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11 posts
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I am new and I'm trying to get my 81 custom running I have spark and fuel. Not sure what else to look at.
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1461 posts
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Have you done a compression test? Any motorcycle needs at least 100 psi for ignition.
Factory spec for my 81 is 170 +/- 28.
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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11 posts
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Not yet gonna try that in the morning. Thanks
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Administrator
10170 posts
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Do, you have fuel reaching the cylinders?
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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11 posts
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Have good compression no fuel going to cylinders 3 & 4. Dirty carbs maybe
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Administrator
10170 posts
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Sounds like it.
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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11 posts
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Well I found the problem. The timing chain came off! Not sure how to fix this guess I need a manaul
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Administrator
10170 posts
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It came off?  How? Did the bolts come out of the cam sprocket? Did the chain break? Or did a guide fail?
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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11 posts
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I'm guessing the guide failed it is off the crank sound like I have to tear motor apart.
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Administrator
1502 posts
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Which chain got loose: the short one between the 2 cams, or the long one from the crank to the exhaust cam? Pictures may help.
Some things to look at/look for:
You may be able to put it back on without tearing the engine apart. You will probably want to pull the engine from the frame to have better access. You will also want to know if something else got bent or broken when the chain let go. Valves, dents in piston tops, cams, other stuff.
However, you will want to know how/why the chain got off the cam. Possible causes: a VERY loose cam chain tensioner, bad cam chain guide, stretched chain. Once you find that out, it'll add to the list.
You need to count the cost of this repair vs. finding a used motor to replace it. Doing it yourself will save you lots in labor cost, but the parts ain't cheap.
Luke M
Used to have a 1979 CB750L, sold it as a parts bike, now riding a slightly modified 1984 VT700C. Network/Field Engineer. Central OH, USA, Earth, Sol System, Milky Way Galaxy, Universe.
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11 posts
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The long one it's not connected to the crank. Not sure how to fix or what has to come apart to get to it.
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11 posts
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The bad thing is I just bought this bike as a no start and wasn't expecting a timing chain issue
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Administrator
10170 posts
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That's a chance, you take. The DOHC bikes are known, for cam chain problems.
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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11 posts
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Well I found a tensioner set with guides cheap if I need it so I think I will tacle the project and get it running. I aprecciete all the advice it was alot of help
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Administrator
1502 posts
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It's possibly related to the single long chain between crankshaft and exhaust cam, and then another chain between the 2 cams. That's a lot of load for the chain: maybe too much? I'm not sure they updated that part of the valve train in later years, but maybe they missed it on the first year of DOHC.
Luke M
Used to have a 1979 CB750L, sold it as a parts bike, now riding a slightly modified 1984 VT700C. Network/Field Engineer. Central OH, USA, Earth, Sol System, Milky Way Galaxy, Universe.
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11 posts
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It's the long chain it failed debating repair or motor swap If I can find a motor close to were I live.
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Administrator
10170 posts
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Where do, you live?
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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1182 posts
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Hmm. I'm moving to Northville tomorrow. If I can get my bike running, I can possibly come down in a week to give you a hand if you want.
Turbos, Hondas, 4-bangers, what could go wrong?
 Shiny: [...] Considering the weather you've had to put up with I'd say you get an Iron Butt award and a Frozen Nipple trophy to go along with it. First time I've ever posted the word nipple... it ends here.
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11 posts
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I was just up that way looking at another bike.
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May 09, 2012; 12:57am
Locked
