Author Topic: 72' CB750K2 Resto-Mod  (Read 14969 times)

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Offline SOHC4 Cafe Racer Fan

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Re: 72' CB750K2 Resto-Mod
« Reply #25 on: November 30, 2016, 10:33:34 PM »
That bare square looks a little funky.  I'm surprised they do that.  I guess they like to lay the powder on thick.
1975 CB550K1 "Blue" Stockish Restomod (http://forums.sohc4.net/index.php?topic=135005.0)
1975 CB550F1 frame/CB650 engine hybrid "The Hot Mess" (http://forums.sohc4.net/index.php/topic,150220.0.html)
2008 Triumph Thruxton (http://forums.sohc4.net/index.php/topic,190956.0.html)
2014 MV Agusta Brutale Dragster 800
2015 Yamaha FZ-09 (http://forums.sohc4.net/index.php/topic,186861.0.html)

"There are some things nobody needs in this world, and a bright-red, hunch-back, warp-speed 900cc cafe racer is one of them — but I want one anyway, and on some days I actually believe I need one.... Being shot out of a cannon will always be better than being squeezed out of a tube. That is why God made fast motorcycles, Bubba." Hunter S. Thompson, Song of the Sausage Creature, Cycle World, March 1995.  (http://www.latexnet.org/~csmith/sausage.html and https://magazine.cycleworld.com/article/1995/3/1/song-of-the-sausage-creature)

Sold/Emeritus
1973 CB750K2 "Bionic Mongrel" (http://forums.sohc4.net/index.php?topic=132734.0) - Sold
1977 CB750K7 "Nine Lives" Restomod (http://forums.sohc4.net/index.php?topic=50490.0) - Sold
2005 RVT1000RR RC51-SP2 "El Diablo" - Sold
2016+ Triumph Thruxton 1200 R (http://forums.sohc4.net/index.php/topic,170198.0.html) - Sold

Offline FridgeRaider

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Re: 72' CB750K2 Resto-Mod
« Reply #26 on: December 01, 2016, 09:12:16 AM »
Brush some clear nail polish over the serial number and that will keep the bare metal protected from the FL humidity.

I was going to pick up some decent model paint to do some touch up work. I figured I could find a black close enough so it doesn't stand out like it does now.

That bare square looks a little funky.  I'm surprised they do that.  I guess they like to lay the powder on thick.

They did lay it down thick, not sure if that helps durability or not. As long as it last 20 years, I'll be content.
1972 CB750K2 Resto-mod (836cc Upgrade) - http://forums.sohc4.net/index.php/topic,161782.0.html

Offline SOHC4 Cafe Racer Fan

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Re: 72' CB750K2 Resto-Mod
« Reply #27 on: December 01, 2016, 04:44:58 PM »
They did lay it down thick, not sure if that helps durability or not. As long as it last 20 years, I'll be content.

Not sure either -- if it makes it more durable or more prone to chips (or simply just a little heavier).  I doubt it will have any significant effect.  Keep on keeping on!
1975 CB550K1 "Blue" Stockish Restomod (http://forums.sohc4.net/index.php?topic=135005.0)
1975 CB550F1 frame/CB650 engine hybrid "The Hot Mess" (http://forums.sohc4.net/index.php/topic,150220.0.html)
2008 Triumph Thruxton (http://forums.sohc4.net/index.php/topic,190956.0.html)
2014 MV Agusta Brutale Dragster 800
2015 Yamaha FZ-09 (http://forums.sohc4.net/index.php/topic,186861.0.html)

"There are some things nobody needs in this world, and a bright-red, hunch-back, warp-speed 900cc cafe racer is one of them — but I want one anyway, and on some days I actually believe I need one.... Being shot out of a cannon will always be better than being squeezed out of a tube. That is why God made fast motorcycles, Bubba." Hunter S. Thompson, Song of the Sausage Creature, Cycle World, March 1995.  (http://www.latexnet.org/~csmith/sausage.html and https://magazine.cycleworld.com/article/1995/3/1/song-of-the-sausage-creature)

Sold/Emeritus
1973 CB750K2 "Bionic Mongrel" (http://forums.sohc4.net/index.php?topic=132734.0) - Sold
1977 CB750K7 "Nine Lives" Restomod (http://forums.sohc4.net/index.php?topic=50490.0) - Sold
2005 RVT1000RR RC51-SP2 "El Diablo" - Sold
2016+ Triumph Thruxton 1200 R (http://forums.sohc4.net/index.php/topic,170198.0.html) - Sold

Offline FridgeRaider

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Re: 72' CB750K2 Resto-Mod
« Reply #28 on: December 07, 2016, 07:30:18 PM »
I've been working on some minor parts; engine covers and the likes. here's some pictures.







I took an angle grinder to the battery box and drilled some new holes so that i could mount an M-unit, Rick's Reg/Rec combo unit, and reproduction starter solenoid off of it. The idea is every electrical part will be either upgraded or new reproduction parts to keep the same look (ex: electronic ignition, all turn signals and stems, key lock). I want wiring up the bike to be smooth sailing and hassle free, if there is ever such a thing with electrics.


 


The swing arm ended being an absolute pain to powdercoat. It barely fits in my small oven and took me three tries before being able to get it in without screwing up the dry powder. The first time, I straight up dropped it. That's why there a good deal of powder on the floor in the pic. I might have to upgrade my oven when it comes time for the crankcase halves.




On a different note: Does anyone know if Slingshot Cycles (site sponsor for braided brake lines) has a listed phone number somewhere so that I can contact them directly? I sent an email last week inquiring about purchasing a dual disc setup and still haven't had any response. I've bought from them before but went directly through the website.
1972 CB750K2 Resto-mod (836cc Upgrade) - http://forums.sohc4.net/index.php/topic,161782.0.html

Offline FridgeRaider

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Re: 72' CB750K2 Resto-Mod
« Reply #29 on: December 08, 2016, 08:32:05 AM »
PM sent re: Sling-shot

Thanks Cal! I have the Cruzin_image 836 pistons in the mail. I should be getting close to the point where I can take you up on your offer to transport them to your machinist the next time you swing through my part of town. Should I hold off on powder-coating the cylinders until after I have them bored out?
1972 CB750K2 Resto-mod (836cc Upgrade) - http://forums.sohc4.net/index.php/topic,161782.0.html

Offline FridgeRaider

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Re: 72' CB750K2 Resto-Mod
« Reply #30 on: December 08, 2016, 08:38:41 AM »
I'd coat before machining. I'll be there the week of 12/19 so we are good on crossing paths.

Perfect! Thanks for the info and assistance.
1972 CB750K2 Resto-mod (836cc Upgrade) - http://forums.sohc4.net/index.php/topic,161782.0.html

Offline SOHC4 Cafe Racer Fan

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Re: 72' CB750K2 Resto-Mod
« Reply #31 on: December 08, 2016, 09:52:50 AM »
Cal the Cross-Country Cylinder Courier!  Mighty nice of you.
1975 CB550K1 "Blue" Stockish Restomod (http://forums.sohc4.net/index.php?topic=135005.0)
1975 CB550F1 frame/CB650 engine hybrid "The Hot Mess" (http://forums.sohc4.net/index.php/topic,150220.0.html)
2008 Triumph Thruxton (http://forums.sohc4.net/index.php/topic,190956.0.html)
2014 MV Agusta Brutale Dragster 800
2015 Yamaha FZ-09 (http://forums.sohc4.net/index.php/topic,186861.0.html)

"There are some things nobody needs in this world, and a bright-red, hunch-back, warp-speed 900cc cafe racer is one of them — but I want one anyway, and on some days I actually believe I need one.... Being shot out of a cannon will always be better than being squeezed out of a tube. That is why God made fast motorcycles, Bubba." Hunter S. Thompson, Song of the Sausage Creature, Cycle World, March 1995.  (http://www.latexnet.org/~csmith/sausage.html and https://magazine.cycleworld.com/article/1995/3/1/song-of-the-sausage-creature)

Sold/Emeritus
1973 CB750K2 "Bionic Mongrel" (http://forums.sohc4.net/index.php?topic=132734.0) - Sold
1977 CB750K7 "Nine Lives" Restomod (http://forums.sohc4.net/index.php?topic=50490.0) - Sold
2005 RVT1000RR RC51-SP2 "El Diablo" - Sold
2016+ Triumph Thruxton 1200 R (http://forums.sohc4.net/index.php/topic,170198.0.html) - Sold

Offline FridgeRaider

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Re: 72' CB750K2 Resto-Mod
« Reply #32 on: December 08, 2016, 03:43:10 PM »
I got a response from Shaun @ Slingshot cycles and he did ask a couple of questions about how I'm going to run my setup. Then plan was to run the lines directly to the caliper and bypass the standard hardline. I removed the restricting insert on the second caliper prior to rebuilding. Should I have done that on the first one as well? I'm still a little fuzzy on it's purpose in the first place.
1972 CB750K2 Resto-mod (836cc Upgrade) - http://forums.sohc4.net/index.php/topic,161782.0.html

Offline bill440cars

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Re: 72' CB750K2 Resto-Mod
« Reply #33 on: December 08, 2016, 06:30:39 PM »


      Do I ever like your progress with this build! You accomplished quite a bit, since I was here last. Awesome work too. Really liking your Powdercoating! That is going to be One Fine Ride, when finished! Too bad about the issues you found, but I am glad that things can be worked out. Nice of Cal to help out like he is too. Some more of the "Family" atmosphere, around here, that I enjoy so much.  ;) You will have every right to be proud of this bike, when finished.  8) ;)
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Offline timbo750

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Re: 72' CB750K2 Resto-Mod
« Reply #34 on: December 08, 2016, 06:52:10 PM »
I got a response from Shaun @ Slingshot cycles and he did ask a couple of questions about how I'm going to run my setup. Then plan was to run the lines directly to the caliper and bypass the standard hardline. I removed the restricting insert on the second caliper prior to rebuilding. Should I have done that on the first one as well? I'm still a little fuzzy on it's purpose in the first place.
I did a twin disc conversion using the same brackets you have. I used the standard hard lines past the forks on both sides, mainly so that I didn't have to sucure a flexible line past the forks and the flexible line would most likely have to around the forks. I wouldn't worry about the size of the bit inside the caliper, its there so that the solid line will seal and I can't imagine it would affect flow too much as its more about pressure. Just upgrade the master cylinder and braided lines, also a bit cross drilling helps.

Offline edwardmorris

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Re: 72' CB750K2 Resto-Mod
« Reply #35 on: December 09, 2016, 11:55:53 AM »
Evan runs his lines directly into the caliper on his mostly stock 750. They're probably from SSCycles too.



http://forums.sohc4.net/index.php/topic,136061.msg1803704.html#msg1803704

Offline FridgeRaider

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Re: 72' CB750K2 Resto-Mod
« Reply #36 on: December 09, 2016, 01:37:55 PM »
Hey guys, thanks for the responses and support. I didn't realize that if I ran the braided brake lines straight to the caliper that I would have to run the lines on the outside of the forks ......and I just don't like that look. So now I'm back tracking to running hard-lines between the forks on both calipers. Which leads me to more questions. It looks like OEM hard-lines are still available for around $7, are they easy enough to manipulate so I can bend one to work on the mirrored caliper side? SSCycles sells a mirrored one for $30 the last time I checked, but I'm trying to save some money where I can. Also for the restricting insert, I removed it from the second caliper and either tossed it or misplaced it (oops). Will I absolutely need it in that caliper? If so, does anyone have one lying around they are willing to sell me.  ;D
1972 CB750K2 Resto-mod (836cc Upgrade) - http://forums.sohc4.net/index.php/topic,161782.0.html

Offline markreimer

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Re: 72' CB750K2 Resto-Mod
« Reply #37 on: December 09, 2016, 01:39:52 PM »
I'm not sure if this is the same situation as you, but I have a K4 and am running a braided line from my master cylinder directly into the caliper, running the line on the inside of the fork leg, works 100%. It's not a dual disc setup, just the standard single disc. Was very easy to setup.

Offline markreimer

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Re: 72' CB750K2 Resto-Mod
« Reply #38 on: December 09, 2016, 01:43:05 PM »
You can see it here, line runs straight in.

 


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Offline timbo750

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Re: 72' CB750K2 Resto-Mod
« Reply #39 on: December 09, 2016, 02:21:29 PM »
I manipulated the line by hand. Just took my time , it wont be an exact mirror as the guard mounting bracket is different on each side. I will get a photo for you.

Offline RAFster122s

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Re: 72' CB750K2 Resto-Mod
« Reply #40 on: December 09, 2016, 05:29:30 PM »
A bare line can be bought at the auto parts store, go to a Napa or similar to get a better quality line than the run of the mill auto parts stores have as their plating won't be nearly as good. Then a good tubing bender...just need a properly sized set of bubble flare tools or have the NAPA store that does machine shop work do it for you after you bend it to proper shape.
It may take you a few tries and the hardest bend is the one closest to the fitting near the caliper because if the line isn't straight it is very hard to get it to thread properly and it may not seal well.  So, you may need to leave a bit more room than the stock line has to ensure it is bent correctly if you do not have a vice mounted tube bender where you can put the bend more precisely.  Heating the line some helps it bend easier.  File smooth any cuts you make to the line and be sure to dress the opening as well so it doesn't have bits left over or a rough end or it is likely to split.
Best of luck!
David- back in the desert SW!

Offline FridgeRaider

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Re: 72' CB750K2 Resto-Mod
« Reply #41 on: December 10, 2016, 09:33:55 AM »
You can see it here, line runs straight in.

 


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Cool pic! Thank you for showing me an alternative option.

A bare line can be bought at the auto parts store, go to a Napa or similar to get a better quality line than the run of the mill auto parts stores have as their plating won't be nearly as good. Then a good tubing bender...just need a properly sized set of bubble flare tools or have the NAPA store that does machine shop work do it for you after you bend it to proper shape.
It may take you a few tries and the hardest bend is the one closest to the fitting near the caliper because if the line isn't straight it is very hard to get it to thread properly and it may not seal well.  So, you may need to leave a bit more room than the stock line has to ensure it is bent correctly if you do not have a vice mounted tube bender where you can put the bend more precisely.  Heating the line some helps it bend easier.  File smooth any cuts you make to the line and be sure to dress the opening as well so it doesn't have bits left over or a rough end or it is likely to split.
Best of luck!

I love having new tools to play with but unfortunately I don't do enough tube bending to justify buying one. I work mainly in a one car garage so space is a precious commodity for me. It's the reason I haven't bought a benchtop lathe .........or a CNC milling machine. Those things are sweet too.     

I manipulated the line by hand. Just took my time , it wont be an exact mirror as the guard mounting bracket is different on each side. I will get a photo for you.

That's what I'm going to do for my build, post a photo for me if you can.

In the mean time, here's some more pics of the progress. The front fender and fork ears were an early xmas present from my father. It's a considerably better look than dents and rusted out holes found in the original ones.




The seat I'm using has a cool story. About a year ago, My Dad and I took his '74 CB750 up to a small bike show in Tallahassee and outside was the usual assortment of odds and ends vendors. One of them was a guy who owned a (now closed) motorcycle shop and was trying to sell the last of his left over pieces. He had two identical CB750 seats in almost immaculate condition for $40 apiece. He said when the bikes were popular back in the day, people would buy custom seats for him to install and leave him with the practically new originals. He said he left them to sit on shelves in his workshop for 30 years before closing up his doors..........so naturally we talked him down to $25 apiece. For him to store those that long, he ended up making ~$0.83/year.  ;D


I powdercoated the stator cover in the chrome and then went back with some semi-gloss Black Testor paint bought at Hobby-Lobby to fill in the background.


1972 CB750K2 Resto-mod (836cc Upgrade) - http://forums.sohc4.net/index.php/topic,161782.0.html

Offline FridgeRaider

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Re: 72' CB750K2 Resto-Mod
« Reply #42 on: December 12, 2016, 09:19:38 PM »
Good thing I was looking for a challenge when I bought this bike.....because as as I delve deeper into the engine, I keep making unfortunate discoveries. When I had first dropped the oil pan I noticed a bad sign of sizeable chunks of metal and can now confidently say I found where the majority of it has come from. It looks like the PO either used to long of a screw or tried to torque screws down while something (fluid, dirt, etc) was at the bottom of the threads because he blew out the backing of three different M6 threads. One holds the oil pump in which isn't that big of a deal because it doesn't open up to the outside of the case. The other two he destroyed go straight through to open air. What are my options to repair or plug these things so I don't have oil seeping out past my bolts?









I also found this quite interesting, 2 out of the 5 lower crankshaft shell bearings look as if they were squished.






Not all is bad. I did blast and powdercoat the cylinders. This was the first time I've done something so intricate as far as trying to get an even coat in all the nooks and crannies between the fins. It's not perfect but I thought they came out well enough for a 40 year old survivor. Next step for them is a roadtrip with Cal to get bored out to 836cc.















P.S. I also had a broken bolt in the lower case but it came out easy enough with pliers. I figured I would add it to my write up to show the additional fun I've been having.

1972 CB750K2 Resto-mod (836cc Upgrade) - http://forums.sohc4.net/index.php/topic,161782.0.html

Offline FridgeRaider

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Re: 72' CB750K2 Resto-Mod
« Reply #43 on: December 13, 2016, 08:45:29 AM »
I would have those thru-holes welded closed on the backside, and make sure the threads are repaired before going to the trouble of powder coating them. Insert a steel bolt in the hole when welding to prevent the filler from buggering up the hole itself.

Hey, are there any options that don't involve welding. I dont own a welder nor the skills. I was think possibly redoing the threads with a long timesert and closing the ends up with JB weld.
1972 CB750K2 Resto-mod (836cc Upgrade) - http://forums.sohc4.net/index.php/topic,161782.0.html

Offline markreimer

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Re: 72' CB750K2 Resto-Mod
« Reply #44 on: December 13, 2016, 09:29:07 AM »
Could you take it to a welder? I've tried JB on engine case repairs in the past, not terribly reliable in my personal experience. If I had the engine apart to the degree you do, I would absolutely have it done by a welder. Then you know it's rock solid for life.

Offline RAFster122s

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Re: 72' CB750K2 Resto-Mod
« Reply #45 on: December 13, 2016, 12:14:22 PM »
You need to bake the cases to get the oil absorbed by the cases to come to the surface so it can be cleaned with acetone using several clean cloths with it to remove the oil.  If I remember Cal's advice you should TIG under a gas to get a much cleaner weld.

I am sure they can clarify the techniques to use.  Even if you use epoxy to fix it you would need to purge as much oil as possible.  To allow a better adhesion.

Another option is to buy another set of cases without the damage.
David- back in the desert SW!

Offline markreimer

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Re: 72' CB750K2 Resto-Mod
« Reply #46 on: December 13, 2016, 12:21:44 PM »
that's what I ended up doing. but only because I didn't feel confident enough in my skills to crack the bottom end... :-\

Offline riverfever

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Re: 72' CB750K2 Resto-Mod
« Reply #47 on: December 13, 2016, 06:09:58 PM »
Stator cover turned out real sharp!
http://forums.sohc4.net/index.php?topic=127186.0

"You wouldn't think that out here...a man could simply run clear...out of country but oh my...oh my...nothing but the light." -Ben Nichols

Offline FridgeRaider

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Re: 72' CB750K2 Resto-Mod
« Reply #48 on: December 13, 2016, 07:51:14 PM »

Another option is to buy another set of cases without the damage.


I'm trying my best to avoid that. Cal offered to pick it up (along my my cylinders) and weld it at his home base. A lot of the damage to the engine has had me scratching my head as to what the previous owner was thinking.

Stator cover turned out real sharp!

Thanks! I won't ever be a professional pinstriper or surgeon but I got it to where I liked it.
1972 CB750K2 Resto-mod (836cc Upgrade) - http://forums.sohc4.net/index.php/topic,161782.0.html

Offline RAFster122s

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Re: 72' CB750K2 Resto-Mod
« Reply #49 on: December 13, 2016, 09:33:30 PM »
Everything you have been doing has come out great! Many would have thrown in the towel on her so, kudos to bringing her back.  Cal will do a fantastic job on the case repairs.  Mad skills and he has created a little welding porn he has shared in various threads.  He has the gear and experience to do a solid repair.
BTW, you are not alone finding inside the case damage, just this is extremely case.  Makes you wonder what the PO was thinking.
David- back in the desert SW!