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Author Topic: 78 CB750 manx build  (Read 6494 times)

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Offline jsedacca

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78 CB750 manx build
« on: December 05, 2013, 08:25:32 PM »
This is my first SOHC project, so please bear with my questions as I go along.  I recently finished up a 69 cb350 semi-restoration, and had the urge to build a killer 750.  I searched craigslist, and was able to find this 78 CB750K with clean title for $1000.  It ran, rode, and stopped, but needed some attention.  I went back and forth on what path i wanted to take, and the trip to Barber vintage festival, and reading this forum solidified that I would go all out on the build.

While at Barber, I met Dave and Cheryl from Legendary-motorcycles who make fiberglass, and now, alloy tanks.  I went with the alloy Manx tank, and had it in my hands in 2 weeks.  It is a work of art, and extremely lightweight.

After getting the bike up on the lift, I could assess everything.  It appeared the motor either had a hg leak, or was leaking from the pucks as the front of the engine was covered in oil/sludge.  Before diassembly, I cut the frame, and mocked up a frame splice kit from Carpy.  I integrated the front tank mounts onto the front sleeves, which will be isolated with thick rubber washers/bumpers.

I tore into the top-end, and it was a blessing in disguise.  2 bolts on the cam towers were loose, and a cam journal was severely chewed up.  Everything else appeared to be in pretty good condition as I got deeper into the engine.
Once the head was removed, the cylinders came off, and then the side covers.

At this point, I took the motor out of the frame and split the cases as I knew I would be upgrading the internals/chains, and wanted to clean everything out.

An order was placed with Ken at cycle-x for their 849cc kit, super rods, stainless valves, beehive springs, gaskets, cam chain, HD primary chains, and all the necessary rubber/chain sliders.  I held off on the camshaft as I wanted opinions on which would be best for my application.  Its strictly a street bike, but when its taken it, it will be ridden hard so don't mind a compromise.

The cases were scrubbed, cleaned, and scrubbed some more with kerosene and numerous brushes to get everything spotless.  The crank journals all measure within spec so will just need to measure up the rods when they come in.

The front end will consist of GSXR forks, 17" harley spoked rims with custom spokes, and modern sportbike tires.  Below are pictures of the bike, and progress so far. 

Will post updates as more parts arrive, and progress is made.  Thanks guys

Jared

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Offline lwahples

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Re: 78 CB750 manx build
« Reply #1 on: December 06, 2013, 07:31:57 AM »
Nice start! Well on your way to a good looking bike.
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Offline Bankerdanny

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Re: 78 CB750 manx build
« Reply #2 on: December 06, 2013, 08:29:04 AM »
You've covered a lot of ground already, I'm glad you got a thread going. I look forward to seeing your progress and the final bike.
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Current: '76 CB750F. Previous:  '75 CB550F, 2007 Yamaha Vino 125 Scooter, '75 Harley FXE Superglide, '77 GL1000, '77 CB550k, '68 Suzuki K10 80, '68 Yamaha YR2, '69 BMW R69S, '71 Honda SL175, '02 Royal Enfield Bullet 500, '89 Yamaha FJ1200

Offline 70CB750

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Re: 78 CB750 manx build
« Reply #3 on: December 06, 2013, 08:37:33 AM »
holly crap, look at the tank!

Subsribed!
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Offline MoMo

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Re: 78 CB750 manx build
« Reply #4 on: December 06, 2013, 08:44:15 AM »
beautiful tank!   subscription entered...Larry
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Offline jsedacca

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Re: 78 CB750 manx build
« Reply #5 on: December 06, 2013, 10:56:49 AM »
Thanks for the encouragement guys. I spoke to the guy who will be assisting with the motor, and he recommends having the crank lightened/balanced.  Any thoughts/opinions on this?  I will have the trans gears undercut to avoid any "popping out" issues but didn't account for the crank work.  Falicon is local, but after looking at other prices (APE), they are pretty expensive for a simple balance/lighten.  Any thoughts/insight would be appreciated.  Thanks guys!

Jared
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Offline jsedacca

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Re: 78 CB750 manx build
« Reply #6 on: December 10, 2013, 06:58:31 PM »
Not too much progress but the parts are finally coming in.  Its like an early Christmas!! The majority of the parts from cyclex arrived yesterday and everything looks great.  The front GSXR forks also came in which are now on the shelf until assembly.  Tonight, I was able to remove the cyl studs without much drama.  I had one snap, but I was able to grab the remainder with vice grips and turn it out.

Do you guys recommend having the cases blasted before painting or just give them a good scuff/scrubbing?  Still deciding on a camshaft, so any help/insight would be much appreciated.
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Offline MoMo

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Re: 78 CB750 manx build
« Reply #7 on: December 10, 2013, 07:29:15 PM »
Look at tweakins turd thread to see what he did to his cases.  I usually just degrease, use a water bases parts cleaner at work, pressure wash rinse  and blow dry.  Mine look OK but his looks good...Larry
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Offline dakota

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Re: 78 CB750 manx build
« Reply #8 on: December 13, 2013, 12:25:21 AM »
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Offline jsedacca

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Re: 78 CB750 manx build
« Reply #9 on: December 16, 2013, 02:04:44 PM »
Just a little bit of an update. I was able to get a little bit of work in even with my mom visiting from up north.  I was able to disassemble the cylinder head, and is ready for the machine shop.  I'll leave the guide removal to them as I don't have a blaster to clean the carbon off before removal.

Couple more parts also came in from cyclex.  I got the cycleX primary chains, APE lower case studs, and the cycleX primary chain tensioner.  Still waiting on the beehive spring kit as it is currently backordered.

Stay tuned for more progress as I strip the cases of paint, and machine work is completed.

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Offline jsedacca

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Re: 78 CB750 manx build
« Reply #10 on: January 19, 2014, 06:23:47 AM »
It's been a while since I posted an update, but work has been getting done.  I finished cleaning/degreasing the cases and stripped them of paint before painting satin black.  I baked them at 200 for an hour, and then let them set for 1-1.5 weeks before working with them.

I sent my stock crankshaft into CycleX and had them send me a "Frog Leg" lightened/balance crank.  It is a work of art, and a shame its hidden.  The APE HD main studs were also installed into the upper case.  I measured for rod bearings and main bearings, and have some coming in from Yamiya.  I ordered them on 1/15, and they arrived 1/18 from Japan to FL.

To prepare the CycleX Super Rods for install, I checked the bolt stretch using a stretch gauge, and rod vise.  With the ARP lubricant, I was seeing the recommended .005" stretch at 23ft lbs on all rods.  They are ready to go once I plastigage the journals.

Last but not least to finish up the lower cases is the CycleX undercut gears.  They will be in this week, and will reassemble the trans for fitting. 

Stay tuned for more updates/progress as I will certainly have questions along the way.  Thanks guys

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Offline MoMo

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Re: 78 CB750 manx build
« Reply #11 on: January 19, 2014, 06:39:31 AM »
Looking good, you're right that crank looks like a beautiful,, modern sculpture...Larry
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Offline jsedacca

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Re: 78 CB750 manx build
« Reply #12 on: January 20, 2014, 04:22:05 PM »
Just a quick question for the experts out there.  I am using the APE HD main studs, but have upgraded to the cyclex super nuts.  I do not have the APE package anymore, and cannot remember what the tq specs are for the nuts.  If anyone can advise, it would be most appreciated. 

On another note, I have decided to bump up to the CycleX 915cc kit.  Stay tuned for more progress.
« Last Edit: January 21, 2014, 03:20:17 PM by jsedacca »
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Offline jsedacca

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Re: 78 CB750 manx build
« Reply #13 on: January 21, 2014, 03:24:02 PM »
The undercut gear clusters from CycleX arrived today, and I got them installed.  I had to order a thrust washer as one of my gears, had the washer built into one of the bushings.  I looked on parts fiche, and it appears to have been a change sometime thru the model year. 

Also plastigaged the rods, and brown bearings are what is called for.  Ordered the remainder of the bearings from Yamiya, and will hopefully have the cases sealed up in the next week or 2.
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Offline jsedacca

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Re: 78 CB750 manx build
« Reply #14 on: February 03, 2014, 09:06:03 AM »
Just a brief update after returning home from a cruise late last week.  The order from Yamiya came in, and assembled the rods onto the crank.  After that, the transmission was tested and everything appears to be working smoothly, and shifting as it should.

The chains were soaked in oil overnight, patted dry, and installed with the crank and main shaft with copious amounts of redline assembly lube.  Its tough to see, but the kibblewhite cylinder studs were also installed using red loc-tite.

I'm at a bit of a stand still until some dowel pins come in, along with an o-ring to seal the cases up.  Hope to have it done in the next week or so.

If there are any tips, tricks, things I have missed, PLEASE let me know before I seal the cases up.  All help/input is appreciated.  Thanks guys!

Jared
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Offline jsedacca

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Re: 78 CB750 manx build
« Reply #15 on: February 08, 2014, 03:11:30 PM »
After receiving in the missing o-ring, I prepared the crankcases for assembly.  After doing a lot of research on here, I decided to use gasgacinch for the sealant. Everything went together smoothly with only having to disassemble the cases once to fix a stupid mistake.

In the picture, you can see some new stainless fasteners from pro-bolt for the cases, and some old.  The old ones will be replaced.  I just wanted to tighten everything up so the gasgacinch cures.

Also reassembled the shift drum/shift mechanism and tested it.  The transmission appears to be shifting great so that is a relief. 

The next update will be with the cylinders being bored, painted, and prepped for assembly.

Thanks guys
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Offline bill440cars

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Re: 78 CB750 manx build
« Reply #16 on: February 08, 2014, 10:50:48 PM »


  Wow, just happened onto this build and all I can say is, I WILL be looking to see the finished project! WOW, VERY Cool!!!!!!!!!!!!
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Offline SOHC4 Cafe Racer Fan

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Re: 78 CB750 manx build
« Reply #17 on: February 09, 2014, 10:40:27 AM »
The motor is coming along nicely.  I am using the same combo of a Cycle X lightened and balanced crank, Super Rods, Race-Cut Trans and APE HD Studs.

Are you using a HD primary tensioner, too?
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Offline jsedacca

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Re: 78 CB750 manx build
« Reply #18 on: February 09, 2014, 11:11:12 AM »
Quote from: CB750 Cafe Racer Fan on February 09, 2014, 10:40:27 AM
The motor is coming along nicely.  I am using the same combo of a Cycle X lightened and balanced crank, Super Rods, Race-Cut Trans and APE HD Studs.

Are you using a HD primary tensioner, too?

I am using the cyclex primary tensioner. Thanks for the compliments so far guys
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