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Author Topic: 1978 F2 Inlet & Exhaust Valves in a1978 K8 ?  (Read 2543 times)

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Offline BMHS

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1978 F2 Inlet & Exhaust Valves in a1978 K8 ?
« on: July 15, 2010, 08:39:29 PM »
Guys,
Does anyone know of any logical reason why 1978 Honda F2 inlet and exhaust valves can't be put in a 1978 K8 cylinder head, using a Serdi machine to do the valve rework. I know the head diameters are larger, are the stem lengths the same? Anyone know the exact head diameters? I have two K8 heads I can measure.
Thanks
Brian
PS, It maybe easier to use Kibblewhite valves?
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Offline Old Scrambler

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Re: 1978 F2 Inlet & Exhaust Valves in a1978 K8 ?
« Reply #1 on: July 16, 2010, 10:10:32 AM »
I am also interested in this type of motor build. I plan to use the valves and cam from an F2 (or maybe a 41A Web cam) with K7 - K8 pistons for a mild upgrade in a cafe build. My local builder says he can do it but plans to use clay to check clearances before he turns the motor over.
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Offline MRieck

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Re: 1978 F2 Inlet & Exhaust Valves in a1978 K8 ?
« Reply #2 on: July 16, 2010, 12:17:39 PM »
Quote from: BMHS on July 15, 2010, 08:39:29 PM
Guys,
Does anyone know of any logical reason why 1978 Honda F2 inlet and exhaust valves can't be put in a 1978 K8 cylinder head, using a Serdi machine to do the valve rework. I know the head diameters are larger, are the stem lengths the same? Anyone know the exact head diameters? I have two K8 heads I can measure.
Thanks
Brian
PS, It maybe easier to use Kibblewhite valves?
Off hand I don't think you can get that F2 exhaust valve to fit on the K8 seat...it's to large. You really don't need that large an exhaust valve. You can go with a OS 33.5 intake valve and us the standard 28mm exhaust. I would go with the early style keeper retainer set up no matter what.....it's more reliable.
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Offline Big Jay

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Re: 1978 F2 Inlet & Exhaust Valves in a1978 K8 ?
« Reply #3 on: July 16, 2010, 09:44:56 PM »
Here are the sizes. http://cbrzone.com/sohc.html

The F2 valves are too big to fit on the K seats.
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Offline MRieck

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Re: 1978 F2 Inlet & Exhaust Valves in a1978 K8 ?
« Reply #4 on: July 17, 2010, 05:09:58 PM »
Quote from: Big Jay on July 16, 2010, 09:44:56 PM
Here are the sizes. http://cbrzone.com/sohc.html

The F2 valves are too big to fit on the K seats.
You can fit an F2 intake on the stock seat.....it's the same size as the 5mm conversion....34mm. I DO NOT recommend it.
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Offline Terry in Australia

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Re: 1978 F2 Inlet & Exhaust Valves in a1978 K8 ?
« Reply #5 on: July 18, 2010, 01:57:46 AM »
Why not just get APE to do a rebuilt F2 head for you? New stainless steel valves, new valve guides, Serdi valve job, etc etc. Looks like a bargain to me for 699 bucks, I might get one done for my 1060cc engine! Cheers, Terry. ;D
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Re: 1978 F2 Inlet & Exhaust Valves in a1978 K8 ?
« Reply #6 on: July 18, 2010, 09:54:51 AM »
Terry has a great idea but he failed to mention the other obstacles you'd have to overcome. It'd be an even better idea if APE threw in porting but we know it ain't gonna happen at that price  ;)
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Offline BMHS

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Re: 1978 F2 Inlet & Exhaust Valves in a1978 K8 ?
« Reply #7 on: July 18, 2010, 02:28:43 PM »
I just purchased a complete F2 top end, cylinder up. So it will give me a good idea what's involves with the changes between the two heads. I wouldn't go to anyone else for the head work, I owned the company, FlowRite Systems, a national cylinder head shop in the 1970 / 1980's. I can get excellent Serdi style head work locally here in WI. Thank you all for the input.
Brian
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Offline Terry in Australia

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Re: 1978 F2 Inlet & Exhaust Valves in a1978 K8 ?
« Reply #8 on: July 19, 2010, 05:29:04 AM »
If you've got an F2 top end mate, there are no other "obstacles", as Jerry has erroneously suggested. (he's a great pharmacist, but he's a terrible drunk, and doesn't know sh1t about building engines..... ;D)

And If I'm reading APE's advert right, they do include "some" port work work, i.e., matching the valve seats to the ports, so for 699 bucks, which includes new stainless valves, seats re-cut, head skimming and new valve guides, why would you bother doing it yourself? Cheers, Terry. ;D  

http://cbrzone.com/sohc.htm

« Last Edit: July 19, 2010, 05:34:03 AM by Terry in Australia »
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So I said, "Hey mate, you haven't got any bike boots you don't need, do you?"

"Crazy is a very misunderstood term, it's a fine line that some of us can lean over and still keep our balance" (thanks RB550Four)

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Re: 1978 F2 Inlet & Exhaust Valves in a1978 K8 ?
« Reply #9 on: July 19, 2010, 01:55:04 PM »
Now now Terry, he hadn't yet said he had a top end.....  ::)
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Offline Terry in Australia

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Re: 1978 F2 Inlet & Exhaust Valves in a1978 K8 ?
« Reply #10 on: July 19, 2010, 05:30:41 PM »
Ha ha, I knew I'd get a bite out of you mate! ;D
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I was feeling sorry for myself because I couldn't afford new bike boots, until I met a man with no legs.

So I said, "Hey mate, you haven't got any bike boots you don't need, do you?"

"Crazy is a very misunderstood term, it's a fine line that some of us can lean over and still keep our balance" (thanks RB550Four)
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