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Online grcamna2

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Re: Help with new CB650 Project
« Reply #25 on: November 29, 2023, 10:46:27 PM »
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75' CB400F/'bunch o' parts' & 81' CB125S modded to a 'CB200S'
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Offline newday777

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Re: Help with new CB650 Project
« Reply #26 on: November 30, 2023, 12:02:43 AM »
Quote from: calj737 on November 29, 2023, 05:44:32 PM
Slow down. You’re all over the place.

The crack in the case is the indication your issue is with the starter clutch. You can remove the cam chain without cutting it by rotating the crank to access the 2 bolts holding the cam sprocket to the camshaft. Once you’ve done that, release the tension and slightly raise the chain straight up, then slip the cam to the left to clear the sprocket.

Before removing the camshaft, tie up your cam chain with some zip ties to prevent it falling into the cavity.

Then you can start removing the oil pan and looking up to understand more of the damage.

You can’t buy “cases” unless the bearings match your crankshaft. But whole cases as a matched set (or another motor) are in your future. Sorry about your bad luck  :-\
His motor is seized. He can't rotate the crank or the cam.
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Stu
Honda Parts manager in the mid 1970s Nashua Honda
My current rides
1975 K5 Planet Blue my summer ride, it was a friend's bike I worked with at the Honda shop in 76, lots of fun to be on it again
1976 K6 Anteres Red rebuilding project, was originally my brother's that I set up from the crate, it'll breath again soon!
Project 750s, 2 K4, 2 K6, 1 K8
2008 GL1800 my daily ride and cross country runner

Prior bikes....
1972 Suzuki GT380 I had charge of it for a year in 1973 while my friend was deployed and learned to love street riding....
New CB450 K7 after my friend returned...
New CB750 K5 Planet Blue, demise by ex cousin in law at 9,000 miles...
New CB750 K6 Anteres Red, to replace the totaled K5, I sold this K6 at 45k in 1983, I had heavily modified it, many great memories on it and have missed it greatly.....
1983 GL1100A, 1999 GL1500 SE, 1999 GL1500A

Offline newday777

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Re: Help with new CB650 Project
« Reply #27 on: November 30, 2023, 12:04:58 AM »
Quote from: 76 Supersport on November 29, 2023, 03:26:27 PM
I guess my question is, now what?

If it was sitting in your garage what would you do with it? I’ve got more time than money and don’t mind a project.


Get another motor, another donor bike.....
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Stu
Honda Parts manager in the mid 1970s Nashua Honda
My current rides
1975 K5 Planet Blue my summer ride, it was a friend's bike I worked with at the Honda shop in 76, lots of fun to be on it again
1976 K6 Anteres Red rebuilding project, was originally my brother's that I set up from the crate, it'll breath again soon!
Project 750s, 2 K4, 2 K6, 1 K8
2008 GL1800 my daily ride and cross country runner

Prior bikes....
1972 Suzuki GT380 I had charge of it for a year in 1973 while my friend was deployed and learned to love street riding....
New CB450 K7 after my friend returned...
New CB750 K5 Planet Blue, demise by ex cousin in law at 9,000 miles...
New CB750 K6 Anteres Red, to replace the totaled K5, I sold this K6 at 45k in 1983, I had heavily modified it, many great memories on it and have missed it greatly.....
1983 GL1100A, 1999 GL1500 SE, 1999 GL1500A

Offline calj737

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Re: Help with new CB650 Project
« Reply #28 on: November 30, 2023, 06:16:05 AM »
Quote from: Tracksnblades1 on November 29, 2023, 07:53:18 PM
Something wanted out. If it wanted out at 10,000 rpm, it won’t be good…
It wouldn’t even need to be at 10k RPMs. 2-3k is plenty of inertia to trash a motor. If the underside of the cylinder head is undamaged, then it wasn’t a rod that let go. But a full teardown is required to adequately diagnose and repair that motor (if doable).
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"Of all tyrannies, a tyranny sincerely exercised for the good of it's victim may be the most oppressive. It may be better to live under robber barons than under omnipotent moral busybodies. The robber baron's cruelty may sometimes sleep, his cupidity may at some point be satiated, but those who torment us for our own good will torment us without end for they do so with the approval of their own conscience." - C.S. Lewis

Offline bryanj

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Re: Help with new CB650 Project
« Reply #29 on: November 30, 2023, 08:41:48 AM »
With the engine out and side cases removed along with all the clutch and gearchange parts you can separate the lower crancase to find whats exploded and probably unjam the crank to rotate and strip out cam, head and cylinders.
In the end a different engine will probably be cheapest option BUT if you strip this one first and top end is good you could look for just a bottom end which may be cheaper
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Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

Remember "Its always in the last place you look" COURSE IT IS YOU STOP LOOKIN THEN!

Offline fizzlebottom

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Re: Help with new CB650 Project
« Reply #30 on: November 30, 2023, 09:53:06 AM »
If I were in your shoes, I probably wouldn't bother tearing this thing apart and doing any repairs. I would sit on eBay and wait for a reasonable motor to pop up. I already did this a few years ago and my eBay motor has been running perfectly since then.

Here's my reasoning: Whatever blew the hole in the case also threw debris all over the internals. If that debris clogged up any oil passages, you may have burned up bearings. If that debris got into the bearings before clogging up oil passages, you may have burned up bearings. If that debris got up to the cylinder walls then you may have to overbore. Boring and pistons aren't a big deal, but bearings sure can be. Especially crankshaft bearings, because they're nearly impossible to find for the CB650 motors. If the camshaft bearing surfaces are messed up, game over until you replace the cylinder head cover.

Add up all of the time and money on both parts & work sent out to shops and you may be paying for a new motor. It is a risk to go down that rabbit hole, and also a risk to buy a used motor. But I'd rather start with a complete cosmetically undamaged motor that spins to work with instead of one that needs critical repairs off the bat.

Others may disagree, but that's my take.
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Offline bryanj

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Re: Help with new CB650 Project
« Reply #31 on: November 30, 2023, 11:10:56 AM »
I agree, but the mechanic in me wants to know exactly what went bang
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Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

Remember "Its always in the last place you look" COURSE IT IS YOU STOP LOOKIN THEN!

Offline 76 Supersport

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Re: Help with new CB650 Project
« Reply #32 on: November 30, 2023, 01:53:03 PM »
Ta-da! (See attached pictures)
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Offline 76 Supersport

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Re: Help with new CB650 Project
« Reply #33 on: November 30, 2023, 01:55:21 PM »
Although I want to feel special (first time anyones seen a primary chain break) I think the chain is the chicken and not the egg here.
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Offline newday777

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Re: Help with new CB650 Project
« Reply #34 on: November 30, 2023, 02:16:30 PM »
That tensioner doesn't look so healthy either. Can you spin the motor any now to access the cam sprocket bolts?
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Stu
Honda Parts manager in the mid 1970s Nashua Honda
My current rides
1975 K5 Planet Blue my summer ride, it was a friend's bike I worked with at the Honda shop in 76, lots of fun to be on it again
1976 K6 Anteres Red rebuilding project, was originally my brother's that I set up from the crate, it'll breath again soon!
Project 750s, 2 K4, 2 K6, 1 K8
2008 GL1800 my daily ride and cross country runner

Prior bikes....
1972 Suzuki GT380 I had charge of it for a year in 1973 while my friend was deployed and learned to love street riding....
New CB450 K7 after my friend returned...
New CB750 K5 Planet Blue, demise by ex cousin in law at 9,000 miles...
New CB750 K6 Anteres Red, to replace the totaled K5, I sold this K6 at 45k in 1983, I had heavily modified it, many great memories on it and have missed it greatly.....
1983 GL1100A, 1999 GL1500 SE, 1999 GL1500A

Offline Tracksnblades1

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Re: Help with new CB650 Project
« Reply #35 on: November 30, 2023, 02:33:36 PM »
Quote from: calj737 on November 30, 2023, 06:16:05 AM
Quote from: Tracksnblades1 on November 29, 2023, 07:53:18 PM
Something wanted out. If it wanted out at 10,000 rpm, it won’t be good…
It wouldn’t even need to be at 10k RPMs. 2-3k is plenty of inertia to trash a motor. If the underside of the cylinder head is undamaged, then it wasn’t a rod that let go. But a full teardown is required to adequately diagnose and repair that motor (if doable).

Agree…..

But centrifugal forces square as the rpm goes up….Too bad the photos  aren’t good enough for “the rest of the story…

I’m betting the max rpm for the 650’s  Hyvo chain isn’t much above its tachometer’s redline..Ramsey Chain has all the engineering specs for the Morse type Hyvos.  Limiting High Rpm centrifugal forces usually exceed the tensile strength of the chain…

Bear, the wizard from Oz, has mentioned his findings Dohc Hyvos in Sohc strokers’ limiting his engine’s rpms. Even with frequent regimented inspection and tear down schedules  the Hyvo chain was the fuse…

Im thinking the cb350 had the highest redline of the sohc hyvo’s….

Looks like Bryan J hit the nail on the head…with the cracks high and low I knew it wasn’t going to be an economical fix..
I still don’t think we know the real story….

« Last Edit: November 30, 2023, 02:46:19 PM by Tracksnblades1 »
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Offline 76 Supersport

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Re: Help with new CB650 Project
« Reply #36 on: November 30, 2023, 02:39:06 PM »
Everything I could get out. Going to try and rotate motor.
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Offline Tracksnblades1

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Re: Help with new CB650 Project
« Reply #37 on: November 30, 2023, 02:49:33 PM »
Quote from: 76 Supersport on November 30, 2023, 02:39:06 PM
Everything I could get out. Going to try and rotate motor.

Bet it made that oh so familiar but disappointing “Shuuunnk” sound when it wanted out…
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Offline 76 Supersport

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Re: Help with new CB650 Project
« Reply #38 on: November 30, 2023, 03:05:06 PM »
Still not budging. So clutch and everything out of the transmission, then try and get some case halve separation? Is there anything that I should do while the motors still in the bike? I.E. crack head bolts


Here are a couple horrible pictures from under the bike.
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Offline 76 Supersport

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Re: Help with new CB650 Project
« Reply #39 on: November 30, 2023, 03:22:53 PM »
We’ll I’m humbled again.. as the worlds biggest dumbass I think I have found the rest of the story..

See pictures…


Second picture is the screen to my borescope it appears to be an (end cap?) wedged between the crank and rod arm.
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Offline calj737

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Re: Help with new CB650 Project
« Reply #40 on: November 30, 2023, 03:40:28 PM »
There’s not a lot of reason to disassemble that motor any further. It has suffered a catastrophic event and is beyond repair. Sh!tty that the PO didn’t disclose the truth or you didn’t get a chance to investigate more fully the condition of the motor.

Good news is: you “can” replace the motor pretty easily with another 79-82 650 motor. The carbs differ between the 80/81 motors so bear that in mind. Another option is a 500 or 550 motor will bolt in. You’d lose some power based upon stock specs, and the 500 has a slightly different RR motor hangar because the clutch is on the left side. (Just listing options).

If you want a storm trooper of a motor, I have a full tilt 500 that is an over the top motor you could plug in. It will make more HP than the stock 650 by a good bit.

All in all, a crappy way to get started in your first SOHC.  :(
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'74 550 Build http://forums.sohc4.net/index.php?topic=126401.0
'73 500 Build http://forums.sohc4.net/index.php?topic=132935.0

"Of all tyrannies, a tyranny sincerely exercised for the good of it's victim may be the most oppressive. It may be better to live under robber barons than under omnipotent moral busybodies. The robber baron's cruelty may sometimes sleep, his cupidity may at some point be satiated, but those who torment us for our own good will torment us without end for they do so with the approval of their own conscience." - C.S. Lewis

Offline 76 Supersport

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Re: Help with new CB650 Project
« Reply #41 on: November 30, 2023, 06:23:02 PM »
Thank you for the advice. On the bright side with the starter off and the stator off there’s only three bolts left to drop the motor.

What’s a good price for a 650 motor? I see some in the  5 to 7 hundred range on eBay.
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Offline Tracksnblades1

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Re: Help with new CB650 Project
« Reply #42 on: November 30, 2023, 07:10:58 PM »
Quote from: 76 Supersport on November 30, 2023, 06:23:02 PM
Thank you for the advice. On the bright side with the starter off and the stator off there’s only three bolts left to drop the motor.

What’s a good price for a 650 motor? I see some in the  5 to 7 hundred range on eBay.

I was wondering if that was what wanted out.. Especially reading the head and the cases were broke..At least you know “the rest of the story”. And what caused the Hyvo chain failure.

One would believe the rider would of heard a warning…but sometimes all you get to hear is that dreadful shhuunnk…

Good you found your issues… Perhaps you can hear the donor bike run prior to the purchase …Good Luck…
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Online grcamna2

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Re: Help with new CB650 Project
« Reply #43 on: November 30, 2023, 07:59:17 PM »
Quote from: 76 Supersport on November 30, 2023, 06:23:02 PM
Thank you for the advice. On the bright side with the starter off and the stator off there’s only three bolts left to drop the motor.

What’s a good price for a 650 motor? I see some in the  5 to 7 hundred range on eBay.

You may find a very good deal on an 82' CB650 (sohc) Nighthawk complete bike over the Winter;a person may have one and 'word of mouth' you find out they just 'want it gone'.
I would imagine you could verify the engine's 'free' (not seized)by putting the bike up on the centerstand and putting it in 5th gear and turning the back wheel,even if it's presently not running.

Honda came out with the 83' CB650SC Nighthawk in 83' and everyone forgot about the earlier SOHC 650 Nighthawk in favor of the 83-85' models;deals can be found.
« Last Edit: November 30, 2023, 08:03:48 PM by grcamna2 »
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75' CB400F/'bunch o' parts' & 81' CB125S modded to a 'CB200S'
  I love the small ones too !
Do your BEST...nobody can take that away from you.

Offline fizzlebottom

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Re: Help with new CB650 Project
« Reply #44 on: December 01, 2023, 02:51:56 PM »
Quote from: 76 Supersport on November 30, 2023, 06:23:02 PM
Thank you for the advice. On the bright side with the starter off and the stator off there’s only three bolts left to drop the motor.

What’s a good price for a 650 motor? I see some in the  5 to 7 hundred range on eBay.

I paid $600 after shipping for mine and felt like it was a fair price.
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Offline 76 Supersport

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Re: Help with new CB650 Project
« Reply #45 on: December 01, 2023, 06:21:48 PM »
Found a couple eBay listings. What do you think shipping will be from east - Mid East to California? 2-300?
Messaged both sellers for a Quote so I guess we shall see.

https://www.ebay.com/itm/325366629610?hash=item4bc15cc4ea:g:0GoAAOSw11RjJQW~

https://www.ebay.com/itm/235041491259?campid=5338992317&mkevt=1&mkcid=1&toolid=10050&customid=&mkrid=711-53200-19255-0&campid=5338992317&mkevt=1&mkcid=1&toolid=10050&customid=50b0f978b81e16cec1799c12307c009a&mkrid=710-53481-19255-0&msclkid=50b0f978b81e16cec1799c12307c009a

Compression on second engine looks a little funky, what do y’all think?
« Last Edit: December 01, 2023, 06:25:45 PM by 76 Supersport »
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Online grcamna2

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Re: Help with new CB650 Project
« Reply #46 on: December 01, 2023, 07:40:23 PM »
The first engine in Romeo,MI. looks like the seller is being fair,imo.
You might see if you can work out something to get it shipped/delivered to a local(to you) business loading dock;or possibly Uship.com to your area.
« Last Edit: December 01, 2023, 07:43:23 PM by grcamna2 »
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75' CB400F/'bunch o' parts' & 81' CB125S modded to a 'CB200S'
  I love the small ones too !
Do your BEST...nobody can take that away from you.

Offline 76 Supersport

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Re: Help with new CB650 Project
« Reply #47 on: December 04, 2023, 04:55:08 PM »
What do you all think broke first? See pictures.
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Online grcamna2

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Re: Help with new CB650 Project
« Reply #48 on: December 04, 2023, 04:59:27 PM »
I'm guessing seized piston..
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75' CB400F/'bunch o' parts' & 81' CB125S modded to a 'CB200S'
  I love the small ones too !
Do your BEST...nobody can take that away from you.

Offline Tracksnblades1

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Re: Help with new CB650 Project
« Reply #49 on: December 04, 2023, 05:02:16 PM »
Yep, “the rest of the story”…

That previous owner or someone had to hear that before the light lay over before it seized…🤔

Like Bryan j mentioned about the Hyvo breaking, now you know what broke it…

Was the rod journal that it came from blue..?

 Did you find an engine…? 
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