Author Topic: Specific engine mounting difference... 750A vs 750K  (Read 618 times)

0 Members and 1 Guest are viewing this topic.

Offline fxef79

  • Enthusiast
  • **
  • Posts: 170
Specific engine mounting difference... 750A vs 750K
« on: April 18, 2020, 02:13:48 pm »
I have a custom frame trike that has a 750K engine in it.  I suspect, based on what I see has been done to the engine mounting tabs by someone in the past, and due to some notes on some service workorders I got in a folder from the previous owner, this frame used to have a 750A engine in it.  What I'm guessing is that the engine mounting points for a 750K and 750A are all the exact same, EXCEPT for one: the upper right rear mount... I don't have access to any actual 750A frames or engines (or complete bikes) to confirm this.  But the upper right rear mounting tab is cut off and thus my 750K engine isn't bolted to anything there.
 
Does anyone have access to BOTH 750K and 750A frames and engines that could confirm (maybe with pics?) the differences between the upper rear right side mounting brackets?

Offline Don R

  • My Sandcast is a
  • Really Old Timer ...
  • *******
  • Posts: 13,369
  • Saver of unloved motorcycles.
Re: Specific engine mounting difference... 750A vs 750K
« Reply #1 on: May 10, 2020, 09:38:01 pm »
 My stuff is buried in the shop but the upper right rear tab is a bolt on affair that bolts both through the engine case and the frame.  I'll see what I can find tomorrow for pictures.
No matter how many times you paint over a shadow, it's still there.

Offline 754

  • Really Old Timer ...
  • *******
  • Posts: 28,507
Re: Specific engine mounting difference... 750A vs 750K
« Reply #2 on: May 10, 2020, 09:58:49 pm »
There is 2 types, most are flat and go behind the frame. Late ones have a few bends and go to outside of frame. .
Maker of the WELDLESS 750 Frame Kit
dodogas99@gmail.com
Kelowna B.C.       Canada

My next bike will be a ..ANFOB.....

It's All part of the ADVENTURE...

73 836cc.. Green, had it for 3 decades!!
Lost quite a few CB 750's along the way

Offline Don R

  • My Sandcast is a
  • Really Old Timer ...
  • *******
  • Posts: 13,369
  • Saver of unloved motorcycles.
Re: Specific engine mounting difference... 750A vs 750K
« Reply #3 on: May 11, 2020, 10:05:07 pm »
 Frank reminded me two of those plates separated by a tube welded between them and a long (F?) engine mount bolt equals a performance mod. 
No matter how many times you paint over a shadow, it's still there.

Offline Sam Green Racing

  • Moderator
  • Really Old Timer ...
  • *****
  • Posts: 15,909
  • I REALLY? hate black rims.
Re: Specific engine mounting difference... 750A vs 750K
« Reply #4 on: May 12, 2020, 10:18:23 am »
Like Frank and Don said, which ever rear mount you use, you should be OK with either.
If the trike chassis was built specifically for the automatic motor, you might run into another problem depending on what year the K motor is.
Rear drive chain alignment is the same for Automatic, late F and late K8 models. Earlier K models have a different chain alignment.
Good luck.

Sam.
C95 sprint bike.
CB95 hybrid race bike
CB95 race bike
CB92
RS 175. sprint/land speed bike
JMR Racing CB750A street ET drag bike

Offline ebrown0104

  • Full Member
  • *
  • Posts: 18
Re: Specific engine mounting difference... 750A vs 750K
« Reply #5 on: May 17, 2020, 09:57:58 pm »
So basically if I'd get a 77 or 78 K model engine, add a Sump Thing oil pan to it, and a clutch cable (and a tach, though not 100% needed) it should be a bolt in affair to my 78 A?

Offline Sam Green Racing

  • Moderator
  • Really Old Timer ...
  • *****
  • Posts: 15,909
  • I REALLY? hate black rims.
Re: Specific engine mounting difference... 750A vs 750K
« Reply #6 on: May 18, 2020, 02:59:41 pm »
So basically if I'd get a 77 or 78 K model engine, add a Sump Thing oil pan to it, and a clutch cable (and a tach, though not 100% needed) it should be a bolt in affair to my 78 A?

Yes with the 78K but I'm not sure about the 77K.
All motors will go in any frame.
All swingarms will mate up to all frames  but with earlier K motors, the chain alignment is out by 5/8ths of an inch.
I found this out when I tried to mate up an aftermarket swingarm made for the early K. I fitted it to my 76 Automatic and chain alignment was out by 5/8th of an inch.
Don't take my word for it, ask around and please post your findings back here, I'll do the same also.

Sam.
C95 sprint bike.
CB95 hybrid race bike
CB95 race bike
CB92
RS 175. sprint/land speed bike
JMR Racing CB750A street ET drag bike

Offline Medyo Bastos

  • Expert
  • ****
  • Posts: 1,261
  • Gusto mo titi ko?
    • project
Re: Specific engine mounting difference... 750A vs 750K
« Reply #7 on: May 18, 2020, 03:27:56 pm »
The bottom is different too, needing spacers on the bolt. An a engine fits a k frame, but you have to roll the engine in because the sump is so deep. The stock a frame has curved tubes over the cam cover to allow easier removal and reinstallation. The mounting clearance needs massaging on a k frame on the lower right to accept the torque converter. Not a big deal.


Sent from my iPhone using Tapatalk

Offline Sam Green Racing

  • Moderator
  • Really Old Timer ...
  • *****
  • Posts: 15,909
  • I REALLY? hate black rims.
Re: Specific engine mounting difference... 750A vs 750K
« Reply #8 on: May 18, 2020, 04:33:28 pm »
The bottom is different too, needing spacers on the bolt. An a engine fits a k frame, but you have to roll the engine in because the sump is so deep. The stock a frame has curved tubes over the cam cover to allow easier removal and reinstallation. The mounting clearance needs massaging on a k frame on the lower right to accept the torque converter. Not a big deal.


Sent from my iPhone using Tapatalk

Hi Medyo, he's doing it the other way round mate. The K motor will fall into an Automatic frame.
Even if the Sumpthing is deeper than the auto sump, he can always fit it after installation.

Sam.
C95 sprint bike.
CB95 hybrid race bike
CB95 race bike
CB92
RS 175. sprint/land speed bike
JMR Racing CB750A street ET drag bike

Offline Medyo Bastos

  • Expert
  • ****
  • Posts: 1,261
  • Gusto mo titi ko?
    • project
Re: Specific engine mounting difference... 750A vs 750K
« Reply #9 on: May 18, 2020, 04:36:51 pm »
Sorry I didn’t read through all the posts. It’ll be easier then because of the curved top tubes. He can leave the sumpthing on as well. Easy, peasy


Sent from my iPhone using Tapatalk

Offline Sam Green Racing

  • Moderator
  • Really Old Timer ...
  • *****
  • Posts: 15,909
  • I REALLY? hate black rims.
Re: Specific engine mounting difference... 750A vs 750K
« Reply #10 on: May 18, 2020, 06:08:14 pm »
Cool my friend, I hope you are well and stay safe.
C95 sprint bike.
CB95 hybrid race bike
CB95 race bike
CB92
RS 175. sprint/land speed bike
JMR Racing CB750A street ET drag bike

Offline fxef79

  • Enthusiast
  • **
  • Posts: 170
Re: Specific engine mounting difference... 750A vs 750K
« Reply #11 on: May 24, 2020, 11:46:13 am »
Like Frank and Don said, which ever rear mount you use, you should be OK with either.
If the trike chassis was built specifically for the automatic motor, you might run into another problem depending on what year the K motor is.
Rear drive chain alignment is the same for Automatic, late F and late K8 models. Earlier K models have a different chain alignment.
Good luck.

Sam.

I believe the frame was built specifically for the standard motor, not automatic.  But I believe someone mounted an automatic motor in it in the past - and to do that they cut off that upper right rear tab.  So there's no tab there at all to bolt the motor to, unlike on the other side.

Pics below of both sides.

Yes, the left side rear of the case has some bits broken off.  NOT a pristine engine, by any means.


Offline Don R

  • My Sandcast is a
  • Really Old Timer ...
  • *******
  • Posts: 13,369
  • Saver of unloved motorcycles.
Re: Specific engine mounting difference... 750A vs 750K
« Reply #12 on: May 26, 2020, 03:13:04 pm »
 I did move  couple bikes to get a pic but the mount isn't there. fooey.
No matter how many times you paint over a shadow, it's still there.

Offline Medyo Bastos

  • Expert
  • ****
  • Posts: 1,261
  • Gusto mo titi ko?
    • project
Re: Specific engine mounting difference... 750A vs 750K
« Reply #13 on: May 26, 2020, 03:32:40 pm »
What mount Don?


Sent from my iPhone using Tapatalk

Offline 754

  • Really Old Timer ...
  • *******
  • Posts: 28,507
Re: Specific engine mounting difference... 750A vs 750K
« Reply #14 on: May 26, 2020, 03:50:38 pm »
Ok so sprocket offset, far as I know 10mm.
 And the frame was changed up top, not for top end removal, but for install with the A sump on...is what I had read.
 What I don't know is the Height of the A pan, vs the Sump thing.
 One thing I wonder about , is the A 2 into 1 pipes, Medyo may know will they fit an Amen frame ? The tubing is further from the engine than a K model 750,and they would give excellent ground clearance.. and I have 1.5 sets. .  BTW I have a rolling Amen with engine,  that I can try it on , just have not pulled the pipes yet.
« Last Edit: May 26, 2020, 10:26:55 pm by 754 »
Maker of the WELDLESS 750 Frame Kit
dodogas99@gmail.com
Kelowna B.C.       Canada

My next bike will be a ..ANFOB.....

It's All part of the ADVENTURE...

73 836cc.. Green, had it for 3 decades!!
Lost quite a few CB 750's along the way

Offline Medyo Bastos

  • Expert
  • ****
  • Posts: 1,261
  • Gusto mo titi ko?
    • project
Re: Specific engine mounting difference... 750A vs 750K
« Reply #15 on: May 26, 2020, 03:54:08 pm »
Who is metros? What a exhaust do you mean? Do you have pics for reference?


Sent from my iPhone using Tapatalk

Offline 754

  • Really Old Timer ...
  • *******
  • Posts: 28,507
Re: Specific engine mounting difference... 750A vs 750K
« Reply #16 on: May 26, 2020, 10:30:26 pm »
I meant Medyo, freaking spellhelpernot or auto prompt, have to check every freaking sentence.
 Some years of Autos had welded 2 into one pipes, I have some but not yet tried them .
 I can take a pic of my pipes soon, here is pic , but cant see much.
« Last Edit: May 26, 2020, 10:47:24 pm by 754 »
Maker of the WELDLESS 750 Frame Kit
dodogas99@gmail.com
Kelowna B.C.       Canada

My next bike will be a ..ANFOB.....

It's All part of the ADVENTURE...

73 836cc.. Green, had it for 3 decades!!
Lost quite a few CB 750's along the way

Offline Medyo Bastos

  • Expert
  • ****
  • Posts: 1,261
  • Gusto mo titi ko?
    • project
Re: Specific engine mounting difference... 750A vs 750K
« Reply #17 on: May 27, 2020, 05:22:06 am »
No help here. I’ve never run that exhaust before.


Sent from my iPhone using Tapatalk

Offline Don R

  • My Sandcast is a
  • Really Old Timer ...
  • *******
  • Posts: 13,369
  • Saver of unloved motorcycles.
Re: Specific engine mounting difference... 750A vs 750K
« Reply #18 on: May 28, 2020, 07:09:22 pm »
What mount Don?


Sent from my iPhone using Tapatalk
I offered to get a pic of my A upper right mount but there was a lift and a couple bikes in the way. When I got it exposed the mount was removed already. So, no help from me.
No matter how many times you paint over a shadow, it's still there.

Offline Medyo Bastos

  • Expert
  • ****
  • Posts: 1,261
  • Gusto mo titi ko?
    • project
Re: Specific engine mounting difference... 750A vs 750K
« Reply #19 on: May 28, 2020, 08:26:12 pm »
See if this helps





Sent from my iPhone using Tapatalk