Honda Twins banner

1 - 17 of 17 Posts

·
Registered
Joined
·
18 Posts
Discussion Starter · #1 ·
A thought- has anyone tried an aftermarket upgrade to the CB450 head light? does the charging system make enough power to run them full time?
 

Attachments

·
Registered
Joined
·
2,561 Posts
How much power do they draw? The CB450's charging system barely makes enough power to operate the 35W high beam above 3000rpm; below that, and it will start to discharge. The low beam is 25W, and will make the charging system just about break even when just above idle.
 

·
Registered
Joined
·
3,537 Posts
How much power do they draw? The CB450's charging system barely makes enough power to operate the 35W high beam above 3000rpm; below that, and it will start to discharge. The low beam is 25W, and will make the charging system just about break even when just above idle.
This is true for the K0 to K4. In 1972 Hm upgraded the rectifier from a seliumn bridge to one that used silicon based diodes. Silicon diodes are more efficenct. From the K5 and on the bike's came with a 35/50w headlight. I'm running a 45/45w H4 in my K5. I don't ride this bike at night.
 

·
Registered
Joined
·
2,561 Posts
They must have rewound the stator as well - I have a series-pass regulator, and it charges about the same as the selenium; perhaps a bit better, but not enough to run a 50W lamp, even with LEDs everywhere else. I installed a 30W LED headlamp, which is so much brighter than the filament that I can ride at night - I usually don't, though.

Interesting; I just checked my parts book, and it shows the same rectifier in the K5 as the K3 and K4. Maybe it was updated after my data was released. It does show a different part number for the K5 stator, though.
 

·
Registered
Joined
·
18 Posts
Discussion Starter · #5 ·
They must have rewound the stator as well - I have a series-pass regulator, and it charges about the same as the selenium; perhaps a bit better, but not enough to run a 50W lamp, even with LEDs everywhere else. I installed a 30W LED headlamp, which is so much brighter than the filament that I can ride at night - I usually don't, though.

Interesting; I just checked my parts book, and it shows the same rectifier in the K5 as the K3 and K4. Maybe it was updated after my data was released. It does show a different part number for the K5 stator, though.
Cool! So if I focus on the stator, rotor, and rectifier of a K5 to K7 I should be able to run a 35W projector beam with no issues :ugeek:
 

·
Registered
Joined
·
2,561 Posts
Cool! So if I focus on the stator, rotor, and rectifier of a K5 to K7 I should be able to run a 35W projector beam with no issues :ugeek:
Seems like it. It still may not keep up if you let it idle a long time, but if you install a Voltage monitor, you can avoid that by revving a bit if it drops off.
 

·
Registered
Joined
·
3,537 Posts
Cool! So if I focus on the stator, rotor, and rectifier of a K5 to K7 I should be able to run a 35W projector beam with no issues :ugeek:
My understanding is the stator is the same for all 5sp models. The rectifier changed on the K5 (see www.cmsnl.com CB450K5 USA). All of the large headlight CB450 were equipped with 35/50w healights from the factory (see cmsnl.com CB450K5 and the FSM wiring diagram for K7). The Silcon rectifier was more efficent than the older selinum, or less current loss. My bike is fine with th 45/45w headlight. I have LED tail light and LED dash lights. This give me about 12w back over stock lights. Also the bike has a new harness with all 12GA wire. I want to try a 55/60w H4 next summer to see what happens. The bike does have a voltage meter i can monitor while riding.
 

·
Registered
Joined
·
2,561 Posts
Interesting - my parts list shows only the rotor and stator changed with the CB450K5, and not the rectifier. The K3/K4 rotor is 31101-292-003, while the K5 rotor is 31101-346-670, and the K3/K4 stator is 31102-292-013 and K5 stator is 31102-346-670. These are the part number differences shown at your linked site, too. The rectifier is shown as the same part number on that site (31700-292-008), but listed as superseded by part number 31700-455-671 for all. So, the big change was rotor and stator, not the rectifier, although I'm sure the latter helps.

Wow! I just looked at the price for the generator set - $1325!!!
 

·
Registered
Joined
·
3,537 Posts
Interesting - my parts list shows only the rotor and stator changed with the CB450K5, and not the rectifier. The K3/K4 rotor is 31101-292-003, while the K5 rotor is 31101-346-670, and the K3/K4 stator is 31102-292-013 and K5 stator is 31102-346-670. These are the part number differences shown at your linked site, too. The rectifier is shown as the same part number on that site (31700-292-008), but listed as superseded by part number 31700-455-671 for all. So, the big change was rotor and stator, not the rectifier, although I'm sure the latter helps.

Wow! I just looked at the price for the generator set - $1325!!!
Wintrsol,
It is my understanding all of the 5sp stators were equivelent in terms of electrical output. This is an assumption based on studing the Honda Factory Shop Manual and reading this forum. I agree Honda used different part numbers. Honda changed from Selenium diode rectifiers to Silicon diode rectifiers in the 1972 year. I think this applies to the 350 series too. All diodes Selenium and Silicon exhibit a voltage drop. A Selenium rectifier will have about a 1v drop and a modern Silicon rectifier will have about a .1v drop. At 13v (CB450 operating range for the electrical system) that is about a 12w difference in output.
these are the FSM references:
FSM P107 AC Charging System.jpg
This is page 107 from the FSM. It notes the Selenium rectifier as part of the original K0 specification. The changes are listed:


FSM P170 Silcon Rectifier.jpg
This is page 170 from the FSM where the K5 Silicon recitfier is replaced with the newer K6 style. This rectifier was used through the K7.

FSM CB450K5 Wire Diagram.jpg
The FSM wiring diagram for the K7 shows the 35/50W headlight. The same headlight was used in the K5 through the K7. Interesting to note the CL still used the 25/35w headlight.

So my theory is the original silicon rectifier got the charging system to a 50w headlight, the use of LED tail and dask lights should give back another 12w. That should get you to a 55/60w Halogen headlight. This should apply to all 5sp models. We will see.
 

·
Registered
Joined
·
2,561 Posts
Wintrsol,
It is my understanding all of the 5sp stators were equivelent in terms of electrical output. This is an assumption based on studing the Honda Factory Shop Manual and reading this forum. I agree Honda used different part numbers. Honda changed from Selenium diode rectifiers to Silicon diode rectifiers in the 1972 year. I think this applies to the 350 series too. All diodes Selenium and Silicon exhibit a voltage drop. A Selenium rectifier will have about a 1v drop and a modern Silicon rectifier will have about a .1v drop. At 13v (CB450 operating range for the electrical system) that is about a 12w difference in output.
A good quality silicon rectifier will exhibit ~0.6V drop with any significant amount of current; even a Schottky diode starts in the 0.4V range, increasing with increasing current. Schottky diodes have a lot of reverse leakage, though, so aren't a good choice. So, your calculation of available power increase is a little off.
The FSM indicates in the first drawing that the K0 full-wave current at idle rpm of ~3A at roughly 12.6V, that's 39W total. It also shows that charging current starts at 1500 rpm, so, with a 25W headlamp, the rest of the system draws more than 14W. The chart on the facing page implies that the coils average about 14W, since the other lamps total 14W, and power available at 1500 rpm is about 14W higher than at idle. Increasing the Voltage by ~0.4V would increase the available power by around 1.2W, or to just over 40W. I don't know the details of the stator and rotor, but that extra 15W has to come from somewhere - the diodes, alone, can't provide it. Even if the diode drop is only 0.1V, as you assert, that is only an increase of about 3W at idle. Adding 15W would require a increase of more than 1A at idle; which may be true of the K3 stator/rotor combo, but finding this data seems impossible. If the K3 and up is capable of >64W at idle, it would have to output ~4.8A (64W/13.4V), which is a BIG increase over the K0. I suppose that's possible. but my K3 will very slowly discharge the battery at 1000 rpm with the 30W LED lamp, and LEDs in the gauges and tail lamp, using a good quality series-pass regulator with silicon electronics inside. My total lighting power is about 35W, so adding the ~14W of the coils makes ~49W load, which appears to be just a bit more than the generating system can provide at idle.
 

·
Premium Member
Joined
·
1,406 Posts
I still use the original set-up on my K0, never trickle charge the battery. I usually kickstart the bike instead of using the electric starter, that alone saves a lot of energy.
I did replace the neutral light with a LED, and the speedo backlights too. To me, the main issue is that people don't rev the bike enough, staying around 2000 to 3000 rpm won't do. Another issue I see is the resistance of the connectors (old and corroded). Cleaning them, and make a tight fit will usually make the electrical system much better.
 
  • Like
Reactions: Lefty

·
Registered
Joined
·
2,837 Posts
I'll throw my bummer opinion in cause I'm bored. Why would you want to change the charming old lights out from these character filled old bikes? Change to a modern Reg/rect and keep them revs up:)
 

·
Premium Member
Joined
·
1,406 Posts
Why would you want to change the charming old lights out from these character filled old bikes?
For the headlight I understand, using a new reflector alone does make it a lot better, keeping the charming filament bulb.
For riding at night on a highway however......
 

·
Registered
Joined
·
2,837 Posts
For the headlight I understand, using a new reflector alone does make it a lot better, keeping the charming filament bulb.
For riding at night on a highway however......

Yes! Or make a new one like this guy.

Sorry, I won't hijack this anymore:)
 

·
Registered
Joined
·
2,561 Posts
FWIW, the K4 owner's manual says the charging system produces 110W at 3000rpm, which agrees with the data in the service manual for the K0, so the stator and rotor part number differences must be for other reasons than power output, unless the number for the K5 is different.
 
1 - 17 of 17 Posts
Top