Vintage and Classic Hondas

timing marks

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bobberguy
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timing marks

bobberguy
Hey guys just bought a cb750 turning it in to a bobber bike wont fire just cranks and cranks fast did a compression test one side was over 100psi other was at 60 i think the timings off but i don't know what timing marks go by if you guys have any suggestions or tips i would appreciate it thanks.
TOOLS1
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Re: timing marks

TOOLS1
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Ignition timing will not affect compression. Did you also do a wet compression check?
To find the timing marks however, you can download the factory service manual for free from the home page here.
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)
seestheday
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Re: timing marks

seestheday
In reply to this post by bobberguy
Ya, I wouldn't bother with fixing the timing until you address your compression issue.  No bike will run with less than 100 psi compression.  Ideal for the DOHC bikes is about 170 psi but 150 psi is more realistic.
1981 CB750K with 900 cams
90K KM's, rebuilt head, rebuilt carbs, upgraded valve stem seals

My wife's recipe website that I'm trying to help promote: Strawberries for supper. Yes, I am a lucky man.

shinyribs
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Re: timing marks

shinyribs
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I'm with Tools and Sees'. You'll have to address the compression issue first. I'd start by adjusting the valves.

BTW,what year bike are you working on?
bobberguy
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Re: timing marks

bobberguy
Its an 81 i checked the timing it was 1 tooth off i just dont know where to go from here tho and i dont want to sink tons of money into this thing even tho it only has 16000 miles on it
seestheday
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Re: timing marks

seestheday
I doubt it will cost you a lot of money, but it might take you a ton of time.

If you want more help you're going to have to give us more details .

We still don't know if it is an SOHC (pre 79) or a DOHC (post 79).  There are dramatic differences between the models.

With compression at 60psi you might need new rings, or just have a stuck valve.  There are a lot of things it could be at this point.
1981 CB750K with 900 cams
90K KM's, rebuilt head, rebuilt carbs, upgraded valve stem seals

My wife's recipe website that I'm trying to help promote: Strawberries for supper. Yes, I am a lucky man.

TOOLS1
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Re: timing marks

TOOLS1
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In reply to this post by bobberguy
Are you talking about cam timing, or ignition timing? Big difference!
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)
bobberguy
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Re: timing marks

bobberguy
Im sorry i should have specified cam timing it was one tooth off and its the DOHC
seestheday
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Re: timing marks

seestheday
Doing a leak down test should be able to tell you if it's valves or rings. I'm betting on rings. You're going to need to pull the head, possibly the cylinder block.

It won't take a lot of money, but it could take a lot of time depending on your experience.
1981 CB750K with 900 cams
90K KM's, rebuilt head, rebuilt carbs, upgraded valve stem seals

My wife's recipe website that I'm trying to help promote: Strawberries for supper. Yes, I am a lucky man.

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