Author Topic: 1972 CB750 Four K2 -- Rebuilt to NEW OLD STOCK -- PIX ON PAGE 50  (Read 241109 times)

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Offline RRRToolSolutions

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #250 on: January 09, 2014, 01:28:44 PM »
Ed, I bought my 1974 Honda for $112 on eBay. The bike had sat out in the weather for years without plugs.... it needed lots of work and it was going to take more than just a clean-up of the bores because there was extensive pitting. The 836cc big-bore took care of it. From there, the head needed new valves, guides, and a valve job. I decided a stock 750 was going to be boring, so having the head built and ported by a local legend here in the Carolinas had to happen. Long story short, the engine ran so darn well that it lifted the front tire in 1st and 2nd with stock gearing just before the 8,000 mark. The engine pulled like crazy, but I could not enjoy it. Stock rods do nasty things when turned beyond their limit of 8,500 rpm. Buzz told me repeatedly that it wasn't "if", but "when" the rod caps were going to fail and the rods got pushed through the crankcase like a grenade. Maybe the rear locks up, but almost certainly it's going to drop a lot of oil on the rear tire and not when you're expecting it. I believed him. The stock CB750 K series uses 14 lbs/feet - low performance rods/bolts. Stock, these normally won't pull or make power over 8,000 rpm, but porting changes all of that. My heavy studs, Carrillo Rods, Dyna 2000, and CR29 Smoothbores all came about because that porting works!

I personally would not do it yourself, it's more than smooth and more than big. It takes velocity to fill a cylinder after the valves start to close. You'll need a bigger cam and heavier springs to close the valves - it is a viscious cycle of events. Hard to say "stop", but I will tell you stock rods and high rpm cannot be mixed. Regards, Gordon







« Last Edit: January 09, 2014, 01:31:57 PM by Ilbikes »
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Offline Terry in Australia

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #251 on: January 09, 2014, 01:55:23 PM »
That's a beautiful bike Gordon, something that Ed can aspire to as he toils away in his snowbound winter bunker. I agree with all of the above, but if Ed keeps his engine stock and just cleans up the ports, he shouldn't need to worry about all of the go fast goodies as long as he doesn't ride it outside of it's original design parameters.

He's already got a mild(ish) street cam and heavy duty springs if he wants to use them, but he's said that he's going to go back to stock items, so I think that if his bike won't be seeing too much redline action, it should just be a a good strong stocker.

As you've said above, one thing leads to another when you're building a hotrod engine, and quite often the end result can be disappointing, with increased wear, blown head gaskets and oil leaks (all of which I've experienced over the years) so a nice stock engine that is capable of doing lots of miles reliably over an engine with license losing potential but questionable performance and reliability wins hands down, IMHO.

I've got a friend who owns some really exotic motorcycles here in Melbourne (4 x CB1100R's, 2 x Bimota's, 1 x RC30, CX500 Turbo, etc etc) and he keeps them all stock standard. When we discussed hotting up old bikes his reply was that he enjoyed their reliability, and if he wanted to go faster, he'd just buy a faster bike. I couldn't help but think he was making a lot of sense. Cheers, Terry. ;D
I was feeling sorry for myself because I couldn't afford new bike boots, until I met a man with no legs.

So I said, "Hey mate, you haven't got any bike boots you don't need, do you?"

"Crazy is a very misunderstood term, it's a fine line that some of us can lean over and still keep our balance" (thanks RB550Four)

Offline edwardmorris

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #252 on: January 09, 2014, 02:47:09 PM »
Oh wow, that is quite a resto Gordon, nice work!

Yea, I will be keeping it stock because I really want this to be my lifetime rider. Maybe my next bike will be a racer (I blame your black engine Terry! I really want a second one now  ;D). Just got a stock cam and springs from Whaleman -> THANK YOU. Been working a lot to try and make up for lost time so haven't had a chance to inspect these and post pix yet. I will not be using the HD springs on this bike, but I may use the 41-a webcam should the stock one not pass. Porting, like Terry said, will be to a small extent only, nothing hyper like tracing out the gasket and opening ports full blast. Will be doing my best to keep it 100% stock, except for the initial Terminator 1 look (dented tank will be painted red and so will the cracked side covers and a fairing  :P). Once I have a rider, I will start saving up for a Yamiya body kit and with any luck, a better set of stock pipes to complete the stock look.

Still waiting on the head and not having much time at home to do anything useful. Was thinking about undoing the wheels completely to get the hubs etc cleaned and see what can be salvaged in the small chunks of time I find. Will the spoke wrench from vintagecb750 : #8,9,10 & 11 nipple sizes be enough for both the wheels?

Offline Terry in Australia

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #253 on: January 09, 2014, 03:00:51 PM »
G'Day Ed, Re: your wheels, depending on what your spokes are like. If they're rusty, it means that the zinc plating has given up the ghost, so polishing them will only be usefull until they start to rust again, once the polish has washed off.

Spokes are cheap on eBay though, so don't waste money on a spoke wrench, cut the old spokes with bolt cutters, (cutting them close to the hubs will make 'em easier to remove) clean up your hubs and rims (if the rust isn't too bad in the rims once you've removed the tires, but quite often the rust between tire and rim will make the rims dangerous to re-use) and buy some new spokes.

If you're gonna re-lace and true them yourself, take some pics of the pattern first to ensure you get it right, measure the offset (centre of hub to centre of rim) and just use a flat tip screwdriver with a notch cut out in the middle of the blade for the top of the spokes to screw the new nipples onto the spokes. Cheers, Terry. ;D
I was feeling sorry for myself because I couldn't afford new bike boots, until I met a man with no legs.

So I said, "Hey mate, you haven't got any bike boots you don't need, do you?"

"Crazy is a very misunderstood term, it's a fine line that some of us can lean over and still keep our balance" (thanks RB550Four)

Offline edwardmorris

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #254 on: January 09, 2014, 08:58:44 PM »
Thanks Terry, I took a look when I got home and it looks like the rear wheel spokes are pretty rusty, and there is quite some rust showing on the rim as well. The front ones are in better shape comparatively but not worth salvaging if replacements are affordable. Back to work in 8 hours, so I'll get the tires off and take a look tomorrow night for the rusting form the inside. I really hope the head gets here soon, want to work on the engine first :D :D

Offline edwardmorris

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #255 on: January 10, 2014, 08:28:00 PM »
OK, in between shifts today so took a quick peek at the rear wheel. The tire reads 13/90-17 but the rim diameter when I measure shows 18" and the hub diameter is 8". Is this the right spec for a K2? I hope its just a wrong tire on the right rim and not the whole assembly. If the rim and hub diameters are good I won't have to hunt down yet another thing. The spoke length is 5". Please someone post that this is correct :) :)

Offline MCRider

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #256 on: January 10, 2014, 08:33:25 PM »
OK, in between shifts today so took a quick peek at the rear wheel. The tire reads 13/90-17 but the rim diameter when I measure shows 18" and the hub diameter is 8". Is this the right spec for a K2? I hope its just a wrong tire on the right rim and not the whole assembly. If the rim and hub diameters are good I won't have to hunt down yet another thing. The spoke length is 5". Please someone post that this is correct :) :)
The stocker was a 120+/- /90-18. (4.00/18 actually in inches) No way someone levered a 17" tire onto an 18" rim. So you either measured wrong, or read the size wrong.

A 130/90-18 tire would fit on a stock rim, technically a skosh too wide.

Some have converted K2 wheels to K7/8 wheel which were 17" rims.
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1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
"Sometimes the light's all shining on me, other times I can barely see, lately it appears to me, what a long, strange trip its been."

Offline edwardmorris

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #257 on: January 10, 2014, 08:57:59 PM »
Here are some pics, at this point I'd rather get a new rim instead of trying to find a hub. If this hub will work with a proper 18" rim I'd rather go that way, but if the hub itself is the wrong size, then yet another PO fail.

Probably the worst way to measure but I gotta run, hope to get some good news when I check back

Offline edwardmorris

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #258 on: January 10, 2014, 08:58:45 PM »
Spoke and tire

Offline Trevdawg

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #259 on: January 10, 2014, 10:35:42 PM »
Definitely have to take some time and look over all these pages.  Looks interesting

Offline Terry in Australia

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #260 on: January 10, 2014, 11:39:36 PM »
Yeah, you've got a 17 inch rim Ed, as Ron mentioned, it might be off a K7 or K8, but you should have an 18 inch rear rim on your K2. That hub will work fine with an 18 inch rim though, so just buy a new rim and spokes. Cheers, Terry. ;D
I was feeling sorry for myself because I couldn't afford new bike boots, until I met a man with no legs.

So I said, "Hey mate, you haven't got any bike boots you don't need, do you?"

"Crazy is a very misunderstood term, it's a fine line that some of us can lean over and still keep our balance" (thanks RB550Four)

Offline MCRider

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #261 on: January 11, 2014, 06:19:30 AM »
Yeah, 17". I don't know all the ins and outs of the conversion. Many here have done it. You have to swap drive plates and bits.

The rim measurement is from the bottom of the bead on each side, not the top, furthest most edges. You have to guess a little bit but essentially, don't include the outermost flat area of the rim ini your measurements. See thru the rim to where the bead of the tire is, with XRay vision, and measure from there.
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1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
"Sometimes the light's all shining on me, other times I can barely see, lately it appears to me, what a long, strange trip its been."

Offline edwardmorris

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #262 on: January 11, 2014, 10:33:28 AM »
Thanks Terry and Ron, I'm so glad the hub will work! So for my upcoming birthday, should I get me two sets of stainless spokes? Or would you recommend something else?

Telescoping gauges from Gordon came in today, too worked up to go to bed so I took the measurements parallel and perpendicular to the pins as requested :D I really hope I did this right, here are the numbers (upper and lower ends)

Cylider#1#2#3#4
PerpendicularU60.94 L60.93U60.95 L60.95U60.94 L60.95U60.95 L60.95
ParallelU60.93 L60.94U60.93 L60.93U60.93 L60.92U60.92 L60.92

Hone or rebore? Or redo measurements? I'll go read the manual while I try to catch some zzzs
« Last Edit: January 11, 2014, 02:07:08 PM by edwardmorris »

Offline MCRider

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #263 on: January 11, 2014, 11:36:48 AM »
I'll just comment on the wheel/rim issue. Bores are above my pay grade.  :D

The standard upgrade is oversize stainless from Buchanan's. But stock spokes (for an 18) Or stock size stainless.

Depends a bit on the rim you want to use. A stock 18" rim will not (may not) allow for the bigger nipples and OEM is your choice. A aftermarket aluminum rim can be drilled to fit the oversize spoke nipples if desired.
Ride Safe:
Ron
1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
"Sometimes the light's all shining on me, other times I can barely see, lately it appears to me, what a long, strange trip its been."

Offline Terry in Australia

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #264 on: January 11, 2014, 01:57:02 PM »
Your measurements look about right Ed, except the second last one, did you mean 60.92? 60.02 isn't right. they're all pretty uniform though, so as long as there's no obvious gouging evident, a hone will do the job fine.

I like fatter spokes on a hotrod CB750, I've got Ron's old Borrani rim and Buchanans (?) fat stainless spokes on the front of my bike and love the look, but I can't see any reason to go with fatter spokes on an otherwise stock bike, the OEM sizes are adequate for normal riding. Cheers, terry. ;D 
I was feeling sorry for myself because I couldn't afford new bike boots, until I met a man with no legs.

So I said, "Hey mate, you haven't got any bike boots you don't need, do you?"

"Crazy is a very misunderstood term, it's a fine line that some of us can lean over and still keep our balance" (thanks RB550Four)

Offline edwardmorris

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #265 on: January 11, 2014, 02:12:50 PM »
Oops, that was a typo, fixed now :) Looked at the manual and looks like I'm just under, hopefully honing won't push it right on the edge.

As for the rim and spokes, I was thinking about this rim with these spokes. Are these overkill?

Offline Terry in Australia

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #266 on: January 11, 2014, 02:20:56 PM »
I like the rim and have dealt with that seller before, they're good. I don't like the spoke nipples though, with the phillips screwdriver slots? The OEM nipples have straight slots, which I think would be easier to lace. Does the rim seller do spokes too? Cheers, Terry. ;D
I was feeling sorry for myself because I couldn't afford new bike boots, until I met a man with no legs.

So I said, "Hey mate, you haven't got any bike boots you don't need, do you?"

"Crazy is a very misunderstood term, it's a fine line that some of us can lean over and still keep our balance" (thanks RB550Four)

Offline edwardmorris

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #267 on: January 11, 2014, 06:09:24 PM »
The seller only has the front set NOS listed for more than the rim itself  :o I'll do some digging for a good replacement set with the DID rim.

Woke up and the mail was here! Head came in so I got right to work, springs are painfully strong and valves all passed the drill motor test, but have all kinds of crap on them, maybe even RUST?? The guides on the exhaust side are seal-less, but cruddy, not sure what that brown stuff is. How would this rust if the bike was running?

Offline BPellerine

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #268 on: January 11, 2014, 06:23:01 PM »
that may be just some deposit from age it should clean up great.sometimes things can rust a little if the bike was only run for short periods and then left to sit ie condensation.bill
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Offline edwardmorris

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #269 on: January 12, 2014, 10:16:58 PM »
Looongass day today, made some time to start cleaning the head, there is severe carbon built up in the exhaust ports, hit metal after almost an hour of scrubbing, and its as if there are bubbles in it, so rough no wonder everything is sticking to it. Any tips on speeding up cleaning?

Offline BPellerine

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #270 on: January 13, 2014, 12:33:14 PM »
dremel and wire wheel.bill
1978 CB 750K ard and webers
another anfob

Offline edwardmorris

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #271 on: January 13, 2014, 09:27:58 PM »
Here is how the ports are now. Tips, suggestions, advice on how to proceed? I'm nowhere near done cleaning the head, but it looks nice enough to share

#
4-3
2-1
4

on the exhaust side
« Last Edit: January 13, 2014, 09:29:35 PM by edwardmorris »

Offline edwardmorris

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #272 on: January 13, 2014, 09:31:46 PM »
3, 2, 1

why do I always take these wrong side up?

Offline edwardmorris

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #273 on: January 13, 2014, 09:34:12 PM »
intake side
#
4-3
2-1
4

Offline edwardmorris

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #274 on: January 13, 2014, 09:35:41 PM »
3,2,1 inlet