|
|
|
|
I have a 1977 honda cb 750k that I just got back together after installing new rings and carburetor kits. It seems to run ok at higher rpms and will idle around 1000 rpm, but if I jerk on the throttle it will die. It does it at low rpm all the time, and higher rpm it will act sluggish and then catch up. I have adjusted the air/fuel mixture screw like the manual says. Not sure if my problem is carburetor related or if it could be electrical.
While running the bike at 3000 rpm I lifted the contact points on 1/4 cylinder and the engine slowed to about 1200. Then did the same with 2/3 cylinder and the engine slowly died. Could something be wrong with my coil to the 2/3 cylinders? Is there a way to test it.
I have great compression, new carb insulators, and carb to air box insulators and have tested for vacuum leaks and have none. Contact breaker gap is correct. Timing is correct with a timing light.
I tried adjusting the mixture screws. I turned them all the way out and it didn't seem to make much of a change. Everything is stock on the bike.
It has an accelerator pump. I checked it while I had the carbs apart and had no cracks or holes in the diaphragm and it sprayed gas when I pumped on it. Then I checked the gap on the rod when it was back together and it all seems to be working correctly.
When the carbs were off I used a drill bit method to sync the carbs. I was waiting to get it back together before using a syncpro carb tuner. But I have not used it since it wasn't running well. Should I try using the snycpro now while its running like it is?
|
|
Administrator
|
You can test the coil with an Ohm meter. The factory service manual has detailed instructions on how to do this (you can download it for free from the manuals section at the top of the home page here). It sounds like you are starving for fuel. Are you running the stock airbox, or pods? Pods will make it run lean, and the jets will need to be changed. Also when you cleaned the carbs, did you remove the pressed in pilot jets to clean them? Unless you remove them they are almost impossible to clean. As for syncing the carbs, you are adjusting for vacuum, and it does not make any difference to the carb weather the cylinder is firing or not, it will still be creating vacuum, and be adjustable, so go on and adjust 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)
|
|
|
Ok, thanks. I have a service manual, so I will have to run that test. I have the original air box on it. I did not remove the pressed in jets, but I did boil the carbs in vinegar and ran wires down the holes. Then used an air compressor and all passages were clear. I will check the coils and snyc the carbs and see where Im at, and let you know. Thanks.
|
|
|
I tested the coils and they are OK. I then used the sync pro and synchronized the carbs. They seemed to be off quite a bit. But it is still running the same. It acts really lean. When its choked it has good throttle response, but wihhout being choked it stalls or dies.
|
|
Administrator
|
You have plugged pilot jets. You will need to remove them to properly clean them. If you use the search feature on the home page, for "removing pressed in pilot jets" you will find information on removing them.
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)
|
|
|
OK. That will be my next step then. Good thing there's over a foot of snow outside and I won't be riding any time soon. Once the pressed in jets are removed, can they be cleaned and re installed or do they have to be replaced?
|
|
|
Never mind that question. I found your post on removing them. What about the fuel inlet ( not sure the exact name) where the needle seats, should that be removed as well.
|
|
Administrator
|
I am not sure what you are referring to, but I will assume you are referring to the seat for the needle jet. On the keyhole carbs, it cannot be removed. Just clean it with some Q-tips and chrome polish.
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)
|
|
|
I got the carbs apart today. I need to get a tap and a screw yet to get them out. I am assuming the picture below is what the pilot jet is, where I'm pointing.  Also how can I test the accelerator pump. Where should gas come out when it pumps? 
|
|
Administrator
|
Yes that is the pilot jet. The accelerator pump nozzles are located in the back side of the carb where the intake boots attach. They are little brass fittings, and you should see gas squirting from them when you work the throttle.
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)
|
|
|
While having the bowl off the carb with the accelerator pump, I filled the bowl with gas and manually pushed the plunger down and nothing happens. Should I have gas squirting out somewhere or do I have a problem.
|
|
Administrator
|
On the accel pump. Gas goes in at the red arrow and will squirt out at the green. Watch your eyes. You'll have to work the pump several times if it's been dry before it'll prime.
|
|
|
OK. Thanks. I will have to see if its clogged or if the diaphram has a hole in it. It looked good when I put it together, but it doesn't squirt out at all.
|
|
Administrator
|
There are little, and I mean LITTLE check balls in the accelerator pump circuit that get corroded, and then they will not work. One is in the pump housing, and the other in the float bowel. To get them out, you drill a very tiny hole in the plastic plugs, and then screw a very small wood, or sheet metal screw into it, and pull it out. At that point the LITTLE check ball, and the even SMALLER spring will fly across the room into a very tiny black hole never to be seen again. If for some strange twist of fate you happen to catch them, you clean the ball by rolling it around on a piece of sand paper. Then you put them back in the holes, and press the plastic plugs back into place. You do not need to worry about the holes you drilled, they will not hurt anything.
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)
|
|
|
Ok, When I was cleaning them the first time I used an air compressor and it blew the plastic plug out of the the bowl check valve. I didn't realize that there was a bearing and spring in there and put the plastic plug back in. So Im guessing that I don't have the bearing or spring anymore in that side. So does this mean I will need a new bearing and spring, or can I do without one of them.
|
|
Administrator
|
Oh...bummer. Nah, gotta have all those parts in there for it to work. Sorry to say, but might be time to check out ebay.
|
|
|
That's what I was afraid of.... Thanks. The search begins.
|
|
|
So it turns out the ball and spring from the bowl side is gone. Any idea where to find new ones. I've looked all over with no success. The only thing I can think if is buying a accelerator pump kit that comes with the plate that goes over the diaphragm and use that ball and spring if its the same size. Not sure if that makes sense.
|
|
Administrator
|
If a rebuild kit will have those parts, then yeah! But i was thinking the ''kits'' were just a new diaphragm (never actually bought one,dont know). I don't have a spare #2 bowl it sell you. I imagine you can find one on ebay,but I havent looked.
|
|
|
I found found a kit at a local Honda shop and have it on order. It comes with the bottom plate, diaphragm and spring, and dust cover for 55 bucks. Kinda expensive when all I needed was 2 ten cent parts.
|
|
Locked
