Author Topic: '77 750K engine rebuild  (Read 1325 times)

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Offline wiskey

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'77 750K engine rebuild
« on: December 14, 2012, 07:21:53 AM »
I will try and make this as brief and straight to the point as possible.

last winter i brought a '77 back to life after sitting for 20+ years, I had a blast ripping her all over town however in late September I developed a lout "tick" noise. The bike ran for 5 min after the sound developed, I parked it and haven't touched it since. I will be tearing it down this winter and fixing/replacing what broke. I think it could be valve train related, however a friend of mine thinks I spun a bearing.

I want to build a fun yet street-able (reliable) motor. I'd like some insight to what other parts I should replace while i have the motor off.

Here is what I have so far:
-836 kit from ebay (pistons, rings, wrist pins, gaskets) (not installed)
-electronic ignition (pamco) 3ohm dyna coils & wires, iridium plugs
-factory air box with drop in k&n

I will be getting heavy duty studs and a new cam chain tensioner and cam chain. and of course replace whatever broke. I have been toying with the idea of head work and a mild cam but I know this starts to add cost quite fast

What else should I add to increase power and/or reliability. I would rather do things up front the right way and avoid doing things twice!

Thanks for the help!


Offline madmtnmotors

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Re: '77 750K engine rebuild
« Reply #1 on: December 14, 2012, 08:31:28 AM »
Open the inspection caps in the valve cover and check the valve adjusters first! I've had the locknut loosen up and the subsequent excessive lash and flailing rocker will make a heck of a racket!
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 iron_worker

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Re: '77 750K engine rebuild
« Reply #2 on: December 14, 2012, 09:35:53 AM »
I believe over size intake valves and a decent port job is supposed to be one of the first things to address on these motors. It is a bit of a bottleneck on the stock design. A cam with that work would really wake it up. Running the stock cam on a big bore might choke your power down a bit. The big bore will need the duration and lift to really allow it to breathe.

All depends on your budget though. I went through this same process and was pretty convinced I was going to do a big bore, lightened crank & alt, oversize intakes with superflow valves on both, ported and polished, a hotter came, stiffer springs, titanium retainers, digital ignition, etc etc etc. Then the price really started to escalate quickly and I realized my bike had too much sentimental value to hack it up like that. I decided that a stock type rebuild was more appropriate for my dad's old bike. I want it to be a reliable cruiser just like he used to ride.

It all comes down to what you want and how much you can reasonably budget.

IW

Offline knowsnothing

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Re: '77 750K engine rebuild
« Reply #3 on: December 14, 2012, 10:34:43 AM »
Open the inspection caps in the valve cover and check the valve adjusters first! I've had the locknut loosen up and the subsequent excessive lash and flailing rocker will make a heck of a racket!

+1 One loosed up on my 78, made an aweful noise.  Just had to reset it and everything was fine after.
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 wiskey

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Re: '77 750K engine rebuild
« Reply #4 on: December 14, 2012, 12:08:58 PM »
Open the inspection caps in the valve cover and check the valve adjusters first! I've had the locknut loosen up and the subsequent excessive lash and flailing rocker will make a heck of a racket!

Thanks hopefully I will get some time and check.