Author Topic: Beautiful 1972 cb750 with dagnabbit stuck engine  (Read 20451 times)

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Offline Hondawggie

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Beautiful 1972 cb750 with dagnabbit stuck engine
« on: October 29, 2011, 08:51:32 AM »
I've been here before trying to unstick a 4/4 bike engine.  I have re-applied ATF+acetone for a few days and she won't break free.


I know from experience on another bike you cannot put a breaker bar on the points side so my question is -- can I remove the *left* side engine cover and be able to get enough leverage to turn the crank?  Getting tired of rockin' back-n-forth every day.   

I put her in 5th gear and rock back-n-forth.    I freed one up 2 years back by having it up on the center stand then climbing aboard and forcing it to drop forward off the center stand -- but that trick doesn't work with this one.

THIS BABY HAS only 5k ORIGINAL MILES.  1972 cb750, still has the factory stock tires!  Man-oh-man.  Seat and tank look new, oh the garage neglect on this one.  I have never owned a 1972 with such low miles.

Offline MCRider

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Re: Beautiful 1972 cb750 with dagnabbit stuck engine
« Reply #1 on: October 29, 2011, 09:00:43 AM »
The rotor bolt under the alternator cover can take almost all you can give it. Turning the engine forward though will tend to loosen the bolt. So it may break free before the engine does. Should be about 70ft lbs, IIRC

Turning the engine in reverse with that bolt will tend to tighten the bolt and in that direction, something will have to give, with a big enough cheater bar. never seen it, but you'd have to suspect 100+ ft/lbs might break the bolt or the crank.

Tilt the bike to the right to get the bit of oil in that cover to drain to the sump. Use a drip pan anyway.
« Last Edit: October 29, 2011, 09:02:23 AM by MCRider »
Ride Safe:
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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 Elpresidente

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Re: Beautiful 1972 cb750 with dagnabbit stuck engine
« Reply #2 on: October 29, 2011, 09:10:25 AM »
Pictures or it didn't happen!  ;D
'73 CB500
'12 Triumph Thruxton

Offline Hondawggie

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Re: Beautiful 1972 cb750 with dagnabbit stuck engine
« Reply #3 on: October 29, 2011, 09:46:14 AM »
Pictures or it didn't happen!  ;D

I have the easy-to-remove pieces off for de-dusting/cleaning and heres the cleaned up tank.




Years of dust on this bike.  I have never owned a cb750 with the original tires on it.  I have no plans to replace anything on the bike -- it is only original once.   For example you can see patina on  some bits of it.   But I have to figure out if I want to revive it.

Offline Tews19

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Re: Beautiful 1972 cb750 with dagnabbit stuck engine
« Reply #4 on: October 29, 2011, 11:24:06 AM »
Interesting.
1969 Honda CB750... Basket case
1970 Honda CB750 survivor.

Offline d9canada

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Re: Beautiful 1972 cb750 with dagnabbit stuck engine
« Reply #5 on: October 29, 2011, 11:48:38 AM »
I would use diesel, it penetrates like mad and lubes.  I have seen a very extreme example of a Merc outboard that got dunked in salt water then left in storage for a couple years.  It was growing hair.  Now, bear in mind that the mechanic was stripping the beast.  But to get the pistons freed, he used Coke Classic.  Remember in school when the science teacher would put a nail in a cup of coke and the next day the nail had dissolved?  Well...  In about a half hour the pistons were moving, albeit with a fair bit of force.

If your bike is so stuck, personally I would pull the motor because I would not free it up and try to run it.  It likely will have damage to the bores that your rings will be clanging over for a while til something rubs off or something breaks.  It needs at least a hone, best to do the rings at the same time.

Most likely your carbs could use a clean-up too.  Here's a good carb guide:
http://www.salocal.com/sohc/tech/tech.htm

So you have the tank off, flush it and get an inline filter, do the carbs, then yank the stove and fix it properly, or you may have a pretty bike that was stuck, got unstuck and then blew.
Brian

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64 Suzuki M15D Sovereign 50cc

Offline dave500

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Re: Beautiful 1972 cb750 with dagnabbit stuck engine
« Reply #6 on: October 29, 2011, 12:31:12 PM »
great colour,unbelievable butter.

Offline Tews19

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Re: Beautiful 1972 cb750 with dagnabbit stuck engine
« Reply #7 on: October 29, 2011, 12:54:53 PM »
Wow....that tank is cleaner than your wife's stove there... ;D


 ;)
1969 Honda CB750... Basket case
1970 Honda CB750 survivor.

Offline BobbyR

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Re: Beautiful 1972 cb750 with dagnabbit stuck engine
« Reply #8 on: October 29, 2011, 12:55:20 PM »
The Acetone evaporates very quickly, so you may need multiple applications. Diesel is Kerosene and that works OK too.  The rocking it in gear may be your best bet.

When you do get this running, I would not ride on original tires. You can store them but riding on them is insane.
Dedicated to Sgt. Howard Bruckner 1950 - 1969. KIA LONG KHANH.

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Offline d9canada

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Re: Beautiful 1972 cb750 with dagnabbit stuck engine
« Reply #9 on: October 29, 2011, 01:09:29 PM »
Minor correction:

Diesel (a more refined version of heating oil) is NOT kerosene (aka coal oil) which is most often used these days as an aircraft fuel.

Good call on tires.  3 years is the general rule, 5 is pretty much max.
Brian

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Offline Hush

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Re: Beautiful 1972 cb750 with dagnabbit stuck engine
« Reply #10 on: October 29, 2011, 01:30:56 PM »
Nice find, I'm with d9canada, you could have a mint bike here but the motor needs some love even if you unstick it without snapping the rings.
If you take the head off it will be easier to unstick the pistons as you can see where the lube is going, it will cost you a head gasket set but since the bike is so primo it would be a shame to half -ass it, nice find.
I think the thing I most like about motorcycling is the speed at which my brain must process information at to avoid the numb skulls who are eating pies, playing the ukulele, applying make-up etc in the comfort of their airconditioned armchairs as they make random attempts to kill me!!!!!!!

Offline Hondawggie

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Re: Beautiful 1972 cb750 with dagnabbit stuck engine
« Reply #11 on: October 29, 2011, 02:09:50 PM »
Wow....that tank is cleaner than your wife's stove there... ;D

The wifes job (cover you wifes ears on this) the wifes job is to clean the stove and whatnot.
The Church of Feminism of Latter-Day Wives has them not cleaning the stove.   
And this is a bikers kitchen I have a '92 Zephyr 750 and an '86 Nighthawk 750 gas tanks off to the left,  I have a Kaw H2-750 tank the the floor to the right, I have 3 sets of chambers for a 750 and 400 Kaw triples, I have 3 sets of RD-400 pipes leaned up against the kitchen sink, I have a first-year cb500-four set of stock pipes leaned against the wall in the shower, right next to a full set of HM341's that will be cleaned *inside the recently remodeled bathroom shower* directly.

The thing a wife does NOT know is how relatively easy it is to clean off various oils and grease from recently-painted walls.  Now in the bedroom I have a set of Z1 carbs, a full set of 1986 gsxr 750 original fairings, gas tank from a Yamaha Daytona RD400 ready for cleaning.   

The Church of Feminism of Latter-Day Wives  will not tolerate this type of bikerdom, generally.  Thankfully I took up dating again after waving 'good bye' one last time to the ex.


Key take away on the 'Unbelievable Butter' popcorn there -- that was me being generous, a group of Brownies (these are the younger version of the Girl Scouts, the Brownies if you remember that far back were akin to the Cub Scouts which were the junior version of Boy Scouts) were cornering people outside the grocery store.   I paid the Brownies $18.00 for that box of 'Outrageous Butter' popcorn and someone sold the Brownies' reputation down the river on that deal -- should say "Outrageous *lack of butter, butter-tasting oils, or anything* Butter popcon.  No butter to speak of.  Dry as the sahara.

However I still feel good about overpaying for the bait-and-switch popcorn, goes to a good cause.

Offline Eydugstr

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Re: Beautiful 1972 cb750 with dagnabbit stuck engine
« Reply #12 on: October 29, 2011, 04:34:50 PM »
If your bike is so stuck, personally I would pull the motor because I would not free it up and try to run it.  It likely will have damage to the bores that your rings will be clanging over for a while til something rubs off or something breaks.  It needs at least a hone, best to do the rings at the same time.

Most likely your carbs could use a clean-up too.  Here's a good carb guide:
http://www.salocal.com/sohc/tech/tech.htm

So you have the tank off, flush it and get an inline filter, do the carbs, then yank the stove and fix it properly, or you may have a pretty bike that was stuck, got unstuck and then blew.


+1.  If the rest of the bike looked as good as that tank did in the photo...It's more than worth the money to remove the motor and just rebuild it outright.  Carbs too.  What a find, though!

Offline Hondawggie

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Re: Beautiful 1972 cb750 with dagnabbit stuck engine
« Reply #13 on: October 29, 2011, 05:57:49 PM »
If your bike is so stuck, personally I would pull the motor because I would not free it up and try to run it.  It likely will have damage to the bores that your rings will be clanging over for a while til something rubs off or something breaks.  It needs at least a hone, best to do the rings at the same time.

Most likely your carbs could use a clean-up too.  Here's a good carb guide:
http://www.salocal.com/sohc/tech/tech.htm

So you have the tank off, flush it and get an inline filter, do the carbs, then yank the stove and fix it properly, or you may have a pretty bike that was stuck, got unstuck and then blew.


+1.  If the rest of the bike looked as good as that tank did in the photo...It's more than worth the money to remove the motor and just rebuild it outright.  Carbs too.  What a find, though!

Yep parting it out would help some folks out there but I bought this one with the intent on riding it, so I may take out the motor.  However, the prior owner said 'it was turning over fine a year ago' so that means it will be ready to go once I free her up, if he was being honest with me about the 'turning over fine last year.'  He sold it because he had been neglecting the bike 'for a year.'  I hope he was being truthful.

Thanks everyone for the great tips, I will update with the progress -- I have 2 tricks to bring to bear on this:

1) I'll use the starter button -- the starter I believe has more leverage (?) on the crank that putting the bike in 5th gear and rocking it back and forth.   

2) if that fails to get it turning, I will pull off the left-side engine cover and use a breaker bar on that heavy-duty rotor bolt mentioned above

If the p.o. was being straight with me, one year's worth of cylinder oxidation should not be a big deal.

Offline harisuluv

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Re: Beautiful 1972 cb750 with dagnabbit stuck engine
« Reply #14 on: October 29, 2011, 06:49:48 PM »
That tank is beautiful.  Sunrise Orange is one of my faves.  It really has a brilliance to it.

Offline Stev-o

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Re: Beautiful 1972 cb750 with dagnabbit stuck engine
« Reply #15 on: October 29, 2011, 07:53:15 PM »
I do not think the starter motor will have enough torque to free it. Let it soak for a couple more days.

Nice find and good luck.
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Offline Spanner 1

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Re: Beautiful 1972 cb750 with dagnabbit stuck engine
« Reply #16 on: October 29, 2011, 08:09:41 PM »
Fake post  ;)... no picture of the bike , lots of blah, blah about Girl Scouts, Kawasakis, cookies... pic of a tank... great !... where's the beef ?
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If your sure it's an ignition problem; it's carbs....

Offline d9canada

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Re: Beautiful 1972 cb750 with dagnabbit stuck engine
« Reply #17 on: October 29, 2011, 08:36:08 PM »
If the PO was being straight with you about the bike turning fine a year ago, it would not be locked so solidly now.  Neither the rotor bolt nor the starter is as robust a connection than 5th gear through the drivetrain that was made to take full power. 

I'm glad you won't part it out, there's too much of that.
Brian

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64 Suzuki M15D Sovereign 50cc

Offline ekpent

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Re: Beautiful 1972 cb750 with dagnabbit stuck engine
« Reply #18 on: October 29, 2011, 09:36:13 PM »
Here is a pic of my old Kaw 400 with the side cover off that I rode this summer in the rough-show me yours please-Been buying some old smokers this summer,Kaws,Suzuki triples,RD350's etc.Got a orange 72 if you want to see a pic of that also.Hope you get it unstuck,sounds nice.
« Last Edit: October 29, 2011, 09:42:51 PM by ekpent »

Offline Spanner 1

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Re: Beautiful 1972 cb750 with dagnabbit stuck engine
« Reply #19 on: October 29, 2011, 09:57:16 PM »
Where's the beef.... a tank, lovely... your camera can't take a pic. of the bike your 'ranting' about , only7,000 miles' etc., whatever :(... but I'll talk about the ' church of feminism of latter day wives' WTF ). Take more meds  ;D
If your sure it's a carb problem; it's ignition,
If your sure it's an ignition problem; it's carbs....

Offline ekpent

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Re: Beautiful 1972 cb750 with dagnabbit stuck engine
« Reply #20 on: October 29, 2011, 10:05:44 PM »
As Spanner has mentioned and I have shown pics are easy to post and we really like to see what our fellow members are dealing with.

Offline Hondawggie

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Re: Beautiful 1972 cb750 with dagnabbit stuck engine
« Reply #21 on: October 29, 2011, 11:14:54 PM »
Fake post  ;)... no picture of the bike , lots of blah, blah about Girl Scouts, Kawasakis, cookies... pic of a tank... great !... where's the beef ?
ouch, the dang bike's under a tarp.  Besides, it was an overpriced and under-buttered eighteen-dollar box of *popcorn* not cookies, I will not pay $18 for a box of them cookies I already have a dentist visit for much needed repairs on my lower right molars, if Groupon had not come along and coerced this dentist to give away his services I would not have known to stop eating sugary foods.  Eighteen-dollar popcorn -- sugar free.

I dont know about this bike.  Pulling the motor might lead to 'parting out'.  Once you get something apart in a big way and you find out the current market value of a restored '72 is $2650 (per ebay) you start to wonder about stuff.    http://cgi.ebay.com/ebaymotors/1971-Honda-CB750-Candy-Gold-Restored-/120796830078?pt=US_motorcycles&hash=item1c200d597e

Offline Hondawggie

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Re: Beautiful 1972 cb750 with dagnabbit stuck engine
« Reply #22 on: October 29, 2011, 11:20:58 PM »
Here is a pic of my old Kaw 400 with the side cover off that I rode this summer in the rough-show me yours please-Been buying some old smokers this summer,Kaws,Suzuki triples,RD350's etc.Got a orange 72 if you want to see a pic of that also.Hope you get it unstuck,sounds nice.

well the seat and tank are off for cleaning first, I got the tank done, next comes the seat.   I have no plans to clean the rest of the bike.   Not yet anyway.  I always put off cleaning until the end.   So be patient I will not show the souls of my feet unless they are clean and/or/there are no Muslims in the area.  Along with that I need to get the mechanical stuff on this bike going before I'll put the cleaned tank on, put the cleaned seat on, the cleaned bike then shoot it.  THEN you will be overwhelmed, it WILL be worth waiting for.    After seeing that $2650 ebay auction for a restored '71 I may part this out and not mess with it.

Offline Retro Rocket

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Re: Beautiful 1972 cb750 with dagnabbit stuck engine
« Reply #23 on: October 29, 2011, 11:24:57 PM »
That gold bike on ebay is worth more than 2600 mate, it didn't sell, it also won't cost you that much to fix the engine. DON'T part it out, its a surviver in great condition, if its too much for you too fix then sell it complete. If it has as little mileage as you say and was running 12 months ago then it can't be that bad, have some patience it will come unstuck.....
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Offline Hondawggie

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Re: Beautiful 1972 cb750 with dagnabbit stuck engine
« Reply #24 on: October 29, 2011, 11:28:27 PM »
If the PO was being straight with you about the bike turning fine a year ago, it would not be locked so solidly now.  Neither the rotor bolt nor the starter is as robust a connection than 5th gear through the drivetrain that was made to take full power. 

I'm glad you won't part it out, there's too much of that.

Bummer to hear that.  Bummer.  The last time it was registered was in the late 80s.  If he did lie to me it could have been sitting stuck for somewhere around 20 years then.   This will be the 3rd time over these years I trusted someone on a stuck motor and 'how long its been.'   I hope it comes free.   I hope he was being honest about it turning over last year.