Somewhat modern 79 cbx

Hey, what projects are you planning or preparing for? CBX, other motos, workshop, WHATEVAH!
Salman_z8
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Somewhat modern 79 cbx

Post by Salman_z8 »

First time poster on this forum.
I come from the world of cb750s. Have rebuilt a few of those engines.

When i sold one of my cb750’s, a year ago, kind of became friends with a gentleman through whom i ended up acquiring a CBX engine and a 79 frame. Got the frame for the good price, because it was cut at the tail end past the shock mount.

No complaints there, infact i could have never brought myself to cut up a good frame, never have in the past of any bike really ... but that sort of lead to the idea of a better handling and lighter cbx.

Plan was simple, motor was supposedly good, and there really was nothing else.

So i sourced a gsxr 1100 front and rear end, off of a 95 watercooled gsxr.
50mm USD forks, 320mm rotors, 6 piston calipers .. that outa stop the sixer.

Found a cbx triple, used the steering stem to graft the gsxr front end. Great, super easy.

The swing arm is the braced one, a little long for my liking, but kind of want to stick with in a budget.

Since the engine had sat in my table for over a year, i finally got around to see if it spins over, not that it shouldn’t .. its a supposedly good motor. Well not so much.
One day, i’ll have em all finished.

Salman_z8
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Re: Somewhat modern 79 cbx

Post by Salman_z8 »

7939

This is how the frame is mocked up so far.
Front end fit is complete.
I put the engine in earlier, everything will line up great. Just gota make a sleeve for the swing arm pivot and two spacers.
But that was all great, till i got to the engine.

The engine wasnt turning over, starter motor was missing so i was going by the crankshaft cover to manually turn. Engine would rotate and back in a 20 degree motion.

So, a little PO’d, i took off the valve cover.
BTW, plugs were out, no carbs, and i had been spraying PB blaster in the plug holes for a couple weeks in efforts to not have problems. As the motor had been sitting for years.

So, valve cover came off, didnt take long to figure out that the cam sprocket had no bolts connecting it to the cam shaft. OK then. So someone was in here, and clearly tried to fix something.
More inspection revealed some plastic bits floating around in cam area by cylinder 6.

Decided to take it further, took the cams out to see if it would turn over, no luck there.

Started pushing on all the buckets to see if they were free.
All but 4. Crap.

Off came the head, and i found out why it was the way it was.
Found two valve flutes sitting on too of the piston, and the other two valves just bent, not sheared.

Exhaust valves of 4 and 5.

And the cam chain guide A, is just destroyed.

Engine had a crap ton of carbon, seems to me it ran too hot, anyone ?

Valve terrain has what i think are KW retainers, and shim under buckets. So possibly hopped up, and may be over revved.
I havnt measured the cams yet, but no scoring, dont seem bad at all.

794079457946794779417942
One day, i’ll have em all finished.

Salman_z8
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Re: Somewhat modern 79 cbx

Post by Salman_z8 »

Did some internet search for a few parts, and holy cow .. they are not cheap to say the least.
Any good used parts resources will be much appreciated, the chain guide A.

I will need at a minimum 4 new exhaust valves, 2 new guides, that is if the other 2 guides are also not cracked.

And what ever the rest of the valves look like.

Dropped the pan, and more guide debris there, but rest is pretty clean.
A little too clean infact.

Engine is now on the stand, probably the cylinder will come as well, but i wana clean everything befire that comes, just so i can do something with it without having to keep degreasing everything afterwards7944
One day, i’ll have em all finished.

Salman_z8
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Re: Somewhat modern 79 cbx

Post by Salman_z8 »

forensic help will be appreciated.
And if anyone has been ina similar situation, what else could have possible damaged in the bottom end if anything.
One valve seat has a deep gouge, i really hope that can be cleaned up.
No hole in the piston, also a gouge there.

I do not want to split the cases, if i dont have to.
One day, i’ll have em all finished.

daves79x
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Re: Somewhat modern 79 cbx

Post by daves79x »

Observe very carefully each pair of pistons as you rotate each through TDC. A bent rod will show up as a 'short' piston. Any doubt, take it all apart and carefully have each rod checked. I'd be a little wary of the other camchain tensioner as well. Modern, new ones are available now. $$$ though. As you are finding out, nothing about a CBX project is for the faint of wallet.

Dave

Salman_z8
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Re: Somewhat modern 79 cbx

Post by Salman_z8 »

absolutely, will check thAt.
So far only the guide A, seems damaged. Tensioner B is out and looks not bad at all, A seems ok but will look more when i pull the block.

And yes, parts are crazy expensive. And i thought i had paid too much for the engine to begin with.
One day, i’ll have em all finished.

patzx12
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Re: Somewhat modern 79 cbx

Post by patzx12 »

Hi Salman,
With the engine in that state it may be prudent to take the hit and do a full engine rebuild.

Salman_z8
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Re: Somewhat modern 79 cbx

Post by Salman_z8 »

Had some time today ( tine taken away from sleep lol)

First order of business was to clean the engine.
Everytime i touched that thing, it was just disgusting.

Engine was cleaned down as well as it could have been. Most of the paint is actually quite nice under all that grime.

PO had gone quite crazy with silicone on the engine.
Anyways, engine is clean.

Took the block off. Aftermarket gasket was there .. hmmm. Couple that with the strange brass looking super thin copper head gasket. Hmmm

Rods look good. Was getting curious, so took #1 out. Measures 64.49mm
Havnt measured the bores yet. I am assumjng its the std sized piston.

Pistons are casted ART ... are these stock ?
Ring gap for the too ring was way too much .. .022” that could explain the crazy carbon.

Bores look good, no crazy ridges, but cant see much cross hatching marks.

Will deglaze and measure.

New piston rings will be in order, and then check end gap.
Ever heard of tkrj rings ? Supposedly japanese

Camshaft appears stock and much with in spec.

Found a replacement guide A, not cheap.

David silver will probably be supplying the valves.

Any leads on exhaust guides ? Are they still listed ?

Thats all for now, still have the block and head to clean.

But cleaning is a priority before any work will continue.
One day, i’ll have em all finished.

Salman_z8
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Re: Somewhat modern 79 cbx

Post by Salman_z8 »

BTW will be needing a gas tank, which i dont have.
If someone has one they are willing to let go please pm me.

Not worried about dings, paint, damage or anything really.

Just message me what you got. Will be shipped to canada so keep that in kind for pricing

Thanks
One day, i’ll have em all finished.

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Re: Somewhat modern 79 cbx

Post by wyly »

Salman_z8 wrote:Had some time today ( tine taken away from sleep lol)

First order of business was to clean the engine.
Everytime i touched that thing, it was just disgusting.

Engine was cleaned down as well as it could have been. Most of the paint is actually quite nice under all that grime.

PO had gone quite crazy with silicone on the engine.
Anyways, engine is clean.

Took the block off. Aftermarket gasket was there .. hmmm. Couple that with the strange brass looking super thin copper head gasket. Hmmm

Rods look good. Was getting curious, so took #1 out. Measures 64.49mm
Havnt measured the bores yet. I am assumjng its the std sized piston.

Pistons are casted ART ... are these stock ?
Ring gap for the too ring was way too much .. .022” that could explain the crazy carbon.

Bores look good, no crazy ridges, but cant see much cross hatching marks.

Will deglaze and measure.

New piston rings will be in order, and then check end gap.
Ever heard of tkrj rings ? Supposedly japanese

Camshaft appears stock and much with in spec.

Found a replacement guide A, not cheap.

David silver will probably be supplying the valves.

Any leads on exhaust guides ? Are they still listed ?

Thats all for now, still have the block and head to clean.

But cleaning is a priority before any work will continue.
I found David Silver to be pricey and not an extensive selection. For new and used spares Bert at Six Center Motoren https://www.sixcenter.nl/index.html Bert may restore and sell more complete CBX's than anyone else on the planet. Others may sell parts Bert builds and rides CBX so he knows what works and what doesn't.

Louis has every spare you could possibly need- https://www.usedcbxparts.com/

Cam Chains-Vince and Hyde, V&H do high performance parts.
CBX a work in progress, still improving...GS1150EFE completed and awaiting modifications.....RD350, remnants in boxes scattered throughout the garage

Salman_z8
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Re: Somewhat modern 79 cbx

Post by Salman_z8 »

Thank you wyly.

I just ordered a chain guide from louis this morning.
I kinda figured pricey, but thats about the best bet.

Vince & hyde stuff is awesome, i got their literature they sent.
But frankly for a stock motor i couldnt justify the price for the A tensioner set, though its a great price for what it is and how much R&D has went into it, may be if it was somewhat hopped up.

Ordered a set of piston rings.

Need gaskets, and valves and guides.

Any leads on a gas tank ? What are they worth ? I dont mind whatever shape its in, the worse the cheaper lol

Also, silly question, what type of ignition to these run ?
Is there an ignitor box ? Cdi type box

Still need a starter motor.
One day, i’ll have em all finished.

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wyly
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Re: Somewhat modern 79 cbx

Post by wyly »

Salman_z8 wrote:Thank you wyly.

I just ordered a chain guide from louis this morning.
I kinda figured pricey, but thats about the best bet.

Vince & hyde stuff is awesome, i got their literature they sent.
But frankly for a stock motor i couldnt justify the price for the A tensioner set, though its a great price for what it is and how much R&D has went into it, may be if it was somewhat hopped up.

Ordered a set of piston rings.

Need gaskets, and valves and guides.

Any leads on a gas tank ? What are they worth ? I dont mind whatever shape its in, the worse the cheaper lol

Also, silly question, what type of ignition to these run ?
Is there an ignitor box ? Cdi type box

Still need a starter motor.
For all my electrical needs I go to SCM or CBX Performance, both are very helpful with advice answering questions.
Tank I bought a dented rust free tank for a $100. Where in Canada are you, Ted in Edmonton has a nice horde of cbx spares.
Starter motor I've been told a CB750 starter will work.
CBX a work in progress, still improving...GS1150EFE completed and awaiting modifications.....RD350, remnants in boxes scattered throughout the garage

Salman_z8
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Re: Somewhat modern 79 cbx

Post by Salman_z8 »

Is there a contact for ted ?
I believe, Al, that got me this motor might have actually gotten this from ted, if i recall correctly.

But Al is in NZ i believe, and i am looking to hustle here.
One day, i’ll have em all finished.

Salman_z8
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Re: Somewhat modern 79 cbx

Post by Salman_z8 »

Cb750, sohc at least have a different style starter motor mounts, being bolted at 90 degrees to the shaft, cbx has bolts in line with the shaft.
One day, i’ll have em all finished.

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wyly
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Re: Somewhat modern 79 cbx

Post by wyly »

Salman_z8 wrote:Cb750, sohc at least have a different style starter motor mounts, being bolted at 90 degrees to the shaft, cbx has bolts in line with the shaft.
I don't know much about the conversion actually, I was at local vintage bike night and another CBX owner "thought" I was having starter problems. He explained how he replaced his with a cb750 starter, I didn't pay much attention to the explanation as I knew there was nothing wrong with mine.
CBX a work in progress, still improving...GS1150EFE completed and awaiting modifications.....RD350, remnants in boxes scattered throughout the garage

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