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Author Topic: Question on putting a '77 CB750F motor in a '77 CB750K frame  (Read 661 times)

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Offline Macmcgough

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Question on putting a '77 CB750F motor in a '77 CB750K frame
« on: October 18, 2017, 07:24:25 AM »
Hi! I'm a new member and have been working on/ riding these old 750 SOHC's since they were new in the showroom. (Yes, I'm old)
 But I've had an old 77 CB750K sitting in my garage for years now waiting for an engine.
 I  just picked a up good '77 CB750F engine, carbs, air-box, oil tank and exhaust yesterday
that I want to put in it. But for all the engine swaps I've done on these bikes over the
years, this is the first time I've tried this one.
 Does anyone know if this a direct bolt-in, or will frame/engine modifications be needed?
 Any help would be appreciated and a great time saver.
Thanks to any all for any help!     
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Offline MD

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Re: Question on putting a '77 CB750F motor in a '77 CB750K frame
« Reply #1 on: October 18, 2017, 06:11:14 PM »
Welcome from NE MN,

I am not as old as you, but my 550 sat for 20+years.  Others will help you with your 750 question.

-MD
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1975 CB550F Super Sport;  Lake Superior Circle 1000, 45-90 Saddle 1000, All in Yooper 1000 and SS 2000 in 48 hrs:  1985 GL1200A, MN in State SS1K

Online madmtnmotors

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Re: Question on putting a '77 CB750F motor in a '77 CB750K frame
« Reply #2 on: October 18, 2017, 06:31:27 PM »
Straight bolt in with the possible exception of the exhaust. You may need to source a "K" exhaust, but you will know for sure when you try to install the "F" exhaust. The F footpegs and brake lever are a little different than the K. Good luck with your new project, and if the F motor is tight (good compression) you should end up with a good runner.  8)
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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

Sent from my Tandy TRS-80!

Offline seanbarney41

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Re: Question on putting a '77 CB750F motor in a '77 CB750K frame
« Reply #3 on: October 18, 2017, 06:44:19 PM »
yup, and if your new to cb750's with the F2/3 lump, your gonna like the extra power...not a huge amount more but let us know what you think!
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If it works good, it looks good...

Offline Macmcgough

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Re: Question on putting a '77 CB750F motor in a '77 CB750K frame
« Reply #4 on: October 18, 2017, 09:13:51 PM »
 Thank you gentleman for your help, I thought it was but, with the wealth of proven knowledge on this site, I thought it couldn't hurt to ask. (BEFORE I crushed my fingers between the engine and the frame trying to make mismatched bolt holes line up!)
 But no, I'm not new these bikes, I'm 63 years young, and and loved bikes since my buddy on his bobbed and molded '69 CB750K outran me on my '67 Triumph Tiger 500 with duel carbs, and .60 overbore with Chevy valves. And his bike didn't cost half as much as mine!
 Good day to you gentleman, and keep the rubber side down!

Currant bikes:
'73 CB750K
'79 Honda CX500C
'84 V65 Magna
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Offline Jerry Rxman Griffin aka MuthaF'er

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Re: Question on putting a '77 CB750F motor in a '77 CB750K frame
« Reply #5 on: October 19, 2017, 10:55:20 AM »
Hey kid, welcome from one of the old guys. Direct swap. Are you done yet?

As Wilbur states the only thing you'll run into will be the exhaust and carb boots (head fitment) depending on which ones you have. May need to use your K system or get an after market if you want a 4:1 if the F system doesn't fit.
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As of today 3/13/2012 my original owner 75 CB750F has made it through 3 wives, er EX-wives. Free at last.  ;-)
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