a pro shop weld-up the missing section, then precision drill the hole...but only if the intact portions can remain unmolested. Otherwise, it's going to look weird...in which case, an intact RH casting would make a LOT more sense.
     
  17. kirrbby

    kirrbby Well-Known Member

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    Bummer about the busted engine case. But it's only the right side. It's cheaper to just replace it. I just auctioned off a good one on eBay. It sold for $1+ shipping...about 10 bucks. But your bike has 3000 hard miles and 45 years on it, you're likely going to have to split the motor anyway.

    IMO, a stock original bike is pretty much always worth more than a modified bike. And it only takes one or two incorrect parts to turn people off.
    You could assemble the parts that you DO have and sell that bike for whatever it's worth, with little time invested. Then use that money, (plus some out of your pocket) to piece together a modified bike to ride. Otherwise, my vote would be to SAVE that fine green HKO. Make it complete, and mostly correct...whether it's restored to perfection, or just complete and running good.
     

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