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Speed Wobbles.
I was taking a corner at a fairly high speed and my bike started to suddenly wobble bad. I clamped down on the bars to fight it, rolled the throttle off and tried to straighten up the bike as much as I could given that there was oncoming traffic and I didn't want to cross that double yellow line.
The tires are two years old and in good shape. I will be checking my steering stem bearings soon, as well as making sure that the rim is true and there are no flat spots.
That was definitely the most scared I've been riding a bike. I'm still thinking about it. No more corners like that is a given, but I also need to fix the issue that caused it.
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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Administrator
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Glad you came out OK, but next time give it 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)
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Administrator
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Where did you feel the wobble start? Have you taken corners like this before?
You may also want to check to make sure your swingarm bushings are not worn. Since you will be checking the back rim, just grab the wheel and move it from side to side and observe what the swingarm does. If it moves at all other than up and down, the bushings are in need of replacement.
Check for loose spokes too since you are checking for roundness and trueness.
If everything comes up ok, made the shocks or forks are having issues.
The ride IS the adventure. The destination is just to get gas!
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TOOLS1 wrote
Glad you came out OK, but next time give it throttle.
TOOLS
There was a car in front of me. Speeding up wasn't an option. 
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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Re-run wrote
Where did you feel the wobble start? Have you taken corners like this before?
I think it started when I started to decelerate a little bit. It happened really fast so I'm a little fuzzy on the details. I don't remember touching the brakes, just rolling off the throttle a little.
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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Administrator
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I wonder if your fork fluid is low on 1 side. When you let off, weight transferred forward as you know and maybe 1 side did not dampen enough.
The ride IS the adventure. The destination is just to get gas!
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Administrator
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seestheday wrote
TOOLS1 wrote
Glad you came out OK, but next time give it throttle.
TOOLS
There was a car in front of me. Speeding up wasn't an option.
Tailgating?  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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Tailgating? TOOLS
He was probably 5 car lengths in front of me at the beginning of the turn but he was braking to go around it. Going into it he was going faster than I was (pulling away from me).
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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Administrator
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Glad you came out of it ok and were able to regain control.  Any corner a car can go through will be a breeze at the same speeds for your bike. I'd definitely take a look at loose suspension components or even the road surface there to see whats.
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whew!
"The thing about quotes on the Internet is you cannot confirm their validity" - Abraham Lincoln
"Men occasionally stumble over the truth, but most of them pick themselves up and hurry off as if nothing ever happened." - Winston S. Churchill
Most motorcyclists live more in five minutes than other people do in their entire lives.
when you mix religion with politics you get politics
people say I'm condescending (that means I talk down to people)
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I was able to reproduce the problem under much more controlled conditions.
Hard cornering at normal speeds - constant speed - no issue
Hard cornering at higher speeds - constant speed - no issue
Hard cornering at normal speeds - accelerating - no issue
Hard cornering at higher speeds - accelerating - no issue
Hard cornering at normal speeds - decelerating - no issue
Hard cornering at higher speeds - decelerating - wobbleWhile in a straight line or slight corner no amount of accelerating or decelerating produced any wobble.
Once I get up to a high enough speed and do a hard corner I feel a wobble even if I just roll off the throttle a little bit. Get back on the throttle and the wobble disappears. It only happened while cornering. Happened on several different roads, so I can eliminate that variable.
I won't have time for at least a week before I can really tear apart the bike, but I will definitely get to the bottom of this.
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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Administrator
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You have just discovered what a lot of riders have known for years. De-accelerating at speed in a corner produces wobble, and accelerating pulls you out of it. I try to always make sure I have room in a corner to accelerate, or maintain a constant speed through 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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Administrator
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Yep, gear down and let her eat. Letting off always feels gross. Its the whole gyroscope things.
Hey, if you think it feels bad with the rolling stock you have on your bike, try it with a lightweight set of 17's. It can get down right stupid!
The more rpms you can hold in a corner the more stable it will feel. Go experiment and see what you think.
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Sorry, I don't understand the gyroscope issue. The more I think about this I believe it is a suspension related one (caused by a rapid change in suspension compression). Are you referring to the difference in forces caused by the crankshaft going from spinning fast to spinning more slowly? I don't see how it will be large enough.
Sorry, I may be reading too much into this. I have a background in physics so when I don't understand something related to it I really want to know.
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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Administrator
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Try going in to a hard turn at, lets say, 60 MPH in second gear. The rpms will be high and constant and it will feel nice, smooth and predictable. Take the exact same turn at the exact same speed but pull in the clutch and just coast through. It'll be a completely different feel.
Everything about bikes are gyroscopic. Its the only reason the go down the road at all. Of course, I know you know that. But it all makes a difference.
Rapid unloading / loading of the suspension can play a part as well, like you say. Wouldn't hurt to inspect the bike, but if it only does it on hard decel it sounds pretty familiar.
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Locked
