1979 CBX Restomod

Discussion in 'Some Assembly Required' started by Z3n, Jul 2, 2016.

  1. Z3n

    Z3n Been here awhile

    Joined:
    Sep 3, 2006
    Oddometer:
    136
    A buddy commissioned me to build him a restomod CBX. Here's what we started with:
    [​IMG]
    I sent the carbs off to Jack at Old school carbs to get rebuilt properly, as they were seized and terrible, and after he finished them up, reinstalled them on the bike, tried to start it up, and got nothing. After a few weekends of idly tinkering with the bike here and there, I eventually discovered that the bike had been rebuilt at some point in the past, and the previous owner had reinstalled the ignition jackshaft out of time, as is easy to do with the errors in the old manuals.
    A little hackery with some gaffers tape:
    [​IMG]
    And she fired right up!

    At this point, though, I decided it needed to be torn down to be checked over right - in the process of diagnosing the ignition issue I had discovered a few other things, and realized I wouldn't be happy unless I completely checked every bolt and put everything back together myself.

    But before I came to that conclusion, I built something else - the Supermoto that KTM should have built, which you've may have already seen here.

    But apologies! You're not here for KTMs!

    Back to the CBX - I finally got the time to begin the teardown. Pulled the engine from the frame:
    [​IMG]

    And pulled the engine apart - took some hammering to get the top end off, as the previous owner had spraybombed the entire thing.
    [​IMG]

    At this point, I begin to spec out the bores, and I notice something strange...the honda spec says the pistons should be 64.5mm, but mine are just barely under 67mm. I double check my measurements, and sure as hell, the pistons and the very straight, nicely crosshatched bores are 67mm. What is this?!?!

    Props to anyone who can identify these pistons before scrolling down...
    [​IMG]


    Anyways, as it turns out, there is an Ontario bore kit in the bike, taking it up to ~1140ccs.

    They also a use head gasket which interestingly doesn't match the bores exactly:
    [​IMG]

    Anyways, after some fears about locating rings and such (the rings look, thankfully, brand new - I doubt this engine has ever been run with the bore kit, as the crosshatch is so fresh that it looks like it has never run since the rebuild where they installed the primary shaft out of time), I managed to find appropriate replacement head/base gaskets, piston ring clips, and I'll be reusing the rings.

    As I'm a sucker for cool stuff, the external stuff is all going off for vapor blasting by Restocycle, and most of the internals including the gearbox will be going off for WPC treatment, as I've always wanted to do a build with that engine treatment. I don't anticipate any performance gain from it, but I do hope it provides more reliability and long term wear benefits. I'll be replacing the cam chains, and other wear items while I'm in the engine, hopefully setting the bike up for 50k miles of reliable normal operation with nothing more than valve adjustments and normal maintenance.

    Tonight I managed to pull half of the valves, got hung up on one of them that needed to have a high spot knocked down before it would move smoothly out of the valve guide:
    [​IMG]

    I'll also be setting the bike up with a ZRX swingarm and forks, a Ducati Scrambler headlight, ABS, and a number of other things to get it looking like what I think we all dream of: A CBX made in 2016. I've got an open trackday that I do each year, and this year it's on October 3rd - the goal is to have the bike ready for that trackday. Following that test, we'll ride it around for a little bit, and then break it down again so the frame, wheels, and swingarm can be powdercoated, and all the parts can go off for a custom paint job, that is still TBD. I'll also be leaning on GP Frame and Wheel to do some measuring of the frame, to make sure it's straight, and to allow us to validate that rake, trail, and other numbers are in an acceptable range.

    Longer term plans include an RFID ignition, a more modern looking gauge cluster using the OEM gauges, and maybe a few other neat things, we'll have to see what happens!
    #1
    DELTATANGO, Bananapete, k-moe and 2 others like this.
  2. k-moe

    k-moe Long timer

    Joined:
    Jun 27, 2012
    Oddometer:
    6,078
    Location:
    100º W
    I also doubt that you'll get any significant gains from the WPC treatment, but I will say that the scooter engine I built with it was slick. When I checked ring gaps the piston glided through the bore like it had already been broken in.
    #2
  3. Z3n

    Z3n Been here awhile

    Joined:
    Sep 3, 2006
    Oddometer:
    136
    Yeah, I'm not expecting anything but hopefully reduced wear and a little better durability.

    This weekend's update!

    Weekend update:

    Had a chance to take the engine from where it was in the last set of pictures to stripped cases of side covers/accessories:
    [​IMG]
    Tagged and bagged parts:
    [​IMG]
    Stripped side covers:
    [​IMG]
    Rotating engine mount makes working on it easy:
    [​IMG]
    That one bolt that's so easy to forget:
    [​IMG]
    And finally, cases split:
    [​IMG]

    The old mechanic's check of vertical play in the conrods shows no vertical play, which is good.

    Transmission close up:
    [​IMG]

    Lift out the transmission:
    [​IMG]

    Here's some pictures of the crank bearing mating surfaces (click links for HUGE):
    http://i.imgur.com/KidLpHT.jpg
    http://i.imgur.com/S28ZpAe.jpg
    http://i.imgur.com/hPZR7fz.jpg
    [​IMG]
    [​IMG]
    [​IMG]

    And the corresponding side on the lower crankcase:
    http://i.imgur.com/KiL6WMY.jpg
    http://i.imgur.com/8hWAjV8.jpg
    http://i.imgur.com/LNdcD8V.jpg
    http://i.imgur.com/Kpz8axo.jpg
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]

    Transmission spec'd out perfectly, oil pump spec'd out perfectly (although someone had clearly been in there before, as one of the rotors was mounted in backwards, with the dot facing inwards).

    I also noticed these very nasty holes, that have all kinds of machining marks still remaining on them:
    [​IMG]
    [​IMG]
    [​IMG]

    A quick perusal of ebay cases shows some others with the same holes, so I guess they're used for assembly or something.

    So, with that, dear reader, it is now time for me to ask you the question:
    The bearings have some pretty odd patterns on them - they're not detectable by running your finger across them, but it is strange none the less. Anyone seen anything like this before?

    More work on this tomorrow - hopefully will have the cases bare, and can send the outside bits out for vapor blasting and the internals off for WPC treatment!

    Thanks for reading, as always!
    #3
  4. Mobil1

    Mobil1 Long timer

    Joined:
    Jan 12, 2016
    Oddometer:
    1,837
    Location:
    ?
    Next time , clean the motor up before you pull it apart. Dirt is never good , even if you're doing a total disassembly. Clean , clean , clean.
    #4
    Velocipede, FR700 and nickguzzi like this.
  5. Z3n

    Z3n Been here awhile

    Joined:
    Sep 3, 2006
    Oddometer:
    136
    Every part is going off to be treated, vapor blasted, or cleaned by hand, including passage cleaning. It'll get re-assembled in as near as cleanroom condition as I can get it. Not too worried about it.

    Plastigauged all the bearings - everything at around .05, spec is .08, very pleased with that.

    Interesting thing that you can see here is no locking ring on my primary shaft - it's just held in place by the bearing retainer.
    [​IMG]
    Here it is assembled out of the cases:
    [​IMG]

    Took me a minute to figure out what was going on there, looking for the ring nut that the factory manual claimed would be there. All parts are in good shape with no major wear.

    Besides that, cases are split, conrods pulled, bearings look exactly like the other bearings with some discoloration, but fine.

    Just gotta clean up the stuff, get it packed securely, make sure I have all of the parts I need for rebuild on order, and off we go!

    Also have an ultrasonic cleaner on the way for most of the bolts. Any recommendations on fluid/usage from those reading?
    #5
  6. Beezer

    Beezer Long timer

    Joined:
    Oct 26, 2004
    Oddometer:
    8,560
    Location:
    Anchorage, formerly Spenard (hub of the universe)
    you going to double check ring gaps? I would at least check that all the rings are installed right side up. other than that... lookin good
    #6
  7. OldDog

    OldDog non impediti ratione cogitationis

    Joined:
    Feb 20, 2005
    Oddometer:
    6,592
    Location:
    Kalgoorlie, Western Australia
    Mmmm nice little read and good to see a fellow KTM Motard nut also doing a CBX LOL.

    http://advrider.com/index.php?threads/ods-cbx.1021586/

    http://advrider.com/index.php?threads/supercharged-ktm-lc8-motard-build.936583/

    Can I strongly suggest you approach the guys one the CBXworld forum they will steer you straight and theres an incredible resource there. Also beware the early repair manuals had a few typo's! (actually sounds like you are aware of that, but the varieties of Primary shaft setup can catch you.)
    #7
    Ginger Beard likes this.
  8. Z3n

    Z3n Been here awhile

    Joined:
    Sep 3, 2006
    Oddometer:
    136
    I have checked in there as well :) Appreciate the heads up on the shop manual, I'll be validating carefully and have taken quite a few pictures during diassembly!
    They're non-standard rings, but I will validate they've been installed the right way up if the ring construction isn't symmetrical.

    Missed a few updates here I guess...you get them all at once!

    Parts out for WPC and vapor blasting.

    Got the ZRX forks fitted, loses about 1 inch of front ride height. Should still be in range of reasonable.
    [​IMG]
    And momentarily throwing everything together for giggles - those bars are far too tall, but what can you do, it was the only set of bars I had on hand:
    [​IMG]

    Getting rear swingarm spacer knocked up, then I'll need to get the swingarm cut and re-welded to clear the frame. Once parts show back up, ready for re-assembly, and we're off!

    Probably also going to have to machine up some sort of custom mount for a steering damper on the triples, as you do! Things are proceeding nicely :)


    -----------------------------------------------------------


    Time for an update!

    I first recieved the parts back from WPC coating, which turned out fabulously:
    [​IMG]
    Conrods/bearings:
    [​IMG]
    Refinished bearings:
    [​IMG]
    Oil pump parts:
    [​IMG]
    Shift drum:
    [​IMG]
    Wristpins, etc:
    [​IMG]
    And shortly thereafter, another pile of boxes:
    [​IMG]

    Pulling this stuff out of the boxes was pretty amazing:
    [​IMG]
    For an example of how little the vapor blasting process changes the metal, here's some etching from the PO in the oil pan:
    [​IMG]

    I also have to give a massive shout out to Restocycle here - Nils does amazing work, the parts look fantastic - in fact, the biggest thing that his work has exposed is how rough the OEM castings actually are:
    [​IMG]

    After I saw the covers on his bike I had to have the same style with the lettering picked out in b lack, and he went through the process of pulling the covers back out of the box, and worked through five attempts before he got something he was satisfied with sending over. The parts are so clean, the wear from the years shows up to contrast the paintwork - this is going to be a bike to be ridden that should look nice as well, so I think the raw and used look is a good one:
    [​IMG]

    I highly recommend him for any work you might need. I know he spent longer on the parts than he charged me for (I've been doing this for a long time, and I know how much work goes into doing things right, and he did the job right, unquestionably). I told him the goal for this bike was to get the engine looking relatively consistent to draw the eye to the engine as the massive block of engineering it is, and you can see that in the parts in the pictures - most of it is aluminum, but some of it is magnesium, and some of it is steel - and it all looks consistent, exactly as I asked him to do. Very pleased. Now I have to go through all the work of making sure that the parts that go into the these nice clean parts are actually clean enough to justify using them. :laughing

    He didn't even complain about how dirty the parts were...just compare this:
    [​IMG]
    To this:
    [​IMG]

    Finally, on to the CCT:

    I've received a number of random cam chain tensioner parts, and now that I have the CBX parts back, it's time to start prototyping. We'll see how things go in the next few days :)
    #8
  9. tragerbon

    tragerbon Been here awhile

    Joined:
    Aug 2, 2008
    Oddometer:
    184
    Location:
    Texas
    Keep the updates flowing, been checking this thread daily looking for more pics and info. Really enjoyed the KTM build, that's right up my alley, and I've always had a soft spot for those CBX's. Glad to see your doing something different with the rear end, the skinny on those monsters always looked silly.

    Thanks for sharing !
    #9
  10. 9Realms

    9Realms Drawn in by the complex plot

    Joined:
    Jul 23, 2010
    Oddometer:
    5,253
    Location:
    Central Mn
    Well done.

    +1 for sending stuff out to get cleaned and prepped right.

    Your on the right track. :clap

    OUTSTANDING.
    #10
  11. Z3n

    Z3n Been here awhile

    Joined:
    Sep 3, 2006
    Oddometer:
    136
    Thanks! I don't particularly care for that part of the job, so I'm happy to farm it out to a professional with the right tooling and desire to do the job right.

    More updates to come soon, then! :)
    #11
  12. AllBlak

    AllBlak Been here awhile

    Joined:
    Sep 5, 2014
    Oddometer:
    759
    Location:
    The Land of Nod
    Very cool
    #12
  13. photomd

    photomd Been here awhile

    Joined:
    Sep 29, 2007
    Oddometer:
    829
    Location:
    The Land of Cotton (SC)
    What a cool build. I read this and think back to an old article on the technical aspects of Mike Hailwood's six cylinder race bike. I think it was in Classic Bike and was about the RC174. There were different size main bearings, and as well as bunch of other tricks to decrease internal friction: what a cool engine. Looking at your build, I'm amazed Honda was able to build that engine at a profit: very fun to see the inner workings and your's looks amazing after vapor blasting. Anyway, post up more...it's a great read. :beer
    #13
  14. duckman

    duckman co conspirator

    Joined:
    Feb 1, 2005
    Oddometer:
    1,133
    Location:
    Corova milk bar
    awesome job, need more pictures
    #14
  15. mike

    mike Long timer

    Joined:
    Mar 2, 2007
    Oddometer:
    4,606
    Location:
    NE MO
    I'll tag along.
    #15
  16. k-moe

    k-moe Long timer

    Joined:
    Jun 27, 2012
    Oddometer:
    6,078
    Location:
    100º W
    Everything I've read says that they took a loss on every one they sold, and that Mr. Honda put it out as a showpiece, not a moneymaker.
    #16
  17. Z3n

    Z3n Been here awhile

    Joined:
    Sep 3, 2006
    Oddometer:
    136
    Those old RC 6 cylinders were incredible. I had a buddy over who's an engineer and he was blown away at how much tech went into the CBX, such as the 7 plain bearings in the cases - compared to his CB750s he loved, they were space age technology. I, of course, noticed none of this, which is telling as most of my engine time is spent inside of modern engines, which in and of itself is pretty incredible - besides a couple of things that don't really make sense (CCT design included, of course), the design felt completely within the bounds of normal against my 1290 SuperDuke or any of the modern bikes I've worked on, just a little bigger and heavier.

    Well, as usual I'm terrible at taking pictures while I work, but I did get the ultrasonic cleaner setup. Very handy, even if it doesn't make things as clean as Nils gets them, haha.

    Threw the head studs in to see if they could be saved:
    [​IMG]
    The water was clean but the ultrasonic cleaner immediately makes any surface grit cloud off the parts:
    [​IMG]
    And a few minutes later:
    [​IMG]
    The final product isn't quite good as new, but will work well enough for this bike:
    [​IMG]

    After that, spent some time cleaning any residual WPC material off the cams, reinstalled some of the head dowels, and got the cams in for tension testing on the new and old chain. That gave me some baseline values to shoot for with the new cam chain tensioner. From there, some measurements, some screwing about, and that led me back to the comfort of CAD, as it always seems to do:
    [​IMG]

    I'm still waiting on cam chain guides to show up for final fitting, but once those do, it should just be drilling some holes and making sure everything lines up, the chain is tensioned appropriately, and then doing the vertical tensioner.

    Also, look at this exhaust:
    http://www.samurider.com/?p=10412
    Probably not in the cards for this build but god damn.
    #17
  18. Noblehops

    Noblehops Misfit Supporter

    Joined:
    Jul 8, 2007
    Oddometer:
    240
    Location:
    Tucson, Arizona, USA
    Subscribed! Thanks for the good words man, it was a real pleasure working with you.
    #18
  19. Lounge

    Lounge Been here awhile

    Joined:
    Jul 2, 2010
    Oddometer:
    905
    Location:
    COS
    Nice!!

    Your timing couldn't be better. I'm negotiating a barn find CBX owned by an 80 year old gear head whose owned it since new!

    [​IMG]

    [​IMG]

    S
    U
    B
    S
    C
    R
    I
    B
    E
    D

    :lurk
    #19
  20. duckman

    duckman co conspirator

    Joined:
    Feb 1, 2005
    Oddometer:
    1,133
    Location:
    Corova milk bar
    i just noticed the air box is missing, my 81 750 had those cv carbs . i loved that bike but i don't miss it.
    #20