Author Topic: K8 Engine Damage - cam shaft sprocket in pieces  (Read 9301 times)

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Offline anotherCB

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Re: K8 Engine Damage - cam shaft sprocket in pieces
« Reply #125 on: September 04, 2020, 09:20:51 AM »
No risk to run out of season. 12 months over here in Central Texas 8) 8) 8)
1978 CB750K, 2016 R1200 GS/LC, 1973 R75/5

Offline bryanj

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Re: K8 Engine Damage - cam shaft sprocket in pieces
« Reply #126 on: September 04, 2020, 10:18:48 AM »
Season! Here in UK blink and you miss it!!!
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).

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Offline beemerbum

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Re: K8 Engine Damage - cam shaft sprocket in pieces
« Reply #127 on: September 04, 2020, 03:31:56 PM »
Does anyone really care anymore about this guy's problem?

Why do you reply if you don't care? I think I "owe" it to everyone who helped me with my problem to tell the story to the end.
You are absolutely right. Brain fart on my end. Please accept my apology

Offline anotherCB

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Re: K8 Engine Damage - cam shaft sprocket in pieces
« Reply #128 on: September 05, 2020, 02:57:11 PM »
@754 that's what I thought, it looked ok and I will check compression and leak down again after 100 mls or so.

@Beemerbum, no worries mate!
1978 CB750K, 2016 R1200 GS/LC, 1973 R75/5

Offline anotherCB

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Re: K8 Engine Damage - cam shaft sprocket in pieces
« Reply #129 on: September 06, 2020, 05:39:11 PM »
Good news, starts, runs, doesn't smoke or leak, no funny noises!
Video includes walk around, for start-up fwd to 1:30.

1978 CB750K, 2016 R1200 GS/LC, 1973 R75/5

Offline Jerry Rxman Griffin aka MuthaF'er

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Re: K8 Engine Damage - cam shaft sprocket in pieces
« Reply #130 on: September 06, 2020, 06:17:15 PM »
Congratulations! Not only does it sound good but it looks killer. It's not idling too low as long as you have good oil pressure.
As of today 3/13/2012 my original owner 75 CB750F has made it through 3 wives, er EX-wives. Free at last.  ;-)

Offline scottly

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Re: K8 Engine Damage - cam shaft sprocket in pieces
« Reply #131 on: September 06, 2020, 07:36:32 PM »
It sounds like it might not be hitting on all 4 cylinders when you open the throttle? Do a spit-sizzle test on the pipes...
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Offline anotherCB

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Re: K8 Engine Damage - cam shaft sprocket in pieces
« Reply #132 on: September 06, 2020, 08:01:42 PM »
Congratulations! Not only does it sound good but it looks killer. It's not idling too low as long as you have good oil pressure.

Thanks to help of a lot of folks on this forum it was a walk in the park  :). But i agree, I think it runs really well.

It sounds like it might not be hitting on all 4 cylinders when you open the throttle? Do a spit-sizzle test on the pipes...

I did that test and it runs an all 4 cylinders. Problem is, giving it throttle off idle, there is a flat spot, I assume caused by the stacks. They are good at idle and WOT. Next steps will be to re-route the oil hoses and get the airbox on.
1978 CB750K, 2016 R1200 GS/LC, 1973 R75/5

Offline scottly

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Re: K8 Engine Damage - cam shaft sprocket in pieces
« Reply #133 on: September 06, 2020, 08:03:35 PM »
Accelerator pump working?
Don't fix it if it ain't broke!
Helmets save brains. Always wear one and ride like everyone is trying to kill you....

Offline anotherCB

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Re: K8 Engine Damage - cam shaft sprocket in pieces
« Reply #134 on: September 07, 2020, 10:24:39 AM »
Accelerator pump working?

Very valid question! They worked when I took the carbs off 4 weeks ago, so I strongly assume they still work. But will definitely check again before the airbox goes on.
1978 CB750K, 2016 R1200 GS/LC, 1973 R75/5

Offline anotherCB

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Re: K8 Engine Damage - cam shaft sprocket in pieces
« Reply #135 on: September 14, 2020, 08:00:53 AM »
I have some good news to share. Engine rebuild was a full success. Thanks to everyone’s input, couldn’t have done it alone!
I installed the airbox but obviously since carbs were jetted for stacks it ran way to rich, so just to get some miles on, I switched back to the stacks for now before taking the carbs back off. Engine runs great, I just ran into one problem: Need to change the fuel filter every 3 miles or so, since it gets clogged up. I had hoped the tank was good to go with some cleaning I did but it appears not. Check out the pic, liner comes off in places and there is some rust and there was also hunk at the bottom which I had thought I cleaned out well enough.
So maybe I need to do a full tank cleaning job, acetone to get the liner out, muriatic acid for the rust. What do y’all think based on the pic?
1978 CB750K, 2016 R1200 GS/LC, 1973 R75/5

Offline 754

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Re: K8 Engine Damage - cam shaft sprocket in pieces
« Reply #136 on: September 14, 2020, 09:54:07 AM »
I would rattle out the  loose stuff, and hope more liner does not release. Then try it, clean bowl often see if its liveable or not.
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Offline anotherCB

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Re: K8 Engine Damage - cam shaft sprocket in pieces
« Reply #137 on: September 14, 2020, 12:02:09 PM »
I would rattle out the  loose stuff, and hope more liner does not release. Then try it, clean bowl often see if its liveable or not.

Kinda impossible to take bowls off with carb on, isn't it? Would't want to remove carbs every time.
1978 CB750K, 2016 R1200 GS/LC, 1973 R75/5

Offline robvangulik

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Re: K8 Engine Damage - cam shaft sprocket in pieces
« Reply #138 on: September 14, 2020, 03:17:33 PM »
Do as Delta always advertises 8) and use 4mm Allen screws instead of the standard JIS screws for the floatbowls, much easier to take the bowls out with the carbs still on the bike.

Offline anotherCB

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Re: K8 Engine Damage - cam shaft sprocket in pieces
« Reply #139 on: September 14, 2020, 03:29:11 PM »
Do as Delta always advertises 8) and use 4mm Allen screws instead of the standard JIS screws for the floatbowls, much easier to take the bowls out with the carbs still on the bike.

Good point!
1978 CB750K, 2016 R1200 GS/LC, 1973 R75/5

Offline robvangulik

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Re: K8 Engine Damage - cam shaft sprocket in pieces
« Reply #140 on: September 14, 2020, 05:42:10 PM »
They're small and tucked away, no-one will notice (if you should mind) ;)

Offline anotherCB

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Re: K8 Engine Damage - cam shaft sprocket in pieces
« Reply #141 on: September 27, 2020, 12:42:49 PM »
Last post on this thread. Bike is running great, drained the fuel through a coffee filter and got some chunks of dirt out. Cleaned the carbs again and installed on oversized in line fuel filter. Went on a 50 mls ride yesterday, no leaks, no issues, all great!!! Just some electric gremlins left so I need to navigate over to the Motogadget forum. Thanks again for everyone’s help, could have done it without y’all!
1978 CB750K, 2016 R1200 GS/LC, 1973 R75/5

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Re: K8 Engine Damage - cam shaft sprocket in pieces
« Reply #142 on: September 27, 2020, 11:20:45 PM »
I would use Metalready or other rust converter that doesn't attack plain steel on the tank. Failed liners are the pits!
David- back in the desert SW!

Offline PeWe

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Re: K8 Engine Damage - cam shaft sprocket in pieces
« Reply #143 on: September 28, 2020, 11:32:16 AM »
Check plugs a good thing too now and then. Not grey-white or pitch black or oily.
CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Offline anotherCB

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Re: K8 Engine Damage - cam shaft sprocket in pieces
« Reply #144 on: September 28, 2020, 12:25:21 PM »
I would use Metalready or other rust converter that doesn't attack plain steel on the tank. Failed liners are the pits!

May try that if the tank gives me more issues, thanks!


Check plugs a good thing too now and then. Not grey-white or pitch black or oily.

I know it's running a bit rich at idle and at least up to 1/4 throttle. I have 3 washers under the needle, should probably go down to 2. Also need to play a bit with the idle screw. I'll do all that soon and also still need to sync the carb properly. Little things will keep me busy for a while but I can ride at least! I prefer too rich over too lean to start out.
1978 CB750K, 2016 R1200 GS/LC, 1973 R75/5

Offline Dunk

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Re: K8 Engine Damage - cam shaft sprocket in pieces
« Reply #145 on: September 28, 2020, 05:30:54 PM »
Wow, I must have got real lucky with mine that had loose bolts and was making noise for years and a few thousand miles before it got worse and I pulled it apart. Picture is exactly how I found it...

Offline andy750

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Re: K8 Engine Damage - cam shaft sprocket in pieces
« Reply #146 on: September 28, 2020, 06:09:36 PM »
Congratulations and what a great thread! Thanks for all the updates and for keeping at it - I was waiting for the ride report and got it at the end so thank you! Enjoy your bike!
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1. CB750K4: Long distance bike, 17 countries and counting...2001 - Trans-USA-Mexico, 2003 - European Tour, 2004 - SOHC Easy Rider Trip , 2008 - Adirondack Tour 2-up , 2013 - Tail of the Dragon Tour , 2017: 836 kit install and bottom end rebuild. And rebirth: http://forums.sohc4.net/index.php/topic,173213.msg2029836.html#msg2029836
2. CB750/810cc K2  - road racer with JMR worked head 71 hp
3. Yamaha Tenere T700 2022

Where did you go on your bike today? - http://forums.sohc4.net/index.php?topic=45183.2350

Offline anotherCB

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Re: K8 Engine Damage - cam shaft sprocket in pieces
« Reply #147 on: September 29, 2020, 06:28:56 AM »
Wow, I must have got real lucky with mine that had loose bolts and was making noise for years and a few thousand miles before it got worse and I pulled it apart. Picture is exactly how I found it...

Wow, lucky you!
I need to look at the positive side, now I know my engine in and out, stayed sane through Covid, have bead blasted top and bottom ends, and have a few hundred bucks less that I NOT need to worry about to spend  :)

Congratulations and what a great thread! Thanks for all the updates and for keeping at it - I was waiting for the ride report and got it at the end so thank you! Enjoy your bike!

My pleasure, thanks for following along!
1978 CB750K, 2016 R1200 GS/LC, 1973 R75/5

Offline PeWe

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Re: K8 Engine Damage - cam shaft sprocket in pieces
« Reply #148 on: September 29, 2020, 07:03:34 AM »
That is the right attitude!!

I have encountered problems with bike before and in the end I saw the good things, better prepared for next time.

I blew my new 836 RC forged pistons, some valves, guides, all 4 rods at the first summer using it 1984.
I was happy that I lived, not failed 2500km earlier down in Jugoslavia.
Bike back on the roads following season.

Minor mistake 2 years ago when I ordered 20 clamps for carbs. 32-50, 12mm wide.
I should have 9mm wide.

I had use of those wide clamps yesterday when my K6 got new carb boots.
2 of the old (Honda) had cracked wide open. Lucky that pistons did not melt.
Newer Honda carb boots are softer, possible to tighten clamp too hard I guess. It crack just were spigot on head start under clamp.

I tested my wider (12mm) that fits very well!
No need to clamp that hard since clamp cover the entire area where rubber sit over spigot. I believe in this, hopefully live longer than the previous one, 20.000 km, 4 years.

Todays mistake can save the future!! :D
CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Offline anotherCB

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Re: K8 Engine Damage - cam shaft sprocket in pieces
« Reply #149 on: September 29, 2020, 01:16:02 PM »
Now I need to go check my clamps :-)
1978 CB750K, 2016 R1200 GS/LC, 1973 R75/5