1979 CBX Restomod

Hey, what projects are you planning or preparing for? CBX, other motos, workshop, WHATEVAH!
Z3n
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1979 CBX Restomod

Post by Z3n »

Finally getting around to starting this project - I found a craiglist bike for relatively cheap, and a buddy commissioned me to build him a restomod CBX. Here's what we started with:
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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:
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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:
Image

This is, IMO, the supermoto that KTM should have built. If you'd like to read about it, more details are here.

Here's a picture of my 1290 and the one I built at the track:
Image

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:
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And pulled the engine apart - took some hammering to get the top end off, as the previous owner had spraybombed the entire thing.
Image

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...
Image



Anyways, as it turns out, there is an Ontario bore kit in the bike, taking it up to 1130ccs.

They also a use head gasket which interestingly doesn't match the bores exactly:
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Anyways, after some fears about locating rings and such (the ring 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 (Hey NobleHops!), 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:
Image

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.

But until then, I've got a CBX in the garage in pieces, and any tips that members might have of good things to look out for when doing a rebuild of a questionable rebuild would be much appreciated!

Hope you all have enjoyed my ramblings, and safe riding out there!

steve murdoch icoa #5322
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Re: 1979 CBX Restomod

Post by steve murdoch icoa #5322 »

Welcome to the site, Z3n. An excellent first post.
From what you have shown it looks like some of us will be learning from you instead of the other way round.

Can't imagine riding a breathed-on KTM.
With ZERO experience on modern bikes i rode a stock 1290 Super Duke R on a street demo day. It was fantastic!

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Re: 1979 CBX Restomod

Post by NobleHops »

This is gonna be a blast. Thanks for including me in your build, and thank you in advance for taking us all along. If you maintain this thread as you go, help will indeed come out of the woodwork, including from me where I can.

Oh and your KTM supermoto is frankly awesome. I owned an MZ Baghira and spent some quality time on a Ducati Hypermotard, and quickly learned that if I continued to ride one I would soon be walking. Supermotos are the ultimate hooligan bike.

:text-goodpost: :text-welcomewave:

N.
Nils Menten
Tucson, Arizona, USA '80 CBX, sort-of restored :-)

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Re: 1979 CBX Restomod

Post by Jeff Bennetts »

A ZRX swingarm conversion on a CBX? ha, it will never work! :laughing-rolling:

Image
Image
Image

That's my CBX Z3n, I used to sell ZRX swingarm conversion kits. There was a past poster on the forum who did a complete ZRX swap front and back on his CBX, he fabricated his own triple trees and a bunch of other interesting modifications, it would do you well to do a search here and find his build thread.

P.S. I also happen to have a pile of ZRX stuff if you're in need of anything.
Keep us posted on your progress,
Welcome jeff

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Re: 1979 CBX Restomod

Post by FalldownPhil »

WoW !! Looks like a great project. Thank you for sharing it with us.
Here are a couple of things of note. 67mm is an 1170cc engine. While you are putting it together, you would do very well
to get in touch with "genesound" and use his viton valve guide seals and cam cap bolts. They are very reasonably priced (cheap)
and you will be happy that you did. The cam cap bolts are very prone to break when torquing the stock ones down. Trust me on this one.
I am looking forward to following your build.
Very Best,
Phil

Here is a link to Gene :-)
viewtopic.php?f=5&t=8998&p=69884#p69884
When you are up to your ass in alligators it is sometimes difficult
to remember that your objective was to drain the swamp !!

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Re: 1979 CBX Restomod

Post by Z3n »

FalldownPhil wrote:WoW !! Looks like a great project. Thank you for sharing it with us.
Here are a couple of things of note. 67mm is an 1170cc engine. While you are putting it together, you would do very well
to get in touch with "genesound" and use his viton valve guide seals and cam cap bolts. They are very reasonably priced (cheap)
and you will be happy that you did. The cam cap bolts are very prone to break when torquing the stock ones down. Trust me on this one.
I am looking forward to following your build.
Very Best,
Phil

Here is a link to Gene :-)
viewtopic.php?f=5&t=8998&p=69884#p69884
I've sent him an email - thank you for the recommendation!
Jeff Bennetts wrote:A ZRX swingarm conversion on a CBX? ha, it will never work! :laughing-rolling:

That's my CBX Z3n, I used to sell ZRX swingarm conversion kits. There was a past poster on the forum who did a complete ZRX swap front and back on his CBX, he fabricated his own triple trees and a bunch of other interesting modifications, it would do you well to do a search here and find his build thread.

P.S. I also happen to have a pile of ZRX stuff if you're in need of anything.
Keep us posted on your progress,
Welcome jeff
You were actually kind enough to send me some pictures and reply to a few PMs when I kicked this off, about a year ago! I appreciate the help, and I have indeed seen that thread. I'm doing things a little differently than he did, but I've gotten many good ideas from the threads here.
NobleHops wrote:This is gonna be a blast. Thanks for including me in your build, and thank you in advance for taking us all along. If you maintain this thread as you go, help will indeed come out of the woodwork, including from me where I can.

Oh and your KTM supermoto is frankly awesome. I owned an MZ Baghira and spent some quality time on a Ducati Hypermotard, and quickly learned that if I continued to ride one I would soon be walking. Supermotos are the ultimate hooligan bike.

:text-goodpost: :text-welcomewave:

N.
Was great to talk to you a few days ago! Gotta get all my stuff in order here so I can send it out - still need to split the cases and finish stripping the valves out of the head.

And yes, supermotos are a giggle and a half!
steve murdoch icoa #5322 wrote:Welcome to the site, Z3n. An excellent first post.
From what you have shown it looks like some of us will be learning from you instead of the other way round.

Can't imagine riding a breathed-on KTM.
With ZERO experience on modern bikes i rode a stock 1290 Super Duke R on a street demo day. It was fantastic!
Eh, I've picked up a few things here and there but there's still plenty more to learn!

I'm a huge fan of my 1290 Super Duke, it's currently my wife's weekend bike and I run it at trackdays when I have the time :)

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Re: 1979 CBX Restomod

Post by Jeff Bennetts »

You were actually kind enough to send me some pictures and reply to a few PMs when I kicked this off, about a year ago! I appreciate the help, and I have indeed seen that thread. I'm doing things a little differently than he did, but I've gotten many good ideas from the threads here.

Okay I remember now, you were looking for the spacer measurements for a 1200 swingarm?

Good luck with your build!

jb

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Re: 1979 CBX Restomod

Post by FalldownPhil »

FalldownPhil wrote:WoW !! Looks like a great project. Thank you for sharing it with us.
Here are a couple of things of note. 67mm is an 1170cc engine. While you are putting it together, you would do very well
to get in touch with "genesound" and use his viton valve guide seals and cam cap bolts. They are very reasonably priced (cheap)
and you will be happy that you did. The cam cap bolts are very prone to break when torquing the stock ones down. Trust me on this one.
I am looking forward to following your build.
Very Best,
Phil

Here is a link to Gene :-)
viewtopic.php?f=5&t=8998&p=69884#p69884
Whoopsie, your 67mm is more likely a 67.5mm taking it to 1146 or so. I was thinking 68mm, sorry :-(
By the way, love the Super Duke.
Best,
Phil
When you are up to your ass in alligators it is sometimes difficult
to remember that your objective was to drain the swamp !!

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Re: 1979 CBX Restomod

Post by 80 cbx dude #6216 »

I'm looking forward to seeing more!! 8) -Mike

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Re: 1979 CBX Restomod

Post by Z3n »

Jeff Bennetts wrote: Okay I remember now, you were looking for the spacer measurements for a 1200 swingarm?

Good luck with your build!

jb
Thanks!
FalldownPhil wrote: Whoopsie, your 67mm is more likely a 67.5mm taking it to 1146 or so. I was thinking 68mm, sorry :-(
By the way, love the Super Duke.
Best,
Phil
No problem - it is what it is, at the end of the day. :lol:

NobleHops wrote:This is gonna be a blast. Thanks for including me in your build, and thank you in advance for taking us all along. If you maintain this thread as you go, help will indeed come out of the woodwork, including from me where I can.

Oh and your KTM supermoto is frankly awesome. I owned an MZ Baghira and spent some quality time on a Ducati Hypermotard, and quickly learned that if I continued to ride one I would soon be walking. Supermotos are the ultimate hooligan bike.

:text-goodpost: :text-welcomewave:

N.
Let's see if you're still saying this after you see the absolutely filthy, wrecked parts coming your way. :lol:
80 cbx dude #6216 wrote:I'm looking forward to seeing more!! 8) -Mike
Ask and ye shall receive!


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:
Image
Tagged and bagged parts:
Image
Stripped side covers:
Image
Rotating engine mount makes working on it easy:
Image
That one bolt that's so easy to forget:
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And finally, cases split:
Image

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

Transmission close up:
Image

Lift out the transmission:
Image

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
Image
Image
Image

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
Image
Image
Image
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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).

So, with that, dear reader, it is now time for me to ask you the questions:
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. Also, is that the expected location of the holes in the bearing shells?

I also noticed these very nasty holes, that have all kinds of machining marks still remaining on them:
Image
Image
Image
As you can see in the bottom picture, that one wasn't even drilled in straight.
Is this expected? - EDIT: A quick perusal of ebay cases shows some others with the same holes, so I guess they're used for assembly or something?

Finally, the shop manual claims on assembly for one of the oil pump valves, it should go "large 14mm cap -> metal insert -> spring", but the way the oil pump was assembled was "14mm cap, spring, metal insert". From the design of the cap, it seems pretty clear that it should go the way it was assembled, not the way it is pictured in the factory manual.

More work on this tomorrow - hopefully will have the cases bare, and can send them off to NobleHops and the internals off for WPC treatment!

I'll also post my list of parts to be updated/replaced for review by the collective wisdom of the forum here :)

Thanks for reading, as always!

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Re: 1979 CBX Restomod

Post by daves79x »

Yessss! You're into it now. Don't worry about the hole plugs in the cases - they all look like that. Oil pump assembly is as shown in the two pictures in the manual. Bearing shells only go one way so oil holes are correct. They show pretty normal wear. I'd plastigauge every bearing (rods included). If they are to the low/middle end of spec, then I'd leave them. Any further out than that replace. For street use they'll be fine.

Now - when you get your cases back from Nils, they'll look so nice that you'll be tempted to leave them that way - don't! Paint each individual engine part as Honda did, then reassemble. It will look factory (if that matters to you), but more importantly, it will stay looking good for a long time.

Oh, in reply to your previous post about 'errors in the manual'. The manual is crystal clear about primary shaft timing - biggest error there is guys don't read. It's the very early ones that show CAM timing the wrong way. Very few other errors in any other version of Honda's CBX manual.

Keep us posted.

Dave

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Re: 1979 CBX Restomod

Post by Z3n »

daves79x wrote:Yessss! You're into it now. Don't worry about the hole plugs in the cases - they all look like that. Oil pump assembly is as shown in the two pictures in the manual. Bearing shells only go one way so oil holes are correct. They show pretty normal wear. I'd plastigauge every bearing (rods included). If they are to the low/middle end of spec, then I'd leave them. Any further out than that replace. For street use they'll be fine.

Now - when you get your cases back from Nils, they'll look so nice that you'll be tempted to leave them that way - don't! Paint each individual engine part as Honda did, then reassemble. It will look factory (if that matters to you), but more importantly, it will stay looking good for a long time.

Oh, in reply to your previous post about 'errors in the manual'. The manual is crystal clear about primary shaft timing - biggest error there is guys don't read. It's the very early ones that show CAM timing the wrong way. Very few other errors in any other version of Honda's CBX manual.

Keep us posted.

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

Here's the photo for the oil pump:
Image

As you can see, it indicates that it should be assembled cap -> plunger -> spring, but it was assembled cap -> spring -> plunger (which also seems to be the correct way by how the parts are designed).


Another interesting thing that you can see is there is no locking ring on my primary shaft - it's just held in place by the bearing retainer.
Image
Here it is assembled out of the cases:
Image

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 otherwise fine.

Follow up set of questions:
I assume the punch marks on the oil rotors should face outwards?
Also, should i replace the con rod bolts or nuts? The manual makes no indication that i need to.
Should i upgrade the primary drive gear to the one that is secured by a locking ring, or should I just leave it as is? I'm inclined towards just leaving it.

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Re: 1979 CBX Restomod

Post by jnnngs »

Hi,

I am just about to put my bottom end back together today. Some comments:
- For the oil pump, mine is assembled as yours is - your manual appears incorrect for some reason.
- For the primary shaft gear, they changed to the one with the locking ring from frame 20729. Mine is also an early one, and will be leaving as is.
- I am not replacing con rod nuts / bolts.
- I didn't notice orientation of punch marks on my oil pump

Paul.

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Re: 1979 CBX Restomod

Post by daves79x »

Think you are right on the oil pump spring - it's been a long while since I had one apart. If it only goes one way, then that's the way. You must be working from a late model manual. As Paul said, after a certain serial number in '79, the primary shaft had a locking ring nut. Yours is earlier. Caution is that the alignment marks for primary shaft timing are slightly different. Holler if you need a page or 2 copied from the early manual.

No mention of punch mark orientation on oil pump gears. Shows one of them facing out in one of my manuals. Re-use rod bolts and nuts. Only replace the primary shaft with the upgraded version if you are planning on installing the matching late model clutch basket. These 2 items were upgraded (at different times) to reduce clutch chatter. Functionally, it's fine the way it is. Caution - is the little aluminum plug with the small orifice still pressed into the alternator end of the primary shaft? If not, you need to make one. Meters oil flow into the alternator clutch plates.

After looking at your pics again, I see that the aluminum plug is indeed missing - did you take it out or is it gone? Needs to be there.

Rest assured that you did the right thing in tearing the engine down and checking everything. Looks like all's pretty well inside and you'll have a good looking and running CBX - AND piece of mind knowing you did it right.

Dave

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Re: 1979 CBX Restomod

Post by Z3n »

daves79x wrote:Think you are right on the oil pump spring - it's been a long while since I had one apart. If it only goes one way, then that's the way. You must be working from a late model manual. As Paul said, after a certain serial number in '79, the primary shaft had a locking ring nut. Yours is earlier. Caution is that the alignment marks for primary shaft timing are slightly different. Holler if you need a page or 2 copied from the early manual.

No mention of punch mark orientation on oil pump gears. Shows one of them facing out in one of my manuals. Re-use rod bolts and nuts. Only replace the primary shaft with the upgraded version if you are planning on installing the matching late model clutch basket. These 2 items were upgraded (at different times) to reduce clutch chatter. Functionally, it's fine the way it is. Caution - is the little aluminum plug with the small orifice still pressed into the alternator end of the primary shaft? If not, you need to make one. Meters oil flow into the alternator clutch plates.

After looking at your pics again, I see that the aluminum plug is indeed missing - did you take it out or is it gone? Needs to be there.

Rest assured that you did the right thing in tearing the engine down and checking everything. Looks like all's pretty well inside and you'll have a good looking and running CBX - AND piece of mind knowing you did it right.

Dave
If you'd be able to send over those pages that would be fantastic - more information never hurts!

I'll take a look for that aluminum plug - I didn't take pictures of everything but if it fell out it should have just ended up in the bag o parts for the alternator.

I haven't found anything egregious yet, just a few little surprises, like the bore kit. Should be real sweet when it's put back together :)
jnnngs wrote:Hi,

I am just about to put my bottom end back together today. Some comments:
- For the oil pump, mine is assembled as yours is - your manual appears incorrect for some reason.
- For the primary shaft gear, they changed to the one with the locking ring from frame 20729. Mine is also an early one, and will be leaving as is.
- I am not replacing con rod nuts / bolts.
- I didn't notice orientation of punch marks on my oil pump

Paul.
Thanks Paul! Appreciate the double check on those items, helps set my mind at ease.

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