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1982 cb750f
So sometimes the bike runs great right out of the garage, sometimes it seems to take a bit to warm up, then is fine, and sometimes it runs like shit. It will rev in neutral, but then it has no power when you try and take off. You have to slip the clutch to take off (quite exciting when you're far from home). Sometimes it has no high rpm throttle response, and it will not rev past say 6k. Other times it has loads of power. The choke doesn't seem to effect it, so I'm thinking electrical.
When this happens, it also won't idle, I have to crack the throttle to keep it running. Then maybe 3 miles down the road, it will start to idle fine. I originally thought I had a vacuum leak, but the fact that it comes and goes doesn't make sense to me.
Before I start half hazardly checking things, I thought I'd post here. Given that it's a sporadic condition, I'm not sure where to start. Thanks for the help!
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Administrator
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Is this a recent issue? Or have you gone through multiple tanks of fuel and it still happens?
Have you noticed that it runs better at certain temps than others, as in air temp?
Some of the symptoms sound like it is running lean. So at warmer temps, air is not as dense and the bike would be able to run a bit richer. Lower temps, air is denser and that would make the mix leaner.
I would check the plugs and see what they look like but it sounds like a lean condition.
The ride IS the adventure. The destination is just to get gas!
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I'm in Dallas so it's always 100*. I run sea foam and it's happened on multiple tanks. I assumed the choke would help if it's running lean, and it doesn't seem to help. I'll pull the plugs and start there.
Sent from my iPhone On Sep 1, 2014, at 1:06 PM, "Re-run [via Honda CB750'S]" < [hidden email]> wrote:
Is this a recent issue? Or have you gone through multiple tanks of fuel and it still happens?
Have you noticed that it runs better at certain temps than others, as in air temp?
Some of the symptoms sound like it is running lean. So at warmer temps, air is not as dense and the bike would be able to run a bit richer. Lower temps, air is denser and that would make the mix leaner.
I would check the plugs and see what they look like but it sounds like a lean condition.
The ride IS the adventure. The destination is just to get gas!
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So now I'm really confused, the plugs were dirty, but not overly rich. I went for a ride and came back, and it appears that #3 and #4 aren't firing correctly. I obviously knew something wasn't right as I was low on power. These two pipes I could touch, whereas #1 and #2 were very hot. I don't understand how these two cylinders could not fire, as they aren't on the same coil.
I pulled the coils and tested them per the manual, I am getting 3.2 OHMs on the primary side, but not getting any reading on either on the secondary. I had good contact, and I checked multiple times. Also I grounded out #4 before removing the coils, and the spark was weak at best.
This makes absolutely no sense to me. How can each coil run one cylinder in it's bank, but not both. Any help would be appreciated. Also, the bike started recently sporadically missing before it lost power all together.
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I'm starting to really lose my mind. Thought I'd check again, and now I'm getting about 13k on the secondary side of both coils. Is it possible that now that they are 100% cool they are both testing fine, but that is why my issues seem to be so sporadic?
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Administrator
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It's not your ignition system, it's your carbs.
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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Any suggestions what to look for? Carbs were rebuilt and synced. It's ran fine for months then these issues started up. I've started by checking for vacuum leaks, and resolved that. It's obviously #3 and #4 as those are the cold cylinders.
Sent from my iPhone On Sep 2, 2014, at 11:25 PM, "TOOLS1 [via Honda CB750'S]" < [hidden email]> wrote:
It's not your ignition system, it's your carbs.
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.
1976 CB 750-A X 2
1977 CB 750-A X 2
1977 CB 750-K X 2
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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Your jets are probably plugged. Just look for dirt in them. Even could be rubber from deteriorating fuel lines.
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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Fixed! I'm not sure if I should feel fortunate or embarrassed. So after tearing the carbs off last night and inspecting and cleaning all of them (they were already spotless), and getting everything put back together, I got it to start but still no gas in #3 or #4 bowls. I then checked for a hung float, and everything was within clearance. After some careful thought, the issue was..... a crushed in-line fuel filter. It appeared that the PO crushed the inlet/outlets and it was just trickling and starving two cylinders.
Thanks for all the help, maybe this thread will help someone else someday.
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