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Well iv done a complete novice overhaul on this bike- the 78 sohc iv replaced points and condensers, cleaned the carburetors, (mainly just the jets and the boats), and switched out the alternator cover. Now im at the point where iv gotten it running a couple of times, once down the block but iv got so many bugs im not sure what the issue is. Pre-carb clean, at any kind of low idle, the bike will just die. At one point i got into 3rd gear, and got no acceleration at all, but even a kind of draw back. Possibly whole nother issue.
At one point after the carb cleaning, i got it running for a little while, (only runs on choke even after warm up) and it unexpectedly died. I felt the exhaust to find that only 3 and 4 were running strangely enough, which kind of rules out coils due to the chamber placement. Right now i adjusted the pilot screws on the carbs to find that when trying to get it started, only cylinder 1 is running/ only pipe to heat up. So right now im completely overloaded with issues and possibilities.
Possible issues iv concieved are the cable adjustments after the carb cleaning and not setting them EXACTLY as they were, switching around the jets, seemingly intermittent gas flow issue, and possibly complications due to some rust in the gas tank. Im just not sure where to start, and any direction would be HIGHLY appreciated. Thanks
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Administrator
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Welcome to the forum. Your pilot jets are plugged. They are the press in ones, and have a very, very, very tiny hole. You need to gently pull them out, and run a very small wire through them. That will cure most of your problems right now with it running. Also check to make sure your accelerator pump is working. You should be able to see gas spray in the carbs when, you twist the throttle by looking in the inlet side of the carbs. There are two very, very, very tiny check balls, and springs in that circuit. It does not take much to plug them up.
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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My first guess is what Tools said.
If they're not plugged, I'd say to take a look at the auto-petcock, but I'm not sure if the 78 had one or it was just the dohc bikes (79+). If the auto-petcock is rotten that could be a reason its starved for fuel.
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.
My cb750 video site
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Thanks for the advice! The verdict was indeed a rusty gas tank, and a clogged petcock creating intermittent fuel issues. Now im noticing the issue that not all cylinders seem to be firing properly, and the fuel mix smells very rich from cylinders 1 and 2. It ran ok after warming up, but i got the feeling that 1 of the four was not quite running right- more of a thud than a chug. Not quite sure what to tune here- seems to be more than the idle screws, though they're the only thing that i've adjusted.
on a side issue, when idling around a corner the whole bike died, and i traced it to the lower of the three fuses on the side. I attribute this to a short, as there is a partially exposed wire that is part of the main starter circuit.
So i got a couple more kinks to work out, but you all have been Hugely helpful with my progress so far.
Just spitballing for any extra tips or advice. Thanks again in advance- cheers!
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Administrator
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Replace those fuses with the wire in blade type fuse holders. Then get a blade type 30amp breaker, for the main.
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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what will this help? also why up the amperage- seems counter intuitive
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Hey man,
If I were to take a guess at what tools was suggesting, is that by putting it higher amp fuses, they won't burn, but the breaker will, and all you need to get the breaker to work again is flip the switch. I am assuming this must be a preference of his when dealing with electrical issues, rather than keeping a stock of fuses on hand. The current rating for the breaker should be higher than an independent fuse, because the fuses are in parallel, therefore only 'seeing' part of the overall current, unlike if you were to put this breaker in series with the battery and the rest of the electrical system on the bike. which ALL of the current would flow through.
Hope this helps!
~ba5sKing
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