Topic: ET, matic vs clutch

[Don R]

 Any guesses what a cb750 big bore dragbike would give away being an automatic versus a clutch trans?  1/8 mile or 1/4 mile. I guess I know what the quickest clutch bike super eliminator ET is, what's the quickest 750A ET with a similar top end? Bill B probably already knows the answer. 

[MRieck]

Any guesses what a cb750 big bore dragbike would give away being an automatic versus a clutch trans?  1/8 mile or 1/4 mile. I guess I know what the quickest clutch bike super eliminator ET is, what's the quickest 750A ET with a similar top end? Bill B probably already knows the answer. 

Don....don't get me started. Really!

[Don R]

  The pot don't stink if you don't stir it. lol. 

[Sam Green Racing]

  The pot don't stink if you don't stir it. lol.

Stinky Sam here Don, lol.

It's something you'll never find out mate. No one has ever taken a CB750A to the limit in terms of trying to make it the quickest.
In 1980, a CB750K blown nitro bike was the first bike to run in the 7s in the UK, how many people do you know that have supercharged an automatic and run it on nitro ?
Over to you you $hit stirrer. lol.

Sam.

[Don R]

 The only reason I asked is because I was reading about fast cb750 drag bikes using up transmissions. I am aware of the torque converter limitations caused by a cast aluminum turbine. Clearances may be changed but not fin angles.
 
  In the case of the Chevrolet powerglides, someone realized an 8" Opel torque converter could be used in a two speed big car transmission case, making a high stall speed. We probably won't ever have the luxury of high demand bringing the aftermarket in or even luckily finding a better converter that works and fits. 
 
 

[PeWe]

  The pot don't stink if you don't stir it. lol.

Stinky Sam here Don, lol.

It's something you'll never find out mate. No one has ever taken a CB750A to the limit in terms of trying to make it the quickest.
In 1980, a CB750K blown nitro bike was the first bike to run in the 7s in the UK, how many people do you know that have supercharged an automatic and run it on nitro ?
Over to you you $hit stirrer. lol.

Sam.

I had to search since a local guy not far from me had a fast CB750 for many years ago. Same guy, Stefan Reisten.

I bought a set of strong rods said to be from his engine on a part meet early or mid 80's.
Lost when moved to my house 2004.
Also found this older post here.
http://forums.sohc4.net/index.php?topic=115272.0

He used a bigger Yamaha engine after the CB750.

Maybe he used same tuning shop as I did and still do. I have to ask the mechanic/tune still working (I have had ideas to gas port  my 71.25mm pistons for my billet block since the tuner mentioned it. Holes from the sides).

That shop's  (Motospeed) owner was a drag racer too, Pro Bike.

About the commercial on bike. "Rasten" was a popular burger, hot dog restaurant in the 70-80's.
Västerås is the name of my town where I live.
Stefan Reisten lived in a small village north of Västerås in the 80's.  Maybe still do.
Same village I have visited a Harley tuner, former HD drag racer for dynos the last 3 years.

We other bikers in Västerås were very proud of those to dragracers early 80's.

Edit: How to pronounce Västerås. Wovels ä, å.
- ä as in west
- å as the beginning of Auburn.
We have an wovel ö too. As jerk.

[Don R]

 Actually, I was wondering the difference between two equal top ends, exhausts and carbs on an auto bike versus a 5 speed bike. Let's say ported and cammed 836's for the sake of argument. I assume the A would have a slightly modified converter and the manual has a good clutch.

 Maybe I need to invent a cb750 trans brake. L0L!
 
   

[dragracer]

Actually, I was wondering the difference between two equal top ends, exhausts and carbs on an auto bike versus a 5 speed bike. Let's say ported and cammed 836's for the sake of argument. I assume the A would have a slightly modified converter and the manual has a good clutch.

 Maybe I need to invent a cb750 trans brake. L0L!
 
   

Bill Benton and Jim French can tell you all you need to know about modified torque converters for an A. They had one done at a converter shop in Houston.  It seemed to make a noticeable difference in stall rpms. The biggest issue was having a decent braking system to hold on the line when the rpms came in against the stall. The next problem was a nerve raking bog once the brake was released and the throttle pinned. After some painstaking work by all, they figure out how to make the,Suzuki CV carbs work okay. It entailed a ton of jetting changes and eventually modifying the springs on the slides to allow a quicker opening at WOT. Lots of frustration surrounded the carb issue. It's a major sore spot for all involved so I'm going to leave that issue alone for now. 🤪

[Don R]

  If there was a converter with a steel turbine, the fins could be laid down and re-brazed. But alas, they're cast aluminum so all that can be done it cut them open and change the gap between the turbines. If a real transmission guy thought there were more than one or two of us interested I'm sure a lot more could be done.

 Edit, J Weeks has had one modified by milling out fins and replacing them with welded replacements.

[MRieck]

Actually, I was wondering the difference between two equal top ends, exhausts and carbs on an auto bike versus a 5 speed bike. Let's say ported and cammed 836's for the sake of argument. I assume the A would have a slightly modified converter and the manual has a good clutch.

 Maybe I need to invent a cb750 trans brake. L0L!
 
   

Bill Benton and Jim French can tell you all you need to know about modified torque converters for an A. They had one done at a converter shop in Houston.  It seemed to make a noticeable difference in stall rpms. The biggest issue was having a decent braking system to hold on the line when the rpms came in against the stall. The next problem was a nerve raking bog once the brake was released and the throttle pinned. After some painstaking work by all, they figure out how to make the,Suzuki CV carbs work okay. It entailed a ton of jetting changes and eventually modifying the springs on the slides to allow a quicker opening at WOT. Lots of frustration surrounded the carb issue. It's a major sore spot for all involved so I'm going to leave that issue alone for now. 🤪

I can certainly chime in Frank.

[MRieck]

  If there was a converter with a steel turbine, the fins could be laid down and re-brazed. But alas, they're cast aluminum so all that can be done it cut them open and change the gap between the turbines. If a real transmission guy thought there were more than one or two of us interested I'm sure a lot more could be done.

Trying to get that stall to 5,000 RPM or so is a real trick.

[Ben D]

the guy i bought my dragbike off of (david W) said he used to race a hondamatic on the strip and won against a few kz's. he said it terrified him because if the motor locked up youre screwed

[Don R]

 Apparently, Neil Chance converters has rebuilt a couple 750A converters, and a high stall 750A converter may  lose around 20% slip to the rear wheels near the finish line.  They also may have also milled out and then welded in different fin angles to change the stall speed.
 My 9" dragster converter loses 4% behind a 960hp big block at the 1/4 mile, it's a lot more (18% I think) at the 1/8th mile.
 I've been scrolling through J Weeks' posts about 750A's. 

[Tracksnblades1]

  The pot don't stink if you don't stir it. lol.

Stinky Sam here Don, lol.

It's something you'll never find out mate. No one has ever taken a CB750A to the limit in terms of trying to make it the quickest.
In 1980, a CB750K blown nitro bike was the first bike to run in the 7s in the UK, how many people do you know that have supercharged an automatic and run it on nitro ?
Over to you you $hit stirrer. lol.

Sam.

I had to search since a local guy not far from me had a fast CB750 for many years ago. Same guy, Stefan Reisten.

I bought a set of strong rods said to be from his engine on a part meet early or mid 80's.
Lost when moved to my house 2004.
Also found this older post here.
http://forums.sohc4.net/index.php?topic=115272.0

He used a bigger Yamaha engine after the CB750.

Maybe he used same tuning shop as I did and still do. I have to ask the mechanic/tune still working (I have had ideas to gas port  my 71.25mm pistons for my billet block since the tuner mentioned it. Holes from the sides).

That shop's  (Motospeed) owner was a drag racer too, Pro Bike.

About the commercial on bike. "Rasten" was a popular burger, hot dog restaurant in the 70-80's.
Västerås is the name of my town where I live.
Stefan Reisten lived in a small village north of Västerås in the 80's.  Maybe still do.
Same village I have visited a Harley tuner, former HD drag racer for dynos the last 3 years.

We other bikers in Västerås were very proud of those to dragracers early 80's. ;
Edit: How to pronounce Västerås. Wovels ä, å.
- ä as in west
- å as the beginning of Auburn.
We have an wovel ö too. As jerk.

PeWe:

What’s your guy saying percentage wise on the laterally gas ported NA pistons..?
I know it was in the teens or better on surpercharged and gssaed engines..

[PeWe]

  The pot don't stink if you don't stir it. lol.

Stinky Sam here Don, lol.

It's something you'll never find out mate. No one has ever taken a CB750A to the limit in terms of trying to make it the quickest.
In 1980, a CB750K blown nitro bike was the first bike to run in the 7s in the UK, how many people do you know that have supercharged an automatic and run it on nitro ?
Over to you you $hit stirrer. lol.

Sam.

I had to search since a local guy not far from me had a fast CB750 for many years ago. Same guy, Stefan Reisten.

I bought a set of strong rods said to be from his engine on a part meet early or mid 80's.
Lost when moved to my house 2004.
Also found this older post here.
http://forums.sohc4.net/index.php?topic=115272.0

He used a bigger Yamaha engine after the CB750.

Maybe he used same tuning shop as I did and still do. I have to ask the mechanic/tune still working (I have had ideas to gas port  my 71.25mm pistons for my billet block since the tuner mentioned it. Holes from the sides).

That shop's  (Motospeed) owner was a drag racer too, Pro Bike.

About the commercial on bike. "Rasten" was a popular burger, hot dog restaurant in the 70-80's.
Västerås is the name of my town where I live.
Stefan Reisten lived in a small village north of Västerås in the 80's.  Maybe still do.
Same village I have visited a Harley tuner, former HD drag racer for dynos the last 3 years.

We other bikers in Västerås were very proud of those to dragracers early 80's. ;
Edit: How to pronounce Västerås. Wovels ä, å.
- ä as in west
- å as the beginning of Auburn.
We have an wovel ö too. As jerk.

PeWe:

What’s your guy saying percentage wise on the laterally gas ported NA pistons..?
I know it was in the teens or better on surpercharged and gssaed engines..

Not that much details except for more power on dyno he has seen.  I do not remember the details.
It must have been engines for racing.
I'll ask him about details.

[MRieck]

I don't think anybody mentioned this but one of the big limiting factors with a high HP auto engine is the primary chain.....it has very little width and no tensioner.

[Don R]

 It's funny, CycleX has a 750A stroker crank listed because some folks like the hy-vo chain and think it's stronger. I think they use gl1000 parts to get it hooked to the clutch. Or a guy could run a 69mm Automatic stroker. I bet that would flash that old beer can converter higher than stock.

[PeWe]

PeWe:

What’s your guy saying percentage wise on the laterally gas ported NA pistons..?
I know it was in the teens or better on surpercharged and gssaed engines..

Not that much details except for more power on dyno he has seen.  I do not remember the details.
It must have been engines for racing.
I'll ask him about details.

The pistons and billet block are in the shop for gas porting and refresh of bores grinding off residues.
Got it for free so I had to do it He had a batch of other pistons to do so easy to add mine.

It will improve much if top rings do not keep up the pressure with much blow-by.
More torque that give more hp.

I have seen blow-by when revving it. I added extra ventilation in valve cover to make it easier for engine and less oil weeps, mostly around oil filter cover.

Later got oil weeping under cylinder wich I have finally got really dry by adding a thin film og high temp silicone on the thin RCS gasket where it seals to block outer area. Like oil dirty fingers spreading it.

The 970cc with the thicker XC rings in now has not gas ported pistons.