Author Topic: CB750R magneto  (Read 4802 times)

0 Members and 2 Guests are viewing this topic.

Offline Jadahonda

  • Full Member
  • *
  • Posts: 69
CB750R magneto
« on: December 22, 2015, 12:05:46 PM »
Is there someone who have one of this for sale?
Jan
1958 Honda C70 Dream
1959 Honda C92 Benly
1960 Honda CS92 Ongoing Project
1960 Honda CB92 Benly
1960 Honda CB92 Racer
1961 Honda CB72 Racer
1962 Honda CS92
1963 Honda CB77 Ongoing Project
1967 Honda CB450 Black Bomber
1968 Honda Z50A
1969 Honda CB750 K0
1969 Honda CB750 Sandcast
1969 Honda CR750-Ongoing Project
1970 Honda CB750 Police
1970 Honda CB100
1970 Honda CL100
1970 Honda SL100
1971 Honda CB500
1975 Honda GL1000
1975 Honda CB400F Supersport
1979 Honda CBX 1000, serial number 52
1981 Honda CBX 1000 ProLink
1989 Honda VFR400R (NC30)

Offline Bill/BentON Racing

  • Really Old Timer ...
  • *******
  • Posts: 6,725
  • Ex Honda Service Manager, Cert. Honda Tech - Racer
    • BentON Racing
Re: CB750R magneto
« Reply #1 on: December 22, 2015, 04:45:36 PM »
I have the stator! You want a pic? Bill
BentON Racing Website
OEM Parts | Service | Custom Builds
BentON Racing Facebook
Over 35 years of experience working on vintage motorcycles, with a speciality in Honda SOHC/4 with a focus on the CB750 and other models as well from 1966 - 1985.
______________________________________
1993 HRC RS125 | 1984 NS400R | 1974 Honda CB750/836cc (Calendar Girl) | 1972 CB 500/550 Yoshi Kitted 590cc | 1965 Honda CB450 Black Bomber | 1972 Suzuki T350 | 1973 88cc | Z50/Falcons Pit Bike | 1967 CA100| 1974 CB350 (400F motor)...and more.
______________________________________
See our latest build 'Captain Marvel' CLICK HERE

Offline kmb69

  • Master
  • *****
  • Posts: 2,041
Re: CB750R magneto
« Reply #2 on: December 22, 2015, 05:45:52 PM »
Those 4 pole rotors are hard to come by. Been looking for one for a few years now.

Offline 754

  • Really Old Timer ...
  • *******
  • Posts: 29,058
Re: CB750R magneto
« Reply #3 on: December 22, 2015, 06:47:30 PM »
Is the centre part from CB 350 ,. Or .175/185.  ?
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 kmb69

  • Master
  • *****
  • Posts: 2,041
Re: CB750R magneto
« Reply #4 on: December 22, 2015, 07:05:29 PM »
It is a CR750 magneto and has a 4 pole rotor.
The bikes you mentioned have 6 pole rotors.

Offline bwaller

  • Really Old Timer ...
  • *******
  • Posts: 7,484
Re: CB750R magneto
« Reply #5 on: December 22, 2015, 08:05:30 PM »
I always heard they modified a CB77 rotor.

Offline kmb69

  • Master
  • *****
  • Posts: 2,041
Re: CB750R magneto
« Reply #6 on: December 22, 2015, 09:12:43 PM »
Pretty sure the CB77 rotors are 6 pole rotors.

Offline Bill/BentON Racing

  • Really Old Timer ...
  • *******
  • Posts: 6,725
  • Ex Honda Service Manager, Cert. Honda Tech - Racer
    • BentON Racing
Re: CB750R magneto
« Reply #7 on: December 22, 2015, 09:54:12 PM »
Bet you going to check again! Lol, Bill  ;D
BentON Racing Website
OEM Parts | Service | Custom Builds
BentON Racing Facebook
Over 35 years of experience working on vintage motorcycles, with a speciality in Honda SOHC/4 with a focus on the CB750 and other models as well from 1966 - 1985.
______________________________________
1993 HRC RS125 | 1984 NS400R | 1974 Honda CB750/836cc (Calendar Girl) | 1972 CB 500/550 Yoshi Kitted 590cc | 1965 Honda CB450 Black Bomber | 1972 Suzuki T350 | 1973 88cc | Z50/Falcons Pit Bike | 1967 CA100| 1974 CB350 (400F motor)...and more.
______________________________________
See our latest build 'Captain Marvel' CLICK HERE

Offline Jadahonda

  • Full Member
  • *
  • Posts: 69
Re: CB750R magneto
« Reply #8 on: December 23, 2015, 12:55:52 AM »
I know that there was made 2 magnetos for the 750 who fitted the small cover. one with -970, and an improved 971. There was also one who fit the big cover who was used in enduro racing.

I think they are very similar who was for CYB72, CR93, and more...

Yoshimura also made one for CR750, a kit was sold here earlier.
1958 Honda C70 Dream
1959 Honda C92 Benly
1960 Honda CS92 Ongoing Project
1960 Honda CB92 Benly
1960 Honda CB92 Racer
1961 Honda CB72 Racer
1962 Honda CS92
1963 Honda CB77 Ongoing Project
1967 Honda CB450 Black Bomber
1968 Honda Z50A
1969 Honda CB750 K0
1969 Honda CB750 Sandcast
1969 Honda CR750-Ongoing Project
1970 Honda CB750 Police
1970 Honda CB100
1970 Honda CL100
1970 Honda SL100
1971 Honda CB500
1975 Honda GL1000
1975 Honda CB400F Supersport
1979 Honda CBX 1000, serial number 52
1981 Honda CBX 1000 ProLink
1989 Honda VFR400R (NC30)

Offline Jadahonda

  • Full Member
  • *
  • Posts: 69
Re: CB750R magneto
« Reply #9 on: December 23, 2015, 01:08:17 AM »
Do you want to sell the stator?
My mail is: jan@tveten.biz
1958 Honda C70 Dream
1959 Honda C92 Benly
1960 Honda CS92 Ongoing Project
1960 Honda CB92 Benly
1960 Honda CB92 Racer
1961 Honda CB72 Racer
1962 Honda CS92
1963 Honda CB77 Ongoing Project
1967 Honda CB450 Black Bomber
1968 Honda Z50A
1969 Honda CB750 K0
1969 Honda CB750 Sandcast
1969 Honda CR750-Ongoing Project
1970 Honda CB750 Police
1970 Honda CB100
1970 Honda CL100
1970 Honda SL100
1971 Honda CB500
1975 Honda GL1000
1975 Honda CB400F Supersport
1979 Honda CBX 1000, serial number 52
1981 Honda CBX 1000 ProLink
1989 Honda VFR400R (NC30)

Offline Bill/BentON Racing

  • Really Old Timer ...
  • *******
  • Posts: 6,725
  • Ex Honda Service Manager, Cert. Honda Tech - Racer
    • BentON Racing
Re: CB750R magneto
« Reply #10 on: December 23, 2015, 03:50:56 AM »
Yes, I will. I'll send you some pics, Bill
BentON Racing Website
OEM Parts | Service | Custom Builds
BentON Racing Facebook
Over 35 years of experience working on vintage motorcycles, with a speciality in Honda SOHC/4 with a focus on the CB750 and other models as well from 1966 - 1985.
______________________________________
1993 HRC RS125 | 1984 NS400R | 1974 Honda CB750/836cc (Calendar Girl) | 1972 CB 500/550 Yoshi Kitted 590cc | 1965 Honda CB450 Black Bomber | 1972 Suzuki T350 | 1973 88cc | Z50/Falcons Pit Bike | 1967 CA100| 1974 CB350 (400F motor)...and more.
______________________________________
See our latest build 'Captain Marvel' CLICK HERE

Offline Jadahonda

  • Full Member
  • *
  • Posts: 69
Re: CB750R magneto
« Reply #11 on: December 23, 2015, 08:24:45 AM »
Send them to: jan@tveten.biz, and a price you ask for it...

Jan
1958 Honda C70 Dream
1959 Honda C92 Benly
1960 Honda CS92 Ongoing Project
1960 Honda CB92 Benly
1960 Honda CB92 Racer
1961 Honda CB72 Racer
1962 Honda CS92
1963 Honda CB77 Ongoing Project
1967 Honda CB450 Black Bomber
1968 Honda Z50A
1969 Honda CB750 K0
1969 Honda CB750 Sandcast
1969 Honda CR750-Ongoing Project
1970 Honda CB750 Police
1970 Honda CB100
1970 Honda CL100
1970 Honda SL100
1971 Honda CB500
1975 Honda GL1000
1975 Honda CB400F Supersport
1979 Honda CBX 1000, serial number 52
1981 Honda CBX 1000 ProLink
1989 Honda VFR400R (NC30)

Offline Old Scrambler

  • My CB750K3 has been in 39 States & 5 Provinces
  • Old Timer
  • ******
  • Posts: 3,807
Re: CB750R magneto
« Reply #12 on: December 23, 2015, 06:26:42 PM »
CB72 and other early twin models have 6-pole stators................they look similar to that CR unit and are 12v ...........they may fit but I have no CR cover to match-up. 
Dennis in Wisconsin
'64 Triumph Cub & '74 Honda CB750 Bonneville Salt Flats AMA Record Holder (6)
CB750 Classic Bonneville Racer thread - http://forums.sohc4.net/index.php/topic,135473.0.html
'63 CL72 Project(s)
'66 CL77 Red
'67 Triumph T100C
'73 750K3 Owned since New
'77 750F2 Cafe Project
2020 ROYAL ENFIELD Himalayan

Offline 754

  • Really Old Timer ...
  • *******
  • Posts: 29,058
Re: CB750R magneto
« Reply #13 on: December 23, 2015, 06:30:33 PM »
On a 6 pole, are two extra for lighting...  I seem to remember..and your light switch kicks in the xtra windings ?
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 kmb69

  • Master
  • *****
  • Posts: 2,041
Re: CB750R magneto
« Reply #14 on: December 23, 2015, 08:02:12 PM »
On a 6 pole, are two extra for lighting...  I seem to remember..and your light switch kicks in the xtra windings ?
Totally depends on system design. They are normally designed as related to power requirements. A 6 pole system can be single, 2 wires, or three phase, 3 wires. Could be up to 3 single phase, 6 wires, or 2 three phase, 6 wires, I guess. Depends on how it is wired. Not sure about the extra lighting thing because most of these permanent magnet alternators only used a rectifier to convert AC to DC and the battery was sized to be the "buffer" instead of having a regulator. Many of the English bikes, BSA, Triumph, and Norton, used a Zener Diode on the end of the circuit for voltage regulation in both single and three phase systems as I recall. Many of the smaller Hondas used two separate stator coils, one for ignition and the other for lighting. Studying some of those wiring diagrams would probably shed more light on the matter.

The CR magneto was designed to run sans a battery. The leads are connected directly to the coils usually via a kill switch. My electrical prowess is somewhat shabby and I really don't know how it worked without a rectifier. It was basically wired as 2 single phase systems, 4 wires. I ran one many moons ago and it was somewhat critical to have the rotor and stator "aligned" to properly "charge" the coils for the desired spark timing (no keyway on the crank). Honda provided no instructions that I am aware of. The spark "advancer", or points cam, was fixed (no advance, no retard). It was designed to operate at 35 degrees BTDC if my memory serves correctly.
« Last Edit: December 23, 2015, 08:04:26 PM by kmb69 »

Online Don R

  • My Sandcast is a
  • Really Old Timer ...
  • *******
  • Posts: 19,830
  • Saver of unloved motorcycles.
Re: CB750R magneto
« Reply #15 on: December 23, 2015, 10:21:10 PM »
It needs to be 4 pole for timing?
No matter how many times you paint over a shadow, it's still there.
 CEO at the no kill motorcycle shop.
 You don't need a weatherman to know which way the wind blows.

Offline kmb69

  • Master
  • *****
  • Posts: 2,041
Re: CB750R magneto
« Reply #16 on: December 24, 2015, 07:02:57 AM »
Don, I think so. It was necessary to have a pulse going to the coils at the right time. But like I said, I am not an electrical wizard and frequently have trouble getting my head around how sparks fly. I know there are some on this forum that could provide a proper explanation of how this works. Somebody? Anybody?
« Last Edit: December 24, 2015, 07:06:16 AM by kmb69 »

Offline Greggo

  • Somebody's
  • Old Timer
  • ******
  • Posts: 4,164
  • Helmets Save Lives. Period.
Re: CB750R magneto
« Reply #17 on: December 24, 2015, 11:55:57 AM »
Sold these a year or two ago...Also had the four pole rotor.



Offline 754

  • Really Old Timer ...
  • *******
  • Posts: 29,058
Re: CB750R magneto
« Reply #18 on: December 24, 2015, 03:15:50 PM »
The black cover. Looks like magnesium.

 The part that holes the 4 coils, is it one piece or laminations ?
Anything with lamnations was difficult to make for a few pieces, but with a waterjet, its just cake..
Maybe a few should be made..
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 Greggo

  • Somebody's
  • Old Timer
  • ******
  • Posts: 4,164
  • Helmets Save Lives. Period.
Re: CB750R magneto
« Reply #19 on: December 24, 2015, 03:27:58 PM »
Yes, that one's magnesium.


Offline napoleonb

  • Enthusiast
  • **
  • Posts: 193
Re: CB750R magneto
« Reply #20 on: December 24, 2015, 04:34:27 PM »
This is the best picture I've got of an CR750 rotor and stator.
It appears to be mainly the same in lay-out as the CB77 / C90 / S90 etc. bikes, the latter being the same diameter but with less height.
Apart for the different number of coils and the way they are wound (early S90's were wound the same way) I can spot no significant change other than that the steel insert would probably have been greater on the CR750 item.

Offline scottly

  • Global Moderator
  • Really Old Timer ...
  • *****
  • Posts: 16,267
  • Humboldt, AZ
Re: CB750R magneto
« Reply #21 on: December 24, 2015, 05:02:20 PM »
Don, I think so. It was necessary to have a pulse going to the coils at the right time. But like I said, I am not an electrical wizard and frequently have trouble getting my head around how sparks fly. I know there are some on this forum that could provide a proper explanation of how this works. Somebody? Anybody?
As the magnet in the rotor approaches the stator pole piece, the voltage (and current) generated in the stator coil, as well as in the ignition coil primary begins to rise, peaking when the magnet is centered on the pole piece, and declines as the magnet moves past the pole. Ideally the points should open near the point where the power fed to the coil is the greatest, so the magnet needs to be timed to the stator at that point. Make any sense??
Don't fix it if it ain't broke!
Helmets save brains. Always wear one and ride like everyone is trying to kill you....

Online Don R

  • My Sandcast is a
  • Really Old Timer ...
  • *******
  • Posts: 19,830
  • Saver of unloved motorcycles.
Re: CB750R magneto
« Reply #22 on: December 25, 2015, 09:58:51 PM »
Yes thanks for the explaination. I've learned something.
No matter how many times you paint over a shadow, it's still there.
 CEO at the no kill motorcycle shop.
 You don't need a weatherman to know which way the wind blows.

Offline 754

  • Really Old Timer ...
  • *******
  • Posts: 29,058
Re: CB750R magneto
« Reply #23 on: December 25, 2015, 11:36:17 PM »
Aaaahhhhhhh..so the 6pole would be perfect for a CBX ...!  !
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 Jadahonda

  • Full Member
  • *
  • Posts: 69
Re: CB750R magneto
« Reply #24 on: December 27, 2015, 06:26:58 AM »
Then I have got a stator from Bill.... :)

Is is probably stupid, but is there someone who have a 4-pole rortr for sale also?

Jan
1958 Honda C70 Dream
1959 Honda C92 Benly
1960 Honda CS92 Ongoing Project
1960 Honda CB92 Benly
1960 Honda CB92 Racer
1961 Honda CB72 Racer
1962 Honda CS92
1963 Honda CB77 Ongoing Project
1967 Honda CB450 Black Bomber
1968 Honda Z50A
1969 Honda CB750 K0
1969 Honda CB750 Sandcast
1969 Honda CR750-Ongoing Project
1970 Honda CB750 Police
1970 Honda CB100
1970 Honda CL100
1970 Honda SL100
1971 Honda CB500
1975 Honda GL1000
1975 Honda CB400F Supersport
1979 Honda CBX 1000, serial number 52
1981 Honda CBX 1000 ProLink
1989 Honda VFR400R (NC30)