Author Topic: CB750F3 Aftermarket valve hardware?  (Read 528 times)

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Offline Davidov

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CB750F3 Aftermarket valve hardware?
« on: May 16, 2014, 07:54:45 AM »
The previous owner of my 78 CB750F said he "thought" the head had a valve job done previously. I know I can't go off someone's word alone. He honestly said he had no way to prove it was done.

I'm preparing to remove the engine and do a freshen-up rebuild.
Is there a way to visually determine if the valve spring retainers or guides have been replaced? Do aftermarket components look different from factory parts?

-David

Offline flybox1

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Re: CB750F3 Aftermarket valve hardware?
« Reply #1 on: May 16, 2014, 08:11:33 AM »
post of pictures of what you find....
bronze valve guides are often used
'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

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Offline 70CB750

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Re: CB750F3 Aftermarket valve hardware?
« Reply #2 on: May 16, 2014, 08:14:50 AM »
This is helpful when looking at F3 valve train:

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Offline Davidov

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Re: CB750F3 Aftermarket valve hardware?
« Reply #3 on: May 16, 2014, 02:13:03 PM »
Awesome ID guide!

If my valve guide play is ok, and none of the retainers look damaged...should they still be replaced?

Even though mine is considered a F3 by serial number, did these still have the same valve problems?

-David

Offline flybox1

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Re: CB750F3 Aftermarket valve hardware?
« Reply #4 on: May 16, 2014, 02:18:43 PM »
I just rebuilt my F3 head over the winter.
the question i'd be asking is if the rebuild was with quality components.  If it looks like its had a valve job, and all valves seat well and dont leak(kerosene, mineral spirits, etc.) id, at a minimum, i'd replace the guide seals with OEM Honda guide seals, and reassemble.
'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

Past Bikes
1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
77/78 cool 2 member #3
"Knowledge without mileage equals bullsh!t" - Henry Rollins

"This is my CB. There are many like it, but this one is mine…"

Offline Davidov

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Re: CB750F3 Aftermarket valve hardware?
« Reply #5 on: May 22, 2014, 05:27:35 AM »
I just rebuilt my F3 head over the winter.
the question i'd be asking is if the rebuild was with quality components.  If it looks like its had a valve job, and all valves seat well and dont leak(kerosene, mineral spirits, etc.) id, at a minimum, i'd replace the guide seals with OEM Honda guide seals, and reassemble.

Of course the valve guide seals will get replaced.
My concern is having the notorious "F head" valve failure after doing a rebuild. Also trying to minimize unnecessary costs by replacing only worn components.
-David

Offline flybox1

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Re: CB750F3 Aftermarket valve hardware?
« Reply #6 on: May 22, 2014, 09:02:40 AM »
If your engine is out, it looks like you're on your way to spending some cash.
If its still in the frame, tune it up and ride it until it NEEDS to be overhauled.
save some cash in the meantime so you, or someone else can do it right. 
talk to MRieck, Hondaman about your specific concerns.
'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

Past Bikes
1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
77/78 cool 2 member #3
"Knowledge without mileage equals bullsh!t" - Henry Rollins

"This is my CB. There are many like it, but this one is mine…"