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Author Topic: 1978 CB750K — It never ends! (I am not a smart person)  (Read 132863 times)

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Offline SKTP

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1978 CB750K — It never ends! (I am not a smart person)
« on: April 05, 2010, 12:26:41 pm »
Here's how the bike currently looks. Summer 2017



Looks like PHOTOBUCKET got me. I stopped using it around page 27

http://s297.photobucket.com/user/ChristopherBywater/library/?sort=3&page=1

So I am finally getting around to rebuilding. My bike's tranny started getting all funky right before Christmas. So, since the motor is coming out I am goign to try and rebuild as much of the bike as I can. Right now the plan is:

- Media blast and powdercoat the frame, swing arm, triple tree, battery box, random bits, etc...
- New gaskets everywhere
- fix the tranny
- clean & polish everything
- rebuild and paint the forks
- new bearings, headset, swing arm, engine
- replace melted wiring
- upgrade the points/condensors. most likely get the Cycle-x Powerup kit http://www.cyclexchange.net/index%20pics/Power-up%20kit.JPG my mufflers are rusted and look terrible
- new primary chain
- new rings
- finish double-disk conversion (the second caliper never got mounted) and new more-modern master cylinder

I would love to hear any suggestions of other stuff I should consider doing. This will be my first major project...here's a brief history of the bike in pics

Round 1
I first bought it and cleaned it. It is my first motorcycle ever...used muratic acid on the tank rust (inside), stripped the old paint and rattle canned it...rebuilt the master cylinder, fixed wiring, had the carbs cleaned, new point and condensors

EDIT: Since PHOTOBUCKET has ruined most of the beginning of this thread...here's an "new" old picture



Round 2
New seat (thanks http://www.classiccyclecity.com/), powder coated Lester mags, new chain, bar risers and drag bars, super crappy mirrors, new ikon rear shocks, began conversion to double disk front, rotors resurfaced and drilled (thanks Chris Schumann, speedracer741_@hotmail.com he did an awesome job) also, my friend Taters painted the tank and chain guard. Real goldleaf and pin stripes...turned out so good, thanks Taters!


Round 3
The plan is outlined above. I plan on posting many, many pictures of the progress and how things went together here...and all the progress. As I said this is my first major rebuild. I want to make this bike look and run amazing! It was my daily driver for 2.5 years.


Round 4 (October 2013 — got it back together, started on the first kick. Did not seal the cam-tower-pucks and flipped a gear in the trans resulting in no 5th gear...complete tear down after 300 or so miles. 2nd time's a charm. Fingers crossed)


Round 5 (AUG 24th 2015 — fixing the leaks and transmission has turned into this...replaced almost everything that can wear out..reassembly soon)


May 22nd 2016 — Breaking it in...there is a head-gasket leak...but after doing the 1/4" cotton rope in jammed in around head gasket trick I am "leak-free" for the moment


November 27th 2016 — the motor is out again...going to get this thing leak-free

Here it is prior to the most current engine removal



May 22nd 2017 — Motor back in. New Cam tower pucks...OEM Honda base and Head gaskets. Hondabond used on Tach seal and cam-cover

« Last Edit: September 03, 2019, 11:47:41 am by SKTP »
1978k rebuild thread http://forums.sohc4.net/index.php?topic=68423.0
BIKE OF THE MONTH - OCTOBER 2017
2003 Ducati M800ie
1997 Honda CR-V
2004 Honda CR-V
1966 Honda S90

Offline SKTP

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Re: 1978 CB750K rebuild
« Reply #1 on: April 06, 2010, 06:14:54 pm »
Here's where I am at right now....I hope to pull the engine this weekend...























1978k rebuild thread http://forums.sohc4.net/index.php?topic=68423.0
BIKE OF THE MONTH - OCTOBER 2017
2003 Ducati M800ie
1997 Honda CR-V
2004 Honda CR-V
1966 Honda S90

Offline Old Scrambler

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Re: 1978 CB750K rebuild
« Reply #2 on: April 07, 2010, 08:18:22 am »
Nice start and a good looking commuter.........How many miles?  Tranny problems may be simple.....bent fork taps and or worn tabs.....  It looks like you bike had the usual over-charging battery leakage so I hope you now have a sealed unit. Also, you have more rust and corrision on your frame than ususal so I assume it sat outdoors for a while.  When you powdercoat be sure to keep the ground-wire surfaces clean and remove the swing-arm bushes and shock bushes and then cover the openings with a bolt and washers to prevent paint from entering the races. You may also want to do that on the neck. Fender washers and a long bolt work well and make a nice clean paint edge.
Dennis in Wisconsin
'64 Triumph Cub & '74 Honda CB750 Bonneville Salt Flats AMA Record Holder (6)
CB750 Classic Bonneville Racer thread - http://forums.sohc4.net/index.php/topic,135473.0.html
'63 CL72 Project(s)
'66 CL77 Red
'67 Triumph T100C
'73 750K3 Owned since New
'77 750F2 Cafe Project
2000 Aprilia Pegaso

Offline SKTP

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Re: 1978 CB750K rebuild
« Reply #3 on: April 07, 2010, 11:09:58 am »
Thanks for the frame prep tips and the sealed battery suggestion...right now I have the cheapest Autozone ATV/sports battery...I will upgrade. Yes, apparently it sat out under a tree for at least three years, when the previous owner had it...

Here's what I did last night...got that wiring harness and the airbox off (are wiring harness parts/connectors available anywhere? See melted connector above) Maybe upgrading it to modern fuses would be a good idea.

I need to do some research on cleaning carb and engine parts. I know there's a bunch on here, but feel free to add anything that you think might be helpful to a newbie. For example:
• can I use my wire-brush wheel on my grinder on the carb parts and engine parts or is that asking for trouble...
• If I clean the engine and have it media blasted, do I NEED to paint it?
• what's the square rubber box shaped bit hanging off the back of the battery box tab for?
• do I need to worry about the inside of my oil tanks rushing out when I drain it?
• how do you keep the metal ends of you cables (ie: choke, throttle, clutch) from rusting. those are some of the newest parts on my bike and they are all rusty and gross (to live VERY close to the ocean)
• when I drain the oil and pull the engine, how much MORE oil should I expect to come out...will it be crazy messy?
• thanks for all of your help. I'm sure I'll have 1 million more questions








« Last Edit: April 08, 2010, 02:00:50 pm by SKTP »
1978k rebuild thread http://forums.sohc4.net/index.php?topic=68423.0
BIKE OF THE MONTH - OCTOBER 2017
2003 Ducati M800ie
1997 Honda CR-V
2004 Honda CR-V
1966 Honda S90

traveler

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Solid green wire on a CB=ground.

Welcome to the world of scrubbing. ;D

Love the wheels and paintjob, BTW.

~Joe

Offline timdhawk

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take LOTS of detailed pics during your teardown...It will help me with put mine back together!  ;D
In deeper than I should be...

Offline SKTP

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Thanks for the replies so far....here's a shot I took of the bike right before the tranny started slipping...I have to get rid of that rear fender and taillight. Why did they design them so HUGE?

1978k rebuild thread http://forums.sohc4.net/index.php?topic=68423.0
BIKE OF THE MONTH - OCTOBER 2017
2003 Ducati M800ie
1997 Honda CR-V
2004 Honda CR-V
1966 Honda S90

Offline motocyconomad

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where can my gas tank get some of that love
yours looks super nice. The gold is gold leaf and not decals? nice.
those Lester Mags sure look good too where did you get em?

put oiltank in plastic bag and tape it
avoid wire/grinder I like Simple Green and scrub it with nylon brushes clean frame it helps fight the rusts
rubber box I think holds the blinker thingy
use gun oil to protect the little spots that are most susceptible to rust

Offline SKTP

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My good friend use to work at Foose and 'Overhauled' my tank. In exchange, I owe him drinks for life. The Lester Mags were a Craigslist find...

edit, just adding this link to my thread so I don't lose it...(carb syncing)

http://www.hondahobby.no/website.aspx?displayid=1593
« Last Edit: April 16, 2010, 12:06:52 pm by SKTP »
1978k rebuild thread http://forums.sohc4.net/index.php?topic=68423.0
BIKE OF THE MONTH - OCTOBER 2017
2003 Ducati M800ie
1997 Honda CR-V
2004 Honda CR-V
1966 Honda S90

Offline SKTP

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Workbench reinforced, ready to support the engine. If all goes to plan...I will have my motor out of the frame this weekend...

Planning on doing the "lay the bike on its side" method and then the "bribe friends with beer" move to get it on the bench.

Question: other than chrome covers (ie the points cover, etc...) are there any bolts/parts that I should remove prior to getting the engine out of the frame (not obvious things like wires, etc...) Should I loosen the case bolts with the engine in the frame? I will do more research for sure...but any tips posted here are greatly appreciated. First engine removal ever...
1978k rebuild thread http://forums.sohc4.net/index.php?topic=68423.0
BIKE OF THE MONTH - OCTOBER 2017
2003 Ducati M800ie
1997 Honda CR-V
2004 Honda CR-V
1966 Honda S90

Offline Toxic

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once the engine is removed, put the mounting bolts back into it, they provide something to hang onto during the lift.

it helps

Offline Nikkisixx

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I've never been a big fan of the paint scheme on the 77-78's but yours looks efin sweet SKTP!  Nice!   

Now for the statement of the patently obvious:
Solid green wire on a CB=ground.
;D 
I have the same mystery wire, and have no idea what it should ground?   

It is a proven fact that modifying a SOHC Honda in any way will bring on the apocalypse.

Offline SKTP

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The engine is out...now what? I need to take that thing apart...I need to do some reading. Also, Gasket kit suggestions, I'm guessing the more original OEM ones I can afford the better? (any tips at all, very welcome)...really cool to see the how the shift level works...can't wait to dig into it and find that tranny problem, stop the leaking and clean the grime...





edit: bookmarking this light bar
http://www.customdynamics.com/integrated_led_light_bars.htm

edit: bookmarking
http://trailtech.net/vapor.html
thanks jaguar!

edit: bookmarking
http://www.denniskirk.com/jsp/product_catalog/Product.jsp?skuId=201662&store=Main&catId=&productId=p210363&leafCatId=&mmyId=7720

edit bookmarking this battery:
http://www.carbon-speed.com/prod.htm

Bookmarking mini LED signals (thanks swellguy)
http://cgi.ebay.com/ebaymotors/Amber-LED-Mini-Bullet-lights-Yamaha-Roadstar-Blaster-_W0QQcmdZViewItemQQhashZitem5639780757QQitemZ370331354967QQptZMotorcyclesQ5fPartsQ5fAccessories#ht_1908wt_1167

Bookmarking:
http://www.charlies-place.com/450_1.html
and the parts guy Esteban Cruise
« Last Edit: May 05, 2010, 01:29:27 pm by SKTP »
1978k rebuild thread http://forums.sohc4.net/index.php?topic=68423.0
BIKE OF THE MONTH - OCTOBER 2017
2003 Ducati M800ie
1997 Honda CR-V
2004 Honda CR-V
1966 Honda S90

Offline shorterdanny

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Re: 1978 CB750K rebuild ••••••••• The engine is out!
« Reply #13 on: April 26, 2010, 11:08:22 pm »
coming along well mate..

one about your seat, did you have to modifiy it? or was it designed for the K8 ie opening right to left rather than the earlier k models left to right???
1983 Honda CBX 750
1978 CB750 K7

Offline SKTP

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Re: 1978 CB750K rebuild ••••••••• The engine is out!
« Reply #14 on: April 27, 2010, 10:26:27 am »
Yes, the seat was modified my Ricky Racer and Nippon...thanks guys!
1978k rebuild thread http://forums.sohc4.net/index.php?topic=68423.0
BIKE OF THE MONTH - OCTOBER 2017
2003 Ducati M800ie
1997 Honda CR-V
2004 Honda CR-V
1966 Honda S90

Offline knowsnothing

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I've never been a big fan of the paint scheme on the 77-78's but yours looks efin sweet SKTP!  Nice!   

Now for the statement of the patently obvious:
Solid green wire on a CB=ground.
;D 
I have the same mystery wire, and have no idea what it should ground?   

I don't think it goes to anything?!

1978 CB750k TBD - getting closer, 811 engine
1978 CB750k Blue - around town beater
1974 CB375F Faded Black - had to have that 6th gear
1976 CB400F Red - in many pieces
1973 CB350F TBD - in many pieces

Offline fastbroshi

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Re: 1978 CB750K rebuild ••••••••• The engine is out!
« Reply #16 on: April 27, 2010, 10:59:07 am »
   I wouldn't be surprised if it didn't lead to anything, my 550 had a spare ground circuit.  I must've checked my diagrams 100 times, and it didn't look like it was spiced in after the fact either.

+1 on the tank, very nice.
Just call me Timmaaaaay!!!

Offline SKTP

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Re: 1978 CB750K rebuild ••••••••• The engine is out!
« Reply #17 on: April 28, 2010, 06:12:57 pm »
Here's the shots from the weekend. It went pretty smoothly and everything came out pretty easily. I am pretty sure the bike must have been dropped on its right side at some point in its past. The back-bottom engine mount (that the foot peg attaches to) was slightly bent and so was the brake part that goes through the frame. Both where slightly hard to get out due to the slight bend, but they both came out with the help of a metal bar and a rubber mallet.

I had two friends help lift the engine out. It wasn't that difficult at all...

















don't powder coat your master cylinder. This is how it will look after 2 years:


Here's a couple of pics of my friend's 76K's ignition/key location. I plan on moving mine there to keep the bar uncluttered


1978k rebuild thread http://forums.sohc4.net/index.php?topic=68423.0
BIKE OF THE MONTH - OCTOBER 2017
2003 Ducati M800ie
1997 Honda CR-V
2004 Honda CR-V
1966 Honda S90

Offline RAF122S

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Nice work on the bike disassembly so far.
There are some Vintage Connection kits that should be able to help you on the wiring.
Check for wire rot and how flexible the wires are near the ends. They should all be similarly flexible for the same gauge size.
Any wire that's overheated and crinkled insulation I would recommend you change the entire run of that wire.
The excessive current will make the copper discolor and change it's resistance and the wires don't work quite the same after that...
Lived with that on a auto wiring harness rebuild...

Soda blasting does a nice job on removing oxidation without damaging paint that's well adhered and is good  for aluminum parts as it restore a factory clean look. Best of all, water clean up.
Just have to be careful not to get the soda in the engines or carbs.
Other media will change the finish on the aluminum, whereas soda will change the patina of the original aluminum like a sand or glass bead will. Plastic beads will strip paint and I think if I recall correctly they will not change the finish if not used at an excessive pressure.

With Soda blasting a hot water rinse, wash and air dry is generally all you need after a soda blast session.
Clean up is to rinse the soda into the storm drain or yard...
You can make a cheap soda blaster from an air tool blow gun attachment (pistol style is easiest to work with for long periods) and a section of clear plastic tube and a metal rod for the end of the tube to be taped to.
Slit in the hose about 2-4 inches from the tip half way through and insert the metal tube of the blow gun and it syphons the soda into the compressed air stream.

David
David- back in the desert SW!

Offline SKTP

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Slow and steady wins the race? I hope so...Here's what I did yesterday...

- Valve cover is off. Technically it should not be the gold/orange color right? That's lacquer build up? Do I have to clean it? I'm guessing that I most likely should. Can I just unbolt the head and leave the springs/valves and cams alone? This all started due to a transmission problem...lots more reading to do

- The tach drive. Do I need to bend that tab down to unbolt it? (green arrow)

- Busted shifter fork? I found that little bit of metal in my oil pan. Its a shirt fork tip right? I an thinking that is the cause or a large part on my transmission problems.

Please keep in mind this is my first teardown/rebuild ever

My Cycle-X full gasket set arrived. WOW that's a lot of pieces

- I plan on reading a lot about polishing






Before:

Used these on half:

After some tooth brushing:

Do I bend this (the tab) to remove the tach drive?

Does this look normal?

Shifter fork chunk?


Thanks for any and all comments, tips or suggestions
« Last Edit: May 14, 2010, 11:31:41 am by SKTP »
1978k rebuild thread http://forums.sohc4.net/index.php?topic=68423.0
BIKE OF THE MONTH - OCTOBER 2017
2003 Ducati M800ie
1997 Honda CR-V
2004 Honda CR-V
1966 Honda S90

Offline fastbroshi

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Some of your pics aren't showing up. That discoloring is normal I think, though it looks like yours had some high miles on it.  I'd clean it like you are.
Just call me Timmaaaaay!!!

Offline SKTP

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I think its just a photobucket slowdown...maybe hit refresh a couple times?

Any tips on removing the Carb-boots without damaging them? They seem to be Really, really on there...
1978k rebuild thread http://forums.sohc4.net/index.php?topic=68423.0
BIKE OF THE MONTH - OCTOBER 2017
2003 Ducati M800ie
1997 Honda CR-V
2004 Honda CR-V
1966 Honda S90

Offline andy750

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Any tips on removing the Carb-boots without damaging them? They seem to be Really, really on there...

Hairdyer works wonders. I just did this on some really stubborn boots and they popped right off after 30 secs -1 min of hot blow dry ;)

Current bikes
1. CB750K4: Long distance bike, 17 countries and counting...2001 - Trans-USA-Mexico (CB750K4), 2003 - European Tour (CB750K4), 2004 - SOHC Easy Rider Trip (CB750K4), 2008 - Adirondack Tour 2-up (CB750K4) , 2013 - Tail of the Dragon Tour , 2017: 836 kit install and bottom end rebuild. And rebirth: http://forums.sohc4.net/index.php/topic,173213.msg2029836.html#msg2029836
2. CB750/810cc K2  - road racer with JMR worked head 71 hp
3. VStrom DL1000 2003
4. XLR650L 2006

Where did you go on your bike today? - http://forums.sohc4.net/index.php?topic=45183.2350

Offline climbingaz

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I think its just a photobucket slowdown...maybe hit refresh a couple times?

Any tips on removing the Carb-boots without damaging them? They seem to be Really, really on there...

Heat gun worked for me.

Offline KB02

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Shifter fork chunk?


That little piece looks more like a bit of piston ring than shifter fork.  ??? ???

The discoloration looks normal for a bike that has been ridden hard with a lack of oil changes. Most engine are not quite that dark on the inside. It looks like that sucker was run HOT. Not bad, per say, though.

As for the tab on the tach gear, yes, just bend that down. The tab is there to keep the bolt from backing itself out and dropping into the valve train.

To take off the head, you will need to take out the cam and cam towers. The valves and springs do not need to come out, but since you have it at that point, it wouldn't be that bad a time for an examination.
1978 CB750K Project
2000 Ducati Monster
...and a pedal bike

Join the AMA today!!

My project thread Part I: K8 Project "Parts Bike"
My project thread Part II: Finishing (yeah, right) touches on Project "Parts Bike"

 

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