Author Topic: 1972 CB750 Four K2 -- Rebuilt to NEW OLD STOCK -- PIX ON PAGE 50  (Read 248064 times)

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Offline MCRider

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #225 on: January 05, 2014, 09:03:05 PM »
Nice! Perfect timing Gordon, the crank and the rods are next on the removal, cleaning and inspection list and the rotor is still on, thanks!.

I can get the bore measurements if I can get those specialty tools. The pistons themselves I measured earlier for Terry with a caliper and they are the stock size (never bored). Honing was on my list anyway so I guess new rings will work out for the best.  The busted ones are coming in handy to clean the ring lands :D
point of order: the "lands" are the part between the grooves.  You are cleaning the grooves with the broken bits.

Carry on!   ;D

http://www.hastingsmfg.com/ServiceTips/piston.htm
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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 #226 on: January 05, 2014, 09:31:24 PM »
AH I see, thanks! About that pitting on the piston heads, should I sand it out with a fine grit paper and polish it or leave it be?

Offline MCRider

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #227 on: January 05, 2014, 09:39:28 PM »
asking me? never seen anything like the pits. from detonation? I'd say OK to ignore, but I don't really know.

Get some snow? we got about 12" and the wind begins to howl.
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"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 #228 on: January 05, 2014, 10:08:02 PM »
Question was for @all.

A little worried, apparently pitting happens from the acid formed due to water and carbon mixing. Pitting (like I guessed) will increase carbon deposits too, so I'm trying to see if I can get away with polishing them.


And yes, don't know the official numbers but there is about a 4 foot tall mountain blocking my garage from all the winds blowing it around. Front yard looks about 15 inches of snow though, I really need to get me a snow blower. Four shifts of shoveling and it piles right back up. I live in between Lake Michigan and Wolf lake, so double the lake effect snow gets dumped here.
« Last Edit: January 05, 2014, 11:11:09 PM by edwardmorris »

Offline BPellerine

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #229 on: January 06, 2014, 09:49:35 AM »
same here in Canada Edward!bill
1978 CB 750K ard and webers
another anfob

Offline MCRider

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #230 on: January 06, 2014, 11:24:11 AM »
Question was for @all.

A little worried, apparently pitting happens from the acid formed due to water and carbon mixing. Pitting (like I guessed) will increase carbon deposits too, so I'm trying to see if I can get away with polishing them.


And yes, don't know the official numbers but there is about a 4 foot tall mountain blocking my garage from all the winds blowing it around. Front yard looks about 15 inches of snow though, I really need to get me a snow blower. Four shifts of shoveling and it piles right back up. I live in between Lake Michigan and Wolf lake, so double the lake effect snow gets dumped here.

I see. I'd polish them out till you feel good and move on. The water pitting makes sense.

All's closed in Indy, no unnecessary travel allowed. Maybe another day, too. Give an offering to public utilities and fan forced heat.   :D

I had to downsize my snowblower.  Still @ 20" with electric start and self propelled (forward only) it makes amazing short works of the sidewalks. A truck blade does my larger parts, for a fee.   :(
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 edwardmorris

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #231 on: January 06, 2014, 11:39:36 AM »
Looks like sanding IS an option, I'm going to try since mine don't look to be as deep.

http://forums.sohc4.net/index.php?topic=81955.0

Offline MCRider

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #232 on: January 06, 2014, 11:43:18 AM »
Nice search!
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 greenjeans

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #233 on: January 06, 2014, 02:49:44 PM »
I've sanded some piston tops in the past with no ill effects.  Not really taking much material off - I've also polished the tops thinking it would be harder
for the carbon to stick to a polished surface.   I haven't actually torn things apart to see if it had any effect at all.    I usually run so much seafoam and Chevron gas with Techroline that I just assume they stay clean.   One day I'll have to tear things down just to see.
Yep, I'm the kid that figured out how to put things back together...eventually.

Offline edwardmorris

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #234 on: January 06, 2014, 09:48:34 PM »
Nice search!
Its a moody piece of crap, you either find everything or nothing :D

Today was the worst day. Absolutely zero progress today because I was stupid enough to go out and start shoveling. Snow wrapped up at 18 inches and wind chill of -42 F today. My fingers froze through the gloves so bad I think I have some busted capillaries in my finger tips. Can't do crap till they heal a bit. Oh well, guess a rest day isn't so bad. Garage is still inaccessible, no idea how to deal with the four feet mound in front of the man door. Too much for even a snow blower.

Offline Terry in Australia

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #235 on: January 06, 2014, 10:12:59 PM »
G'Day Ed, sorry I haven't replied earlier, I was away visiting my folks for the last few days. Gordon's right, buy new rings and give the cylinders a good hone.

Those main bearings are expensive to replace (around $100.00) but as you've come this far, I can't see the point in you not replacing them, the primary chains, and the cam chain and tensioner assembly. (CB750Supply.com sells the new tensioner assembly for $79.00 which is really cheap, and they look good, I bought two sets and am happy with the quality) http://www.cb750supply.com/products/4/engine/59/cam-chain-cam-chain-tensioners

Your weather is amazing, it must be great there in summer, otherwise I can't think of one good reason why you'd want to live there? I like my beer icy cold, but not frozen solid! 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?"

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Offline edwardmorris

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #236 on: January 06, 2014, 10:35:12 PM »
Hey welcome back Terry! I was thinking the same, I don't want to open this one again so I'm going to make an investment in it. Where do you get the main bearings? Same site? I could swear there was a thread that cb750supply ones weren't that great.

Offline Terry in Australia

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #237 on: January 06, 2014, 11:21:11 PM »
G'Day Ed, I bought my bearing shells, primary chains etc from Yamiya in Japan, they're all OEM Honda items. I've never used "Non OEM" bearings, so can't comment on their quality except to say that I probably wouldn't use them, any really close tolerance items like bearings are best left to the OEM manufacturer, IMHO. 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 #238 on: January 07, 2014, 08:58:21 AM »
Looks like motogrid has them locally for about the same pricing without the hassle of customs paperwork on delivery. Once I am able to go back into the garage, I'll take a closer look for damage. I recall seeing some ridges being scratched in at least one of them, so it seems more than likely I need new ones. I'll need to go read up on plastigauge again.
« Last Edit: January 07, 2014, 09:27:30 AM by edwardmorris »

Offline Kickstart

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #239 on: January 07, 2014, 03:00:14 PM »
I think some of the favorites on this board for OEM parts are:

www.hondabike.com and
http://www.hdlparts.com

There a lot of online places selling OEM parts - definitely compare prices.

I'm a little bit of a hypocrite saying this, but your shells may be fine.  Get some green plastigage from your local NAPA or autoparts store and take some measurements.  If you're on a budget, and they look good, you may want to save a little money (and a whole lot of hassle - IMHO).  That said, I'm not as experienced as others on this board.

Admittedly I'm replacing all of mine, on my build, (even though I really don't need to) but that's because I want to (both for improved performance and more realistically for the learning experience)... and I'm OK throwing some money at my bike.
- Chris
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Offline edwardmorris

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #240 on: January 07, 2014, 03:36:12 PM »
I think some of the favorites on this board for OEM parts are:

www.hondabike.com and
http://www.hdlparts.com

There a lot of online places selling OEM parts - definitely compare prices.

I'm a little bit of a hypocrite saying this, but your shells may be fine.  Get some green plastigage from your local NAPA or autoparts store and take some measurements.  If you're on a budget, and they look good, you may want to save a little money (and a whole lot of hassle - IMHO).  That said, I'm not as experienced as others on this board.

Admittedly I'm replacing all of mine, on my build, (even though I really don't need to) but that's because I want to (both for improved performance and more realistically for the learning experience)... and I'm OK throwing some money at my bike.

Yep, thanks for the hdlparts link, didn't know of that one. Budget is definitely tight, especially losing hours from all the snow nonsense all new year. I do want to get it done right and I know its going to cost me a bit. I can work towards the cost, at the cost of the losing time on the build. I just finished digging my garage out of the snow, and hopefully will be able to get out of the house tomorrow. I'll do the palstigauge test and then decide. From the factory manual, if even one is bad or has something embedded in it deep, the whole set needs replacing! And I'm afraid mine's going to come to that. The crankcase looks like it was never opened, so I believe a change is overdue??

Offline RRRToolSolutions

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #241 on: January 07, 2014, 06:58:22 PM »
Ed, according to Buzz of Dynoman whom I have a lot of respect for, the original factory supplied insert bearings are better than what you can get today. I can't remember exactly why that is, but he encouraged me to check the clearances on every bearing and use what was in spec. Mark, Terry, and others here may can explain this better than me, but before you mix those or lose track of where they came treat the bearings as though you will re-use them. Measure the clearance with plastiguage (available at most good auto parts places) and replace only as necessary. I wound up tearing mine down a 2nd time at only 600 miles and busting my budget with Buzz's help, but only because I grossly under estimated what porting the Honda CB750 head would do for a 40 year old engine. I know you're looking for a stock build, but if your insert bearings are good - reuse them.

Gordon 
Kaws, Hondas, Yamahas, and Suzukis - especially Kaws

Offline edwardmorris

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #242 on: January 07, 2014, 09:25:47 PM »
Thanks Gordon, I'll do the plastigauge check as soon as possible and post back. I haven't removed any yet because they have been locked up in the garage last few days because of the snow. Its supposed to go back to 0C this weekend here so hoping to make some progress, at least on Sunday. So what happened exactly? I was planning on porting the head ( part of the performance on the budget thing), what should I be looking out for?

It was quite the battle, but the Honda snow blower took down the snow mountain today! Will get really busy next few days and catch up on work. My finger tips are better today so I sanded down the pistons. Stuck to the light side of things, didn't wan't to get greedy and sand away half the piston surface. Still have to wet sand with the finest grits and polish them out as smooth as possible. Look better than they did, so I'll take it. All mail has been delayed  two days now, so no sign of the K2 head yet, hopefully it'll get here before the weekend.

Offline RRRToolSolutions

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #243 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 »
Kaws, Hondas, Yamahas, and Suzukis - especially Kaws

Offline Terry in Australia

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #244 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 #245 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 #246 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 #247 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 #248 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 #249 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.
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."