Author Topic: 1972 CB750K2 (start from scratch) project. Cases back together  (Read 52174 times)

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Offline Davez134

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Decided to start another project since I like my current bike the way it is and need something to keep me from messing with it any more!

I got a motor for a steal from a friend of mine. (Started documenting that here: http://forums.sohc4.net/index.php?topic=139641.0 ) He did not have a K frame that was unaltered, but I luckily found one for sale in classifieds here from Finnigan. He even made a weekend trip to vegas to bring it to me! Also gave me a deal on Cognito Moto gsxr stem.

I'm not 100% sure exactly where I'm going with this one, but I know I want to keep it 2 up, 836cc, upgraded suspension and brakes, another daily rider (well every other day I guess, don't want my other K2 to get lonely)

Now some pics:
Motor

Frame

Gsxr stem

Finally, my other K2



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« Last Edit: January 24, 2017, 12:53:57 pm by Davez134 »

Offline edwardmorris

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Re: 1972 CB750K2 (start from scratch) project. Small leak!!! Damn!
« Reply #1 on: July 28, 2014, 01:28:51 pm »
Have I mentioned how much I LOVVVE those black fenders  ;D glad you got the frame, glad to have another K2 building alongside, I'll take all the motivation I can get ;)

Offline SOHC4 Cafe Racer Fan

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Re: 1972 CB750K2 (start from scratch) project. Small leak!!! Damn!
« Reply #2 on: July 28, 2014, 04:31:32 pm »
Vegas Dave,

I really like your other K2 bike -- very, very tidy!

I echo the comments about RTV.  Sometimes, a little is good for those nagging valve cover leaks, when you don't have the wherewithall to deck all of the mating surfaces, BUT it has to be used sparingly.

If you are going whole hog with a complete break down, I would port the head, too.
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)
2014 MV Agusta Brutale Dragster 800
2016+ Triumph Thruxton 1200 R (http://forums.sohc4.net/index.php/topic,170198.0.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)

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

Offline Davez134

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Re: 1972 CB750K2 (start from scratch) project. Small leak!!! Damn!
« Reply #3 on: July 28, 2014, 04:57:39 pm »
Vegas Dave,

I really like your other K2 bike -- very, very tidy!

I echo the comments about RTV.  Sometimes, a little is good for those nagging valve cover leaks, when you don't have the wherewithall to deck all of the mating surfaces, BUT it has to be used sparingly.

If you are going whole hog with a complete break down, I would port the head, too.

Thanks for the comments about other bike! As far as head, I have already messages Mike R. About it.

Offline SOHC4 Cafe Racer Fan

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Re: 1972 CB750K2 (start from scratch) project. Small leak!!! Damn!
« Reply #4 on: July 28, 2014, 11:08:27 pm »
Vegas Dave,

I really like your other K2 bike -- very, very tidy!

I echo the comments about RTV.  Sometimes, a little is good for those nagging valve cover leaks, when you don't have the wherewithall to deck all of the mating surfaces, BUT it has to be used sparingly.

If you are going whole hog with a complete break down, I would port the head, too.

Thanks for the comments about other bike! As far as head, I have already messages Mike R. About it.

You can't go wrong with some of Mike's artful porting.
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)
2014 MV Agusta Brutale Dragster 800
2016+ Triumph Thruxton 1200 R (http://forums.sohc4.net/index.php/topic,170198.0.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)

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

Offline Davez134

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Re: 1972 CB750K2 (start from scratch) project. Small leak!!! Damn!
« Reply #5 on: July 28, 2014, 11:54:48 pm »
He noticed something in my pics from the first link I posted. One of the holes for dowel is deformed from someone trying to force it on. Hope this doesn't screw me up.
« Last Edit: July 29, 2014, 01:29:15 pm by Davez134 »

Offline Davez134

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Re: 1972 CB750K2 (start from scratch) project. Small leak!!! Damn!
« Reply #6 on: July 29, 2014, 01:39:10 pm »
Here are the pics of my problem. I noticed the dowel as I was disassembling motor, but not until later did I see where it inserts into head. It definitely deformed the hole, but it's not too deep. Seems like it can be smoothed out and a new dowel will fit. Any suggestions? If the new dowel will fit tight without any play in it, will I be good to proceed with sending head to get ported?
Dowel in cylinder jugs

Deformity in head
Top right hole




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Offline edwardmorris

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Re: 1972 CB750K2 (start from scratch) project. Small leak!!! Damn!
« Reply #7 on: July 29, 2014, 02:36:45 pm »
Others will probably have better suggestions, but a while back I saw this

HTS 2000 Aluminum Repair

maybe it will help?

Offline Davez134

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Re: 1972 CB750K2 (start from scratch) project. Small leak!!! Damn!
« Reply #8 on: July 29, 2014, 03:37:22 pm »
Awesome, thanks! Gives me hope now.

Offline edwardmorris

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Re: 1972 CB750K2 (start from scratch) project. Small leak!!! Damn!
« Reply #9 on: July 29, 2014, 04:33:48 pm »
Awesome, thanks! Gives me hope now.
As long as you know Bill Benton, there is no need to ever lose hope ;) he can find you all the hen's teeth when you need them  ;D

Offline Davez134

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Re: 1972 CB750K2 (start from scratch) project. Small leak!!! Damn!
« Reply #10 on: July 29, 2014, 08:08:34 pm »
Well, I just ordered some. Looks simple enough, and seems like I can even repair a small chip in one of the cooling fins I just found. I'll post pics in a little while after I get it and test!

Offline anonimuso

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Re: 1972 CB750K2 (start from scratch) project. Small leak!!! Damn!
« Reply #11 on: July 30, 2014, 10:07:40 am »
I just want to say that I love what you did with your K2 bike. It looks awesome. I think I'll try to do something similar with my restoration.

Do you have a thread on the forum for that bike? Nevermind, I see the thread in your sig.
« Last Edit: July 30, 2014, 10:37:24 am by anonimuso »

Offline Davez134

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Re: 1972 CB750K2 (start from scratch) project. Small leak!!! Damn!
« Reply #12 on: July 30, 2014, 02:32:49 pm »
I just want to say that I love what you did with your K2 bike. It looks awesome. I think I'll try to do something similar with my restoration.

Do you have a thread on the forum for that bike? Nevermind, I see the thread in your sig.

Thank you very much! Nice to hear it was worth all the work :)

Offline Davez134

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Re: 1972 CB750K2 (start from scratch) project. Small leak!!! Damn!
« Reply #13 on: August 03, 2014, 06:47:11 pm »
Here are the pics of my problem. I noticed the dowel as I was disassembling motor, but not until later did I see where it inserts into head. It definitely deformed the hole, but it's not too deep. Seems like it can be smoothed out and a new dowel will fit. Any suggestions? If the new dowel will fit tight without any play in it, will I be good to proceed with sending head to get ported?
Dowel in cylinder jugs

Deformity in head
Top right hole




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So, I got the old dowels out of the jugs using the drill through and tap out from the bottom method I found recommended in a thread I found.  My plan is to smooth out the damaged/elongated dowel hole in the head with a dremel. Then, insert old dowel into the hole, clamping in place using the undamaged side as a guide. Next using HTS 2000 aluminum repair that was recommended, fill in the missing aluminum (since the hts 2000 won't bind to steel) Finally remove old dowels again after cooling, and if new ones fit snugly Ill send head out for porting. Fingers crossed. Going on a quick, much needed vacation, but new dowels and HTS2000 will be waiting here when I get back.

Offline Davez134

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Re: 1972 CB750K2 (start from scratch) project. Small leak!!! Damn!
« Reply #14 on: August 12, 2014, 12:04:48 am »
Well, the HTS 2000 repair was a bust for me. Nothing wrong with the product, I just don't have an oxy acetylene torch to get the aluminum hot enough for it to work. It worked great using Mapp gas on the smaller aluminum test pieces I used, but the head and cylinders dissipate heat too fast for it to keep up. Not all is lost though. New dowels fit snugly in head, so I'm sending it to Mike in the morning. The machine shop boring my cylinders is going to repair the fins on the jugs by filling with welds. Slow progress.

Offline calj737

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Re: 1972 CB750K2 (start from scratch) project. Small leak!!! Damn!
« Reply #15 on: August 12, 2014, 04:29:17 am »
I'm sure it will cost you more to have the shop fix it, but you'll be much better off with fixed properly and permanently.

From some of the pics, looks like Mike will be milling that head too  :o
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Offline Davez134

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Re: 1972 CB750K2 (start from scratch) project. Small leak!!! Damn!
« Reply #16 on: August 12, 2014, 09:07:58 am »
I'm sure it will cost you more to have the shop fix it, but you'll be much better off with fixed properly and permanently.

From some of the pics, looks like Mike will be milling that head too  :o

Yeah, I'm assuming that as well.  Going to have him do what even needs to be done to make it right.

Offline Davez134

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Re: 1972 CB750K2 (start from scratch) project. Small leak!!! Damn!
« Reply #17 on: August 20, 2014, 10:47:16 am »
More engine tear down while waiting for cylinder head. Studs out with relative ease.

Obvious removal method. I can reuse these right? :)

As expected, pieces of that red gasket sealer all over oil screen

PO/friend said "engine might even run with new battery, not sure" ...um think something missing from in this cover

Anyways, going good so far. Just slow progress as money is tight but I don't want to cut corners.


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Offline Davez134

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Re: 1972 CB750K2 (start from scratch) project. Small leak!!! Damn!
« Reply #18 on: August 21, 2014, 10:34:07 am »
Got cases split today. This is all new to me, since I just did the top end on my last engine.

Came apart pretty easily. I was looking at the crankshaft bearings, and while I'm obviously going to plastigauge them, I was wondering about this wear I can see. I'm talking about those darker spots. Some have it, some don't. There are no obvious gouges, and feel smooth. If wear is within spec, are these ok to reuse?




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Offline Davez134

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Re: 1972 CB750K2 (start from scratch) project. Small leak!!! Damn!
« Reply #19 on: August 21, 2014, 07:56:02 pm »
Another update, I've finally decided where I'm going with this project. I was thinking of using the gsxr front end with everything else close to stock.  After thinking about it for a while I'm scrapping that idea, as it would look out of place, and going mostly stock with exception of engine mods, exhaust, and handlebars. Color is still up in the air. 

Offline edwardmorris

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Re: 1972 CB750K2 (start from scratch) project. Small leak!!! Damn!
« Reply #20 on: August 22, 2014, 12:00:00 am »
Those bearings look pretty good, not as badly scratched up but of course, plastigage to be certain as you've planned.

Offline Davez134

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Re: 1972 CB750K2 (start from scratch) project. Small leak!!! Damn!
« Reply #21 on: August 22, 2014, 12:14:09 pm »
I want to clean these cases, get old paint off, but I was wondering about this bearing (pictured) in lower case. I want to take it out before I start cleaning in soapy water.  Necessary? It looks in great condition and moves freely. My question is, should I just use a drift and mallet to remove? And if so, do I need a new one, or can I reuse this one?



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Offline edwardmorris

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Re: 1972 CB750K2 (start from scratch) project. Small leak!!! Damn!
« Reply #22 on: August 22, 2014, 12:46:39 pm »
If you can, see if you can borrow a blind bearing puller from a local auto shop. I'd be nervous about pounding it out with a hammer and drift....Pulling bearings out will definitely do some damage to them, this one is pretty small so replacement shouldn't cost much.

Offline Davez134

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Re: 1972 CB750K2 (start from scratch) project. Small leak!!! Damn!
« Reply #23 on: August 22, 2014, 04:07:24 pm »
If you can, see if you can borrow a blind bearing puller from a local auto shop. I'd be nervous about pounding it out with a hammer and drift....Pulling bearings out will definitely do some damage to them, this one is pretty small so replacement shouldn't cost much.

Done. And new one on the way.

Offline Davez134

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Re: 1972 CB750K2 (start from scratch) project. Small leak!!! Damn!
« Reply #24 on: August 24, 2014, 04:21:29 pm »
Started measuring bearings today. First time, seems simple enough but just wanted reassurance I'm doing it right.

I cleaned/dried surfaces, laid top case on workbench. Laid plastigauge perpendicular against bearing surface, laid crankshaft into bearing, installed bottom case and torqued to spec. Loosened bolts, removed case, lifted crankshaft out and rotated to measure.




Looks like this one is ok. Seem right before I move on to the others?


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