Topic: Fastest cb750A ever?

[gschuld]

Billy, do you remember what times the RC automatic ran.  Low 10s I think I remember.  There was a second article mention of the auto that I believe you showed me that had a time on it.

Ring any bells?

[kmb69]

Forgive me if this has been answered before, but would it be possible to fit a "trans brake" to the Auto? As I understand it, the brake operates two gears at the same time, effectively locking the trans, without relying on the rear wheel brake to prevent the vehicle from rolling through the beams..

All transbrakes that I know of block the trans into first and reverse. Could there be another way? Not that I can think of,  but there are certainly smarter minds than me out there. 

Maybe, but the Auto doesn't have a reverse of course and the switching valve for the 2 speeds is mechanical versus solenoids. Engaging both forward gears simultaneously might do the trick but would certainly take some engineering.

I have always suspected that some similar scenario of the low clutch not disengaging properly or at least both clutches engaged at the same time may have caused Sam's wreck. I think the consensus is that Sam had a brain fart and grabbed the rear brake on the left handlebar but I have always been suspect of the trans. We'll probably never know for sure since Dear Sammie can't remember the sequence of events.

Ultimately, it won't work for me as a trans brake since I am eliminating the clutches and will use a serious rear brake similar to what Bill describes.

[underdog]

    No clutches? That's an interesting idea. So the converter handles all the slippage, but that shift willl be awful brutal. In the early days,  we would crank up the line pressure and that got kind of rough. Then transbrakes came along and broke everything else left in the driveline. Since there is a seperate regulator, how about raising pressure there or maybe a hi/lo pressure solenoid?

[kmb69]

On the stock tranny, both gear sets are always engaged. It's only the clutches engaged/disengaged that "changes" gears.

[scottly]

On the stock tranny, both gear sets are always engaged. It's only the clutches engaged/disengaged that "changes" gears.

How is your trans going to work with no clutches??

[scottly]

I think the consensus is that Sam had a brain fart and grabbed the rear brake on the left handlebar

No, this was a theory that I proposed, and it was not well received.... 

[kmb69]

I think the consensus is that Sam had a brain fart and grabbed the rear brake on the left handlebar

No, this was a theory that I proposed, and it was not well received....

Yes, I know. But after spending as much time as I have in these transmissions, I think that may be the case. Muscle memory!
Also, Mike did the tear down and could not find any forensic evidence to suggest otherwise. Their design is essentially fail proof.
It's pretty kool to be able to launch by releasing the rear brake like a clutch but the downside can be potentially big trouble.
Pretty sure Billy is planning to remove the temptation on the rebuild. I know I am after riding a clutch bike all my life.

[kmb69]

On the stock tranny, both gear sets are always engaged. It's only the clutches engaged/disengaged that "changes" gears.

How is your trans going to work with no clutches??

A KMS style tranny like Bill Hahn Sr. (RIP) designed years ago. It is air shifted via a plunger rod through the countershaft.

[madmtnmotors]

I think the consensus is that Sam had a brain fart and grabbed the rear brake on the left handlebar

No, this was a theory that I proposed, and it was not well received....

Yes, I know. But after spending as much time as I have in these transmissions, I think that may be the case. Muscle memory!
Also, Mike did the tear down and could not find any forensic evidence to suggest otherwise. Their design is essentially fail proof.
It's pretty kool to be able to launch by releasing the rear brake like a clutch but the downside can be potentially big trouble.
Pretty sure Billy is planning to remove the temptation on the rebuild. I know I am after riding a clutch bike all my life.

From the grainy video I saw the rear of the bike was snapping side to side as if the rear wheel was locked up. I would expect this was either brake, engine, or transmission. The engine was (somewhat) ruled out by Billy in subsequent test-n-tune and possibly competition passes if I remember correctly. There was some behavior that led Bill to take the bike out of service and have the engine thoroughly examined by Mike.

I always wondered about the "muscle memory" thing. I have a little Coleman CT200U that I use as a pit bike. The set up for these directs the placement of the single brake lever (rear drum) to be on the left handlebar. This was very unnatural for me and I quickly switched the location of this brake lever to the right side where it belongs. I wonder if a "linked brake" connecting both the front and rear brake would be an option? 

[dragracer]

Bill Benton, if you have an extra stock converter. I'd be willing to take it to a well know shop in Columbia that specializes in rebuilding and modifying converters. He builds race converters for the drag car it's and has a great reputation. They reworked  the converter for my fully auto VW dragster.

[jgger]

Wilbur, back in the 70's they made such a devise for dirt bikes. It was called a "Diffbrake" they tried to market it to us Desert guys, but it never caught on.

[scottly]

My first "muscle memory" event came on the first test ride of my '53 BSA 650, which I assembled from a basket case. No matter how hard I pressed on the shifter, the rear brake wouldn't work. I thought it was odd, as I was cognizant of the shifter/brake reversal when I started out, but completely forgot about it when I had to slow down at the end of a dead-end street...

[spotty]

had the same muscle memory thing going on when i rode a friends auto italjet dragster scooter ( the hot one with the hub centre steering, stupidly tuned motor etc ) got half way down the street and my brain told me it was revving quite enough so i pulled the clutch in to change gears, problem was the clutch was the back brake and there was no gear lever to use either.....
despite its little wheels it has remarkable effective brakes and i nearly went over the handlebars
i rode it back quite carefully and gave it back before i broke it

[Sam Green Racing]

OK guys, lets get something straight here, there was nothing wrong with my brain until I hit the track. (brain fart).
Why would I suddenly think I had a clutch, when it was the only bike I had been riding for 5 years ?
Why would I want to stop in the middle of the track and hold up proceedings by putting on either brakes ?
All I was trying to do, was to roll as far as I could in the hope of saving to push it to the first exit.
The back wheel was locked on well before the 8th and I lost control going through the 8th before low siding just after it.
The reason Bill pulled the bike from service was that it was making a noise when he next started it up.

Sam.

[POPS 911]

You run 10 anything on a CB750A SOHC and I will be standing at the ticket booth with 5 new $100 bills to put in your hand with that time ticket.  Talk is cheap but the ticket with 10's on 1320' on a 750A SOHC = LET ME KNOW WHEN AND WHERE this is going to happen in USA , I do-not have a pass port to travel out of my neck of the woods USA.

POPS BK911

[kmb69]

OK guys, lets get something straight here, there was nothing wrong with my brain until I hit the track. (brain fart).
Why would I suddenly think I had a clutch, when it was the only bike I had been riding for 5 years ?
Why would I want to stop in the middle of the track and hold up proceedings by putting on either brakes ?
All I was trying to do, was to roll as far as I could in the hope of saving to push it to the first exit.
The back wheel was locked on well before the 8th and I lost control going through the 8th before low siding just after it.
The reason Bill pulled the bike from service was that it was making a noise when he next started it up.

Sam.

Did I say "brain fart"? I meant "old fart"!     
Like I said, I always suspected the transmission.
If the low clutch did not release when the high clutch was engaged, in theory, it would lock the tranny.
But it's one of them "whodunits", "what happened" we'll probably never know for sure.
Luv u Sammie! 

[calj737]

OK guys, lets get something straight here, there was nothing wrong with my brain until I hit the track. (brain fart).
Why would I suddenly think I had a clutch, when it was the only bike I had been riding for 5 years ?
Why would I want to stop in the middle of the track and hold up proceedings by putting on either brakes ?
All I was trying to do, was to roll as far as I could in the hope of saving to push it to the first exit.
The back wheel was locked on well before the 8th and I lost control going through the 8th before low siding just after it.
The reason Bill pulled the bike from service was that it was making a noise when he next started it up.

Sam.

As Keith said, probably never know what happened. The ONLY thing that matters is that you, Sam, survived and live to see another day.  I know we are all eternally grateful for that.

[madmtnmotors]

As Keith said, probably never know what happened. The ONLY thing that matters is that you, Sam, survived and live to see another day.  I know we are all eternally grateful for that.

Amen.

[Bill/BentON Racing]

Yep, we'll never KNOW...... As Cal and others stated, doesn't matter, we still got Sam! That's what matters! Bill

[kmb69]

Yep, we'll never KNOW...... As Cal and others stated, doesn't matter, we still got Sam! That's what matters! Bill

Amen.

[Medyo Bastos]

OK guys, lets get something straight here, there was nothing wrong with my brain until I hit the track. (brain fart).
Why would I suddenly think I had a clutch, when it was the only bike I had been riding for 5 years ?
Why would I want to stop in the middle of the track and hold up proceedings by putting on either brakes ?
All I was trying to do, was to roll as far as I could in the hope of saving to push it to the first exit.
The back wheel was locked on well before the 8th and I lost control going through the 8th before low siding just after it.
The reason Bill pulled the bike from service was that it was making a noise when he next started it up.

Sam.

Let me ask a dumb question, was the chain still on both sprockets when the bike finally stopped?


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[kmb69]

.....
Let me ask a dumb question, was the chain still on both sprockets when the bike finally stopped?
.....

Yes sir.

[scottly]

Why would I suddenly think I had a clutch, when it was the only bike I had been riding for 5 years ?

Maybe because you launched the auto just like you would have a clutch bike, by releasing the left hand lever? If you were on a clutch bike and lost power mid-track, the natural instinct would be to yank in the "clutch" lever. The only reason it matters is no one wants to see this happen to anyone else.
Love you Sam.
Scott