Author Topic: My K8 re-conditioning  (Read 18853 times)

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Online denward17

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Re: My K8 re-conditioning
« Reply #25 on: December 01, 2022, 11:02:10 AM »
Where is it leaking oil from?

I assume the pucks and neutral safety switch.  Where else ?


Offline MauiK3

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Re: My K8 re-conditioning
« Reply #26 on: December 01, 2022, 11:13:37 AM »
Nice project, following
1973 CB 750 K3
10/72 build Z1 Kawasaki

Offline newday777

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Re: My K8 re-conditioning
« Reply #27 on: December 01, 2022, 11:30:24 AM »
Cool idea Den.
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

Online denward17

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Re: My K8 re-conditioning
« Reply #28 on: December 15, 2022, 12:34:30 PM »
Not much to report, been cleaning and sanding and finally all parts got here to repair oil leaks.

Thought I would finish cleaning and sanding before taking cam shaft out to repair pucks.  After repairs are done, will complete cleaning and get it ready for paint.

Can't seem to find enough time to get things done lately.


Offline BenelliSEI

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Re: My K8 re-conditioning
« Reply #29 on: December 16, 2022, 06:33:29 AM »
Nice cleanup. Using Duplicolor 1615 engine paint? They make a nice “filler primer” for use with their spray paints that covers any scratches or less than perfect castings. Works well.

Online denward17

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Re: My K8 re-conditioning
« Reply #30 on: December 16, 2022, 08:54:15 AM »
Nice cleanup. Using Duplicolor 1615 engine paint? They make a nice “filler primer” for use with their spray paints that covers any scratches or less than perfect castings. Works well.

Yes, DE 1615.  Haven't given much thought to the filler primer.

Offline BenelliSEI

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Re: My K8 re-conditioning
« Reply #31 on: December 17, 2022, 02:32:01 PM »
I tried the primer years ago on a sump and lower case that had some corrosion damage. Worked well and “smoothed” the imperfections nicely. The finish was so nice, I use it all the time now.

Online grcamna2

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Re: My K8 re-conditioning
« Reply #32 on: December 17, 2022, 03:37:26 PM »
I tried the primer years ago on a sump and lower case that had some corrosion damage. Worked well and “smoothed” the imperfections nicely. The finish was so nice, I use it all the time now.

The Duplicolor engine heat paint primer ?
I used that before with similar results;a good base for the DE1615.
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 BenelliSEI

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Re: My K8 re-conditioning
« Reply #33 on: December 17, 2022, 05:43:08 PM »
I thought what I used was “filler primer”, but not so sure. I’ll dig out a can, next shop visit.

Online denward17

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Re: My K8 re-conditioning
« Reply #34 on: December 20, 2022, 07:25:03 AM »
After leak down test showed some issues, looks like I will have to pull head and do some work.

Haven't decided how far to go yet, my brain tells me at least a valve job and new rings while it it open.

Offline BenelliSEI

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Re: My K8 re-conditioning
« Reply #35 on: December 20, 2022, 09:19:10 AM »
Been following along and also read some of your “leakdown” posts. I’m doing much the same work to my bike (see my “Early Sandcast found” project posts. I always start by getting my project bike running. That usually tells me what needs doing. My engine definitely had the pucks leaking, so I’m digging in, just like you. I also have some bent and cracked cooling fins on the barrel section, so needed to pull the top end apart, to get that part vapour blasted and repaired. While it’s on the bench, I’m going to give it a light hone, new rings, gaskets, “0” rings and seals. The valves are out of the head and just need a light clean, lapping and re assembly. None of this was really necessary, but I have lots of time and this bike is worth some extra effort.......

Looking at your engine photos, the base gasket and head gasket look tight. If I were you, I’d pull the cam, rocker gear and cam pedestals. You need new new pucks and “0” rings under there for sure. When the top of the head is bare, retorque the head. Put number 1 and 4 cylinders at TDC. Now check the leak down on those two cylinders. If you hear leaking at the intake or exhaust valve, drop the piston down the bore 1/2 way and strike the valve head sharply a few time, with a soft hammer. Make it pop open and shut, with the air pressure on. This will clear any crud from under the valve sea and give you a much more accurate reading. I assume your engine has not run for a while? Your rings are bone dry, so you might be wise to spray some WD40 in there and rotate a few times first.....

If you get reasonable readings across the 4 cylinders this way, just leave it alone..... 
« Last Edit: December 20, 2022, 09:21:22 AM by BenelliSEI »

Online denward17

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Re: My K8 re-conditioning
« Reply #36 on: December 20, 2022, 10:02:29 AM »
Thanks Benelli, will give that a try.

Offline BenelliSEI

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Re: My K8 re-conditioning
« Reply #37 on: December 20, 2022, 10:24:42 AM »
Good luck.... report what you find.

Online denward17

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Re: My K8 re-conditioning
« Reply #38 on: December 20, 2022, 01:11:07 PM »
Another test completed:

Cam out, head retorqued (except the bolts under the pucks)  Is there a torque value for them?


Number 3 was the best at around 20%, Number 1 and 2 were about 35% and number 4 was just over 50%

Numbers did improve just a little after re-torque.


What to do now, leave it, or take head off for valve job?

Offline BenelliSEI

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Re: My K8 re-conditioning
« Reply #39 on: December 20, 2022, 06:17:40 PM »
Is it snowing where you live? Do it now.

Online grcamna2

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Re: My K8 re-conditioning
« Reply #40 on: December 20, 2022, 06:22:26 PM »
Another test completed:

Cam out, head retorqued (except the bolts under the pucks)  Is there a torque value for them?


Number 3 was the best at around 20%, Number 1 and 2 were about 35% and number 4 was just over 50%

Numbers did improve just a little after re-torque.


What to do now, leave it, or take head off for valve job?

I would remove it and do the valve job.

The valve seats and valve guides condition is unknown to you right now;the valves all sealing properly and guides being 'within spec' equally on all 4 cylinders will make that bike perform the way it should  ;) rather than one cylinder pushing-out more power and working harder to 'carry' the other ones that are lagging behind.  ::)
« Last Edit: December 20, 2022, 09:20:48 PM by grcamna2 »
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.

Online denward17

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Re: My K8 re-conditioning
« Reply #41 on: December 20, 2022, 07:59:12 PM »
Is it snowing where you live? Do it now.

Not snowing in NC where I live, but cold.

Offline 70CB750

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Re: My K8 re-conditioning
« Reply #42 on: December 21, 2022, 02:35:46 AM »
Hello from VA  ;D

Following. 
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Online denward17

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Re: My K8 re-conditioning
« Reply #43 on: December 22, 2022, 08:06:26 AM »
Working on getting the head/cylinders off today.

I removed the cam tower studs and could not believe how loose they were.  I looked for my stud remover, couldn't find it so tried the double nut method, came out almost too easy.  No wonder this thing leaked oil so bad.  Between the pucks and these studs, I understand now how these engines can leak so easily.

Online denward17

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Re: My K8 re-conditioning
« Reply #44 on: December 22, 2022, 08:13:42 AM »
Hello from VA  ;D

Following.

Hello 70CB750, what part of Va ?

I'm in central NC, near Raleigh.

Offline BenelliSEI

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Re: My K8 re-conditioning
« Reply #45 on: December 22, 2022, 10:17:55 AM »
Working on getting the head/cylinders off today.

I removed the cam tower studs and could not believe how loose they were.  I looked for my stud remover, couldn't find it so tried the double nut method, came out almost too easy.  No wonder this thing leaked oil so bad.  Between the pucks and these studs, I understand now how these engines can leak so easily.

Good call. Do it now and you’ll have spent your time well!

Online denward17

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Re: My K8 re-conditioning
« Reply #46 on: December 22, 2022, 10:35:57 AM »
Head and cylinders are off, now time to do some cleaning and pull the valves out.

How do these pictures look for wear?  I suppose I need to get new rings since I took the cylinders off.

What's a good source for rings/gaskets?


Thanks for any info.


Online denward17

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Re: My K8 re-conditioning
« Reply #47 on: December 22, 2022, 10:37:52 AM »
more pics:

Does the rubber rollers look ok to re-use?

« Last Edit: December 22, 2022, 10:44:17 AM by denward17 »

Online denward17

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Re: My K8 re-conditioning
« Reply #48 on: December 22, 2022, 10:39:21 AM »
more

Online denward17

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Re: My K8 re-conditioning
« Reply #49 on: December 22, 2022, 10:42:56 AM »
more
« Last Edit: December 22, 2022, 10:44:59 AM by denward17 »