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This post was updated on .
Hi all!
Long time listener, 1st time caller... I've been checking out this site the last few weeks, as I'm trying to get as much information as I can for my upcoming project. Decided to join the forum so I can ask questions, participate, and be encouraged.
Just a bit about my project: I bought my 77 CB750K about 15 years ago, it was in great shape and it worked great for the first year. My wife and I finished college and moved with our 1st child to where we are now (Coos Bay, Oregon - coincidence the initials are CB?) I took a job that required a one hour commute each way, so I was doing some PM on the bike, getting it ready for the task. While changing the drive chain, I somehow locked up the transmission - I don't remember at this point if I accidentally or intentionally moved the gear shifter, but end result is the bike locked up in first gear. I ended up parking it in the garage and always meant to get back to it, however, kids/job/other hobbies and responsibilities always took priority. The bike has followed us as we moved to new homes, and I thought about selling it, but always wanted to get back to it. Well, 14 years later, here we are. There is now some surface rust on a lot of the painted metal and chrome, the aluminum needs cleaned and polished, that stuck shifter still needs fixed, and I'm sure 14 years of inattention has taken its toll, so I am planning on completely tearing down the bike and going through everything. As the winter nights are going to be longer and my wife's patience getting shorter, I figured its a good time to get out of the house and to the shop to start this project. While I certainly hope to have it done by spring I am the king of unfinished projects - I'm on year 10 of my 3 year home remodel project ;)
I'll post some pics of the bike. The bike originally came with spoke rims, but a lady pulled out of a gas station in front of me and some hard braking/quick maneuver (loose spokes?) caused one of the spokes on the back wheel to tear from the rim. I bought the comstars, but only mounted the rear one. I no longer have the rear spoke rim, I think it went to the scrap yard. I don't recall what year/model the comstars were from, but the rear was a bit narrower than the spoke rim, so I used some hardened washers to fill the gaps. That's about all I've done to it. Anyway, here are the pics:
  
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Administrator
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Welcome. On your shifter being stuck, did you try cranking the engine, or turning the sprocket, and trying to shift while the engine was turning? Some times when the shaft is not turning the gears will not mesh, and cause just what you are describing.
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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Hi TOOLS. I really don't remember how I did it or what I was trying to accomplish when it jammed - just that I was in the middle of replacing the chain. I remember I was able to roughly shift between 1st and neutral for a bit, but while mashing on it trying to get it unjammed it stuck in 1st or 2nd. Should have slowed down and tried to find out what was wrong to fix it instead of trying to force it. Older, wiser, more patient, and have access to this site now! The shifter lever is now bent a little, so I'll have to replace it. I'm hoping I did not break anything or do major damage, but will see when I tear it down.
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Administrator
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When you say "tear down" what are you talking about? Surly you are not planning on taking the engine apart, I really doubt it needs rebuilt. Even though you bent the shift lever trying to shift it, I doubt you did any damage. As I said, the gears need to be turning, and the clutch disengaged to shift gears. If they are not turning the teethe will not mesh, and hit against each other preventing it from shifting.
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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Administrator
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Welcome in! And I agree with Tools. These transmission are tough as cut nails. I wouldn't tear it down unless you have seriously low compression.
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I was encouraged by the thought of not having to do a complete tear down - less work and money to get it running again is a good thing in anybody's book. It has just short of 29,000 miles on the odometer.
I went out to see if it would turn over with the kick-starter, but it wouldn't budge.
Thoughts? I'm pretty sure I read the solution in here somewhere... pb blaster in the cylinders and let it sit for a few days?
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Administrator
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If it was in gear with the chain on, then it probably would not be able to crank over. If it is the cylinders stuck, use a 50/50 mix of acetone, and ATF.
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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So if it is not the cylinders stuck, I should be able to crank it over with the chain removed? I will try that first before putting acetone/ATF in the cylinders. I won't be able to get to it until next week - I'm tied up at work and meetings for the next several days.
Thanks for the input, I'll let you know if I make any head way.
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I was able to spend a little time with the project today and made a little progress.
I started by loosening the cover behind the gear shift lever. This relieved pressure off of something, because as the cover became loose the shifter popped up. Now I can shift it between 1st and neutral. Yeah for small victories!!
The engine is still seized, so I removed the spark plugs and put a bit of acetone/ATF in each cylinder. I noted the bottom threads of the plug from #3 cylinder had a small amount of rust on them. I tried to look around the inside of the cylinder as best I could, but did not see any other rust in there.
Anyway, that's as far as I got before my wife wanted to go Christmas shopping.
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Administrator
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Every little bit gets ya one step closer.  Sounds like your shifter detent springs(s) or drum rotator fork might have messed up? Compare what it looks like now (before any more disassembly) to the FSM. Might give you an idea what's up.
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I have been side tracked with other projects and honey-do's for the last several weeks, but I was able to spend some time working on the bike today.
I had used the atf/acetone mix that Tools suggested, and it worked! The engine is finally unstuck! I also think I've got the stuck shifter figured out.
Now to start on the list of other things that need attention after 14 years of neglect...
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