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Hey guys, I am measuring the valve clearances on my 1980 cb750k DOHC and am reading the manual which says to rotate the camshaft and align the index mark on the right side of the exhaust camshaft with the cylinder head mating surface. My question is, which index mark is it?
This is the right side of the exhaust camshaft and it has these two index marks.
 Now this is the left side of the same camshaft and it has the two larger marks on them.
 When measuring the valve clearances, do I basically just want each camshaft lobe to be pointing straight up? One somebody on YouTube said to make sure the camshaft lobes are pointing at the spark plugs etc. What say you? Sorry guys for the noob questions, I am trying to learn. Thanks!
1980 cb750k
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Administrator
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I have never messed with the DOHC CB 750, but on the Kawasaki DOHC bikes, you want the cam lobes to be pointing slightly towards each other. I would suspect that the two indents on the left side of the cam should be at 12:00 and 6:00 if that is where the cam lobe is off the valve lifter bucket.
TOOLS
Life is not about the number of breaths, you take, but the moments that take your breath away.
I don't have an anger problem. I have an idiot problem. Hank Hill
Never confuse education for intelligence.
Happiness is a belt fed weapon.
I just can't imagine what could go wrong.
No fire? No explosions? So whats the point of your story?
Those who are too smart to engage in politics are punished by being governed by those who are dumber. ~Plato
It couldn't be done, but the darn fool didn't know it, and did it anyway.
We all got problems. Ksharp
I like vintage bikes because they take me away from the clutter of technology that I work with everyday and back to a simpler time of mechanical elegance and simplicity.. "ninadm"
Darkwing Duck: The worst part of public transportation is the Public.
"That is awesome shit there" Re-Run
"Fear nothing, attack everything" Eric Berry
" Oh, you read that on the internet? Clearly it IS a massive problem. Of course it CAN’t be normal operation."
1976 CB 750-A X 2
1977 CB 750-A X 4
1977 CB 750-K
1976 CB 750 F
1981 CB 750
1966 Kawasaki SG 250
1981 KZ 750 LTD
1973 CB 350
1979 CM 185 Twinstar
1982 Honda XL 80
South of Eden (Kansas City MO)
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Administrator
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I just rotate the cam to the heel of the lobe , the opposite end of what opens the valve. So with a bucket and shim setup like you have, I'd just point the pointy part of the lobe straight up.
I never saw the need for reference marks on this. Just measure your gap when the cam is "off" the shim.
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Thanks guys. I'll do that. Sometimes I just need things explained to me like a four year old ;).
On Mar 25, 2016 8:22 AM, "shinyribs [via Honda CB750'S]" < [hidden email]> wrote:
I just rotate the cam to the heel of the lobe , the opposite end of what opens the valve. So with a bucket and shim setup like you have, I'd just point the pointy part of the lobe straight up.
I never saw the need for reference marks on this. Just measure your gap when the cam is "off" the shim.
A free people ought not only be armed and disciplined, but they should have sufficient arms and ammunition to maintain a status of independence from any who might attempt to abuse them, which would include their own government.~George Washington
1980 cb750k
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Administrator
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Nah, you're smarter than that. OEM's will spell things out to the Nth degree in their manuals, and some people love that. But simple is better.
Somewhere on here sometime mentioned finding these shims at a local auto parts store listed as Toyota items, IIRC. Check that out so you don't end up overpaying if you need shims. They can be incredibly expensive through some online vendors.
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Excellent Shiny, thanks. I look for that.
On Mar 25, 2016 10:27 AM, "shinyribs [via Honda CB750'S]" < [hidden email]> wrote:
Nah, you're smarter than that. OEM's will spell things out to the Nth degree in their manuals, and some people love that. But simple is better.
Somewhere on here sometime mentioned finding these shims at a local auto parts store listed as Toyota items, IIRC. Check that out so you don't end up overpaying if you need shims. They can be incredibly expensive through some online vendors.
A free people ought not only be armed and disciplined, but they should have sufficient arms and ammunition to maintain a status of independence from any who might attempt to abuse them, which would include their own government.~George Washington
1980 cb750k
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Okay so I measured the clearances and now I need to measure the shims and come up with the sizes I need. Thanks for the guidance. I have read that many people recommend a clearance on .005" rather than the .003" that the FSM recommends. They mention valve cooling at the cost a slight performance to be their reason. Is that right or should I just stick with FSM recommendations?
1980 cb750k
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Administrator
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That would allow the valve to stay in contact with the valve seat longer, which is how it is cooled, but I would stick with the factory specs.
TOOLS
Life is not about the number of breaths, you take, but the moments that take your breath away.
I don't have an anger problem. I have an idiot problem. Hank Hill
Never confuse education for intelligence.
Happiness is a belt fed weapon.
I just can't imagine what could go wrong.
No fire? No explosions? So whats the point of your story?
Those who are too smart to engage in politics are punished by being governed by those who are dumber. ~Plato
It couldn't be done, but the darn fool didn't know it, and did it anyway.
We all got problems. Ksharp
I like vintage bikes because they take me away from the clutter of technology that I work with everyday and back to a simpler time of mechanical elegance and simplicity.. "ninadm"
Darkwing Duck: The worst part of public transportation is the Public.
"That is awesome shit there" Re-Run
"Fear nothing, attack everything" Eric Berry
" Oh, you read that on the internet? Clearly it IS a massive problem. Of course it CAN’t be normal operation."
1976 CB 750-A X 2
1977 CB 750-A X 4
1977 CB 750-K
1976 CB 750 F
1981 CB 750
1966 Kawasaki SG 250
1981 KZ 750 LTD
1973 CB 350
1979 CM 185 Twinstar
1982 Honda XL 80
South of Eden (Kansas City MO)
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Administrator
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Can never go wrong with Honda specs. But, lots of guys have been running .005" with no bad side affects. If I had a valve at .005" I wouldn't bother reshimming it to .003"
I had a thought, though. You'll need to sort out your cam marks eventually. Actually, you needed to already. You need those marks to verify that both cams and the crank are all timed correctly with each other, or you could be crashing valves in to pistons on start-up. It's been awhile since I've done that job, but I'll look at the FSM to see if it sparks any memories.
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Well as far as the cam timing I've got that taken care of. I made sure the two dots on the cam sprocket were horizontal and the two marks on the left side were horizontal with the lobes of cylinder one pointing towards the spark plugs.
On Mar 25, 2016 8:27 PM, "shinyribs [via Honda CB750'S]" < [hidden email]> wrote:
Can never go wrong with Honda specs. But, lots of guys have been running .005" with no bad side affects. If I had a valve at .005" I wouldn't bother reshimming it to .003"
I had a thought, though. You'll need to sort out your cam marks eventually. Actually, you needed to already. You need those marks to verify that both cams and the crank are all timed correctly with each other, or you could be crashing valves in to pistons on start-up. It's been awhile since I've done that job, but I'll look at the FSM to see if it sparks any memories.
A free people ought not only be armed and disciplined, but they should have sufficient arms and ammunition to maintain a status of independence from any who might attempt to abuse them, which would include their own government.~George Washington
1980 cb750k
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