Author Topic: Cobra motor disassembly and rebuild  (Read 107784 times)

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Offline kmb69

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Re: Cobra motor disassembly and rebuild
« Reply #650 on: November 20, 2016, 04:25:04 PM »
Lol, next season fellas, next season. Still shooting for consistent ETs on my current bike- it'll never see a 9. But i do want to win a race with it and finish in the top 5 in the field. I fell short of that goal this year but I'm not giving up. I'll freshen it up over the winter with a new crank.

 The nines are reserved for the project bike. Lots of work ahead so its going to be a long winter in the shop working with my junk parts. Stay tuned, I got high hopes. Hahaha. Remember now, the Honda is the slowest bike I own. Most are in the 8's and one is capable of running mid sevens on spray. Nothing to prove here.

Frankie, we know you BAAADDD!!  ;)  8)

But some of us nostalgic, Honda fools fanatics want to present a respectable performance without having to go Kaw, Suz, Yam, NOS, or Puff.  ???

Hell, I would just buy a Busa if it was all about ET or MPH. Lots cheaper than making a Honda GO!  ::)

Fortune: Confucius say, "Beware of Billy cranks!"  ;D  ;D  ;D

Offline Bill/BentON Racing

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Re: Cobra motor disassembly and rebuild
« Reply #651 on: November 20, 2016, 05:56:57 PM »
Yep, I realized how lucky I was......It was running so good, love the color of the top of pistons
« Last Edit: November 20, 2016, 06:08:53 PM by Bill/BentON Racing »
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Over 35 years of experience working on vintage motorcycles, with a speciality in Honda SOHC/4 with a focus on the CB750 and other models as well from 1966 - 1985.
______________________________________
1993 HRC RS125 | 1984 NS400R | 1974 Honda CB750/836cc (Calendar Girl) | 1972 CB 500/550 Yoshi Kitted 590cc | 1965 Honda CB450 Black Bomber | 1972 Suzuki T350 | 1973 88cc | Z50/Falcons Pit Bike | 1967 CA100| 1974 CB350 (400F motor)...and more.
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Offline kmb69

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Re: Cobra motor disassembly and rebuild
« Reply #652 on: November 20, 2016, 06:12:15 PM »
I'm curious to see the #3 combustion chamber...

Ouch! :o  :o  :o

It might buff out!  ;D


Offline kmb69

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Re: Cobra motor disassembly and rebuild
« Reply #653 on: November 20, 2016, 06:14:27 PM »
Billy, some of those teeth on that tensioner don't look so good. Is that true or an optical "delusion"?

Offline MRieck

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Re: Cobra motor disassembly and rebuild
« Reply #654 on: November 20, 2016, 06:33:35 PM »
Billy, some of those teeth on that tensioner don't look so good. Is that true or an optical "delusion"?
Yes.....they are F'd up. Chamber color is really nice. I cannot find any fault there.
Owner of the "Million Dollar CB"

Offline Bill/BentON Racing

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Re: Cobra motor disassembly and rebuild
« Reply #655 on: November 20, 2016, 07:16:04 PM »
Yep, not impressed!
« Last Edit: November 20, 2016, 07:28:45 PM by Bill/BentON Racing »
BentON Racing Website
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Over 35 years of experience working on vintage motorcycles, with a speciality in Honda SOHC/4 with a focus on the CB750 and other models as well from 1966 - 1985.
______________________________________
1993 HRC RS125 | 1984 NS400R | 1974 Honda CB750/836cc (Calendar Girl) | 1972 CB 500/550 Yoshi Kitted 590cc | 1965 Honda CB450 Black Bomber | 1972 Suzuki T350 | 1973 88cc | Z50/Falcons Pit Bike | 1967 CA100| 1974 CB350 (400F motor)...and more.
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Offline kmb69

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Re: Cobra motor disassembly and rebuild
« Reply #656 on: November 20, 2016, 07:32:58 PM »
Yep, not impressed!

It's not as hard as the chain but harder than rubber.
Lots of shrapnel went thru there. Not sure but maybe it did what it was suppose to.
What ya think Mike?

Interested to see what the other wrist pins look like.



Offline 754

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Re: Cobra motor disassembly and rebuild
« Reply #657 on: November 20, 2016, 07:47:04 PM »
#3. Chamber looks better than I expected, valves will need lapping.

I think I still have probably the most cracked set of cases... I think around two feet of cracks.
 From counter shaft to oil pressure hole top an bottom, plus 3 more cracks at main bearing on #1..
 Worst part, I was on the bike when it happened...
Maker of the WELDLESS 750 Frame Kit
dodogas99@gmail.com
Kelowna B.C.       Canada

My next bike will be a ..ANFOB.....

It's All part of the ADVENTURE...

73 836cc.. Green, had it for 3 decades!!
Lost quite a few CB 750's along the way

Offline Bill/BentON Racing

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Re: Cobra motor disassembly and rebuild
« Reply #658 on: November 20, 2016, 07:51:09 PM »
Pics please!
BentON Racing Website
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Over 35 years of experience working on vintage motorcycles, with a speciality in Honda SOHC/4 with a focus on the CB750 and other models as well from 1966 - 1985.
______________________________________
1993 HRC RS125 | 1984 NS400R | 1974 Honda CB750/836cc (Calendar Girl) | 1972 CB 500/550 Yoshi Kitted 590cc | 1965 Honda CB450 Black Bomber | 1972 Suzuki T350 | 1973 88cc | Z50/Falcons Pit Bike | 1967 CA100| 1974 CB350 (400F motor)...and more.
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Offline Bill/BentON Racing

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Re: Cobra motor disassembly and rebuild
« Reply #659 on: November 20, 2016, 07:52:11 PM »
Big roller looked good.
BentON Racing Website
OEM Parts | Service | Custom Builds
BentON Racing Facebook
Over 35 years of experience working on vintage motorcycles, with a speciality in Honda SOHC/4 with a focus on the CB750 and other models as well from 1966 - 1985.
______________________________________
1993 HRC RS125 | 1984 NS400R | 1974 Honda CB750/836cc (Calendar Girl) | 1972 CB 500/550 Yoshi Kitted 590cc | 1965 Honda CB450 Black Bomber | 1972 Suzuki T350 | 1973 88cc | Z50/Falcons Pit Bike | 1967 CA100| 1974 CB350 (400F motor)...and more.
______________________________________
See our latest build 'Captain Marvel' CLICK HERE

Offline knowsnothing

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Re: Cobra motor disassembly and rebuild
« Reply #660 on: November 20, 2016, 08:17:19 PM »
So piston, pin or rod failure?  Or D - all of the above?

1978 CB750k Green - 811 engine
1978 CB750k Blue - for sale
1974 CB375F Faded Black - had to have that 6th gear
1976 CB400F Red - in many pieces
1973 CB350F TBD - in many pieces

Offline dragracer

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Re: Cobra motor disassembly and rebuild
« Reply #661 on: November 20, 2016, 09:12:24 PM »
Lol, next season fellas, next season. Still shooting for consistent ETs on my current bike- it'll never see a 9. But i do want to win a race with it and finish in the top 5 in the field. I fell short of that goal this year but I'm not giving up. I'll freshen it up over the winter with a new crank.

 The nines are reserved for the project bike. Lots of work ahead so its going to be a long winter in the shop working with my junk parts. Stay tuned, I got high hopes. Hahaha. Remember now, the Honda is the slowest bike I own. Most are in the 8's and one is capable of running mid sevens on spray. Nothing to prove here.

Frankie, we know you BAAADDD!!  ;)  8)

But some of us nostalgic, Honda fools fanatics want to present a respectable performance without having to go Kaw, Suz, Yam, NOS, or Puff.  ???

Hell, I would just buy a Busa if it was all about ET or MPH. Lots cheaper than making a Honda GO!  ::)

Fortune: Confucius say, "Beware of Billy cranks!"  ;D  ;D  ;D


Well, I'm not that BAD. But I think i'm starting to get the picture. Chasing a 70's dream in 2016.

 

Offline dragracer

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Re: Cobra motor disassembly and rebuild
« Reply #662 on: November 20, 2016, 09:16:22 PM »
Hey Billy, you got any used pistons and wrist pins I can buy?? I'm gonna build an entire consumable motor- just like you.  ;D

Offline calj737

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Re: Cobra motor disassembly and rebuild
« Reply #663 on: November 21, 2016, 03:43:56 AM »
Update: For Sale
Slightly used race engine. Ran low 10's when parked. Will ship to you. Make offer
- Bill Benton
'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 Bill/BentON Racing

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Re: Cobra motor disassembly and rebuild
« Reply #664 on: November 21, 2016, 04:36:24 AM »
LMAO,  I got 3 pins for you!  Lol. Pricey though! ;D, Bill
BentON Racing Website
OEM Parts | Service | Custom Builds
BentON Racing Facebook
Over 35 years of experience working on vintage motorcycles, with a speciality in Honda SOHC/4 with a focus on the CB750 and other models as well from 1966 - 1985.
______________________________________
1993 HRC RS125 | 1984 NS400R | 1974 Honda CB750/836cc (Calendar Girl) | 1972 CB 500/550 Yoshi Kitted 590cc | 1965 Honda CB450 Black Bomber | 1972 Suzuki T350 | 1973 88cc | Z50/Falcons Pit Bike | 1967 CA100| 1974 CB350 (400F motor)...and more.
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See our latest build 'Captain Marvel' CLICK HERE

Offline kmb69

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Re: Cobra motor disassembly and rebuild
« Reply #665 on: November 21, 2016, 06:10:25 AM »
..... But I think i'm starting to get the picture. Chasing a 70's dream in 2016.

Bingo! Sick ain't it!  ;)

Offline POPS 911

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Re: Cobra motor disassembly and rebuild
« Reply #666 on: November 21, 2016, 06:56:34 AM »
BILL:  Make a plaque to go on the wall of your trailer with that rod the center piece so every time you walk out of your trailer to throw your leg over the bike you can remember a DAY that things could have went really bad for BILL CHASING A DREAM, Daddy FRANK might not be there to PULL THAT KILL !!! Maybe the day to buy a turn key motor from APE would be a good thing = motor in a crate that runs 9's would be good for APE at a MAN CUP.

Offline kmb69

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Re: Cobra motor disassembly and rebuild
« Reply #667 on: November 21, 2016, 07:23:44 AM »
.....
Maybe the day to buy a turn key motor from APE would be a good thing = motor in a crate that runs 9's would be good for APE at a MAN CUP.

Dang Pops, Nothing like running a knife thru his heart!  :o

Offline madmtnmotors

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Re: Cobra motor disassembly and rebuild
« Reply #668 on: November 21, 2016, 08:20:16 AM »
.....
Maybe the day to buy a turn key motor from APE would be a good thing = motor in a crate that runs 9's would be good for APE at a MAN CUP.

Dang Pops, Nothing like running a knife thru his heart!  :o


and his wallet!
TAMTF...


Wilbur



Projects:
"Evolution": http://forums.sohc4.net/index.php?topic=100352.0
"P.O. Debacle": http://forums.sohc4.net/index.php/topic,126692.msg1441661.html#msg1441661
F2/F3 O-rings: http://forums.sohc4.net/index.php?topic=113672.msg1300721#msg1300721
Cam Tower Studs: https://www.mcmaster.com/#93210a017/=t19sgp
Clean up that nasty harness: http://forums.sohc4.net/index.php?topic=137351.msg1549191#msg1549191
http://forums.sohc4.net/index.php/topic,148188.msg1688494.html#msg1688494
http://forums.sohc4.net/index.php/topic,139544.msg1579364.html#msg1579364
                                          
Charging system diagnosis: http://forums.sohc4.net/index.php?topic=1012.msg8345#msg8345
Get the manuals: http://manuals.sohc4.net/cb750k/
The Dragon: http://forums.sohc4.net/index.php?topic=45183.msg1571675#msg1571675
Headlight Switch: http://forums.sohc4.net/index.php?topic=113986.msg1283236#msg1283236
Branden's leak free top end thread: http://forums.sohc4.net/index.php?topic=107040.0
Engine Lifting Made Easy: http://forums.sohc4.net/index.php/topic,58210.msg1684742.html#msg1684742
                                      http://forums.sohc4.net/index.php/topic,100352.msg1675840.html#msg1675840
Static and Dynamic Timing: http://www.hondachopper.com/garage/carb_info/timing/timing1.html
Airbox Gasket Replacement: http://forums.sohc4.net/index.php/topic,114485.msg1290000.html#msg1290000
"Café" : http://forums.sohc4.net/index.php/topic,84697.msg953814.html#msg953814
PD Carb Choke Linkage: http://forums.sohc4.net/index.php/topic,100352.msg1669248.html#msg1669248
                                    http://forums.sohc4.net/index.php/topic,110931.msg1248354.html#msg1248354
                                    http://forums.sohc4.net/index.php/topic,48858.msg515204.html#msg515204
Follow up on your damn posts: http://forums.sohc4.net/index.php/topic,144305.msg1791605.html#msg1791605
Taiwanese Cam Chain Tensioners:  http://forums.sohc4.net/index.php/topic,155043.msg1774841.html#msg1774841
Gumtwo Seat Cover: http://forums.sohc4.net/index.php/topic,164440.msg1897366.html#msg1897366
Primary Drive: http://forums.sohc4.net/index.php/topic,166063.msg1919278.html#msg1919278
Tank Latch: http://forums.sohc4.net/index.php/topic,165975.msg1919495.html#msg1919495
Shorten your forks: http://vintage-and-classic-honda-s.456789.n3.nabble.com/How-to-shorten-forks-td4042465.html DO NOT CUT THE SPRINGS!
Clutch How To: http://vintage-and-classic-honda-s.456789.n3.nabble.com/How-to-change-and-adjust-a-clutch-SOHC-td4040391.html
Late model K7/K8/F2/F3 front sprocket cover removal: http://forums.sohc4.net/index.php/topic,178428.msg2072279.html#msg2072279
630 to 530 conversion: http://forums.sohc4.net/index.php/topic,180710.msg2094423.html#msg2094423

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Offline Bill/BentON Racing

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Re: Cobra motor disassembly and rebuild
« Reply #669 on: November 21, 2016, 08:28:52 AM »
SMH, ......I'll keep building my engines....thank you, but it's my ass,  you only as good as the parts and your work. My work was fine and I'll put my build against anyone's....ain't that what we're doing. Yes I realized a dream on Saturday,  10's and a record,  but if you're lucky enough to live, you better LEARN,  I did! So I'm going forward. Don't forget even the best  forget stuff...like oil? Other people are fortunate also, I thank God I was OK and for the people who care, I know you do and Frank big time, so let's go forward,  you or anyone welcome to point out anything with that engine....it was built right, Bill
BentON Racing Website
OEM Parts | Service | Custom Builds
BentON Racing Facebook
Over 35 years of experience working on vintage motorcycles, with a speciality in Honda SOHC/4 with a focus on the CB750 and other models as well from 1966 - 1985.
______________________________________
1993 HRC RS125 | 1984 NS400R | 1974 Honda CB750/836cc (Calendar Girl) | 1972 CB 500/550 Yoshi Kitted 590cc | 1965 Honda CB450 Black Bomber | 1972 Suzuki T350 | 1973 88cc | Z50/Falcons Pit Bike | 1967 CA100| 1974 CB350 (400F motor)...and more.
______________________________________
See our latest build 'Captain Marvel' CLICK HERE

Offline TurboD

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Re: Cobra motor disassembly and rebuild
« Reply #670 on: November 21, 2016, 08:48:58 AM »
Keep digging Bill, everyone has troubles from time to time. Working on these old bikes are all the fun of it, and no one likes a "Store Bought" racer... hehe

Offline dragracer

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Re: Cobra motor disassembly and rebuild
« Reply #671 on: November 21, 2016, 10:44:18 AM »
We all give you credit for your achievements Bill. You made your dreams come true and set a record in the process. Weak parts were unfortunately your downfall in the end.

And yeah, I resemble that no oil jab!!

Offline kmb69

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Re: Cobra motor disassembly and rebuild
« Reply #672 on: November 21, 2016, 10:53:37 AM »
Track management will love you.  :-*

Lot easier and quicker to clean the track up when you blow one without oil in it!  ::)

Offline kmb69

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Re: Cobra motor disassembly and rebuild
« Reply #673 on: November 21, 2016, 10:57:16 AM »
.....
I think I still have probably the most cracked set of cases... I think around two feet of cracks.
From counter shaft to oil pressure hole top an bottom, plus 3 more cracks at main bearing on #1..
Worst part, I was on the bike when it happened...

Come on Frank, you know pics or it didn't happen.  ;)

Offline dragracer

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Re: Cobra motor disassembly and rebuild
« Reply #674 on: November 21, 2016, 12:01:29 PM »
Track management will love you.  :-*

Lot easier and quicker to clean the track up when you blow one without oil in it!  ::)


The key point here is to know when to quit. At the first sign of trouble we shut it down. Even my wife knows that is an important step.