Author Topic: Hondaman...this question is for you  (Read 7228 times)

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Offline KRONUS0100

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Hondaman...this question is for you
« on: August 10, 2008, 05:08:56 AM »
Curious and confused.  Read your coil analysis.  Interesting.  Also believe that you are the one on here who makes a resistor block for the dyna coils?  My 76 Cb750F has been running a DYNA S ignition for 3 1/2 years now.  I put the Dyna green 3 ohm coils on it a year ago.  I just switched the entire wiring harness and put the coil power feed on a separate 14 gauge wire.  Seems to run better......but do I really need the resistor set?  How do I know I need it?  By the way...I run a AGM battery from Batterystuff.com.
MATT
current bikes:  1976 CB750F, 1981 GS1100E
bikes owned:1981 GL1100I, 1990 GS500E, 1981 GS850, 1977 and 1979 GS750, 1974 CB750, 1975 CB750, and a 1982 GS750E

Offline HondaMan

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Re: Hondaman...this question is for you
« Reply #1 on: August 10, 2008, 08:13:58 PM »
You're in the perfect spot to answer quesitons about the AGM batteries, then! I'll trade questions with you....  ;D

The stock battery voltage on these CB750 bikes is in the range of 12.6v at idle to 13.6v at 3500 RPM, typically. This presumes the battery has been used within the last few days, and a good digital meter is being used to take the readings.

The "break-even" point, i.e., the RPM where the battery discharge stops and alternator charge starts, is around 2000 RPM (sealed beam headlight, lights on). This can be seen on a voltmeter as a sudden rising reading at this RPM, reading taken across the battery. (An easier way: connect an ammeter across the fuse terminals and remove the fuse, run on the meter instead, read current directly.)

Typically, installing extra loads causes this "break-even" point to rise in RPM. A halogen headlight like my H4 (50/55W) makes "break-even" happen at about 2250 RPM, compared to a sealed-beam headlight (extra 250 RPM). Adding 3-ohm Dyna coils forces this "break-even" point to rise further, to approximately 3100 RPM on my bike. This is equivalent to almost 3 extra amps of current added to the system.

This extra RPM isn't a terrible, immediate problem, if you're not forced to idle in traffic a lot. Lots of idling will drag the system voltage down considerably: also, if your riding style is to shift early and putter along, this problem will become worse. If you ride with revs up, passing 4K on every shift, the voltage will be better. Low batteries die early deaths.

Long term, the 3-ohm coils have shown another issue: heating of the splices in the BLACK wire distribution of the Honda wire harness. This causes them to crystallize their solder and become poor connections, sometimes failing in "soft" ways, like hidden voltage drops. Your method of shunting past these with the extra wire is a good one to prevent this problem. On mine, I have added an extra 20 AWG BLACK and 18 AWG ground to the original harness, carrying extra current around those splices and rejoining the harness in the headlight. This accomplishes the same thing, but without the relay and its additional current draw and complexity, which wire novices tend to avoid or not understand very well.

The Resistor Pack is the easiest way I could think of (and used to be Dyna's recommended way) to adapt the 3-ohm coils to these bikes without causing problems. These coils generate  more than 3 times the Honda coils' voltage (if you open the plug gaps to force it up higher), so losing about 15% of it to an inline resistor is not much of an issue, unless you're running nitro or alcohol. In the "old days", at Dyna's direction, the recommended installation was to go to an auto parts store and get the Resistance Wire found in Fords and Chevies (1.1 to 1.8 ohms), coil it up under the battery box, and feed it inline to the coils. Those parts are hard to find today, and made ugly installations, anyway...so I made this version.

Something 'new' has happened at Dyna lately (like in the last 5-8 years) regarding their "installation recommendations" people, I'm not sure what... In years past, my discussions with Dyna engineers (actually, just the one who designed the "S" triggers) yielded the advice that "S" triggers were able to handle 4 amps on a fully-heated (255 degrees) CB750K engine. Since the 3-ohm coils pass (13.6v/3)=4.5 amps, the combination of "S" and 3-ohms were specifically not recommended. The Dyna III was specifically designated to solve this problem, with its separate 6-amp amplifier for the "S" triggers. Today, however, I am hearing that riders are advised that "S" with 3-ohms is an OK combination. Also, however, I know of 3 such systems, installed last winter, that died this year with shorted (i.e., overheated) "S" triggers before summer even arrived. So, it seems the 'old guys' knew better what they were selling...  ::) 

In any case, the "S" triggers raise the total current consumption for any coils by a little over 80% (averaged over time), because they are ON most of the time. Points are ON (or OFF) for only 50% of the time, while "S" is only OFF for 27% of the time, best case (17% at RPM >4000). This extra "time current" comes straight off of the system charge, showing up as lower operating voltage.

A typical case just wrote me this last week: he has a CB750F with Dyna 3-ohm and an onboard voltmeter. He has long put off long-distance riding on it because of low voltage problems. Last week, he installed a Resistor Pack: he wrote back that the next day his system voltage was over 13.0 volts, and he was finally planning his first long trip, realizing what was long causing the problem. Really, it's just physics...  ;)

OK, now it's your turn:  ;D
I was thinking of one of the AGM batteries for the Hondaman Special #1 I'm building. (Or, maybe for mine, next time around...). Which one replaces the 12N14A for the CB750K, and does it fit? What is the system voltage at full charge? The "gel-cel" batteries out there can let the system voltage rise over 15 volts when cold, which can then damage the stock Honda (15 volt) rectifiers, which then requires a better rectifier...I don't want to get into that routine with a bike I'm going to sell to someone.
See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

Link to My CB750 Book: https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=my+cb750+book

Link to website: www.SOHC4shop.com

Offline KRONUS0100

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Re: Hondaman...this question is for you
« Reply #2 on: August 13, 2008, 06:08:23 AM »
Hondaman...sorry about the delay in response....been out trying to find a new job.  Start cdl training this coming Monday.   Anyhoo......about the AGM battery.  I bought mine from batterystuff.com.............1-800-362-5397 is the order line.  For the 1969 to 1982 SOHC CB750's including customs and supersports.....#YTX14AHL-BS 12 volt.....210 cold cranking amps....$61.00.   And for the the 1969-1978 CB550's....#YT12C....190 cca at 57 bucks.   I forget if shipping was included in these prices...but if not it was not much at all.  These AGM batteries are better than the the so caled gel-cell.  These won't freeze (mine sat out all winter in the barn), and according to the man I spoke to..they can take a sustained 15 volts at charge.   Curiously......what are stock cca ratings of the lead acid batteries?  I know the one I put in mine made a huge difference in starting power and I am going to the big 350cca one they offer for my goldwing.. I hope this helps.  ...By the way.....what is hte cost of one of your resistor packs?  So far I've been lucky I guess.....best not to push it.
MATT
current bikes:  1976 CB750F, 1981 GS1100E
bikes owned:1981 GL1100I, 1990 GS500E, 1981 GS850, 1977 and 1979 GS750, 1974 CB750, 1975 CB750, and a 1982 GS750E

Offline KRONUS0100

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Re: Hondaman...this question is for you
« Reply #3 on: August 13, 2008, 06:17:43 AM »
forgot...my bike typically charges at around 13 even at about 1900....and rises to about 14.6 at 2300 and up.  The lowest reading I got was 12.4 at idle (1000 rpm) but that was before I put the lights on relays and the coils on a separate feed.  Have not taken new measurements yet...still reworking the charging system .....installing a ford solid state regulator and an allelectronics.com 3 phase bridge rectifier.  That should smooth out the charging.
MATT
current bikes:  1976 CB750F, 1981 GS1100E
bikes owned:1981 GL1100I, 1990 GS500E, 1981 GS850, 1977 and 1979 GS750, 1974 CB750, 1975 CB750, and a 1982 GS750E

Offline HondaMan

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Re: Hondaman...this question is for you
« Reply #4 on: August 13, 2008, 12:01:50 PM »
At those voltages, you should consider a newer, higher-voltage rectifier, too. The stock ones were only rated 15 PIV until 1976 (I think), when they went to 25 PIV. The currents will be lower, as the alternator still only develops 210 watts (CB750), but the higher voltage will let it run cooler, which should make for nice, bright sparks and headlight!

I suspected the AGM battery would do this: my next one will likely be an AGM, but after I perfect my new silicon rectifier pack. (another winter project, with the LED timing light kit...  :P ).
See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

Link to My CB750 Book: https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=my+cb750+book

Link to website: www.SOHC4shop.com

Offline 750essess

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Re: Hondaman...this question is for you
« Reply #5 on: August 14, 2008, 04:33:27 PM »
Just wanna throw out another thumbs up for the yuasa agm battey. Running this in mine and have been giving it a beating ironing out some charging ( had it wired wrong ) and efi problems. Using an all in one reg rectifier from electrosport and it holds 13.00 at idle even with the fuel pump and fi parts. Have ran this battery down to 11 many times and always charges right back up. Spins over my 10.5:1 motor very nicely too.
Orleans Cycle Repair and Restoration
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69Z50
XR650L

Offline HondaMan

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Re: Hondaman...this question is for you
« Reply #6 on: August 15, 2008, 05:28:10 AM »
Just wanna throw out another thumbs up for the yuasa agm battey. Running this in mine and have been giving it a beating ironing out some charging ( had it wired wrong ) and efi problems. Using an all in one reg rectifier from electrosport and it holds 13.00 at idle even with the fuel pump and fi parts. Have ran this battery down to 11 many times and always charges right back up. Spins over my 10.5:1 motor very nicely too.

Which EFI are you using, SS?
See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

Link to My CB750 Book: https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=my+cb750+book

Link to website: www.SOHC4shop.com

Offline 750essess

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Re: Hondaman...this question is for you
« Reply #7 on: August 15, 2008, 06:06:28 AM »
600 f4i tb's with mallory external fuel pump and microsquirt controller.
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76CB750F
69Z50
XR650L

Offline HondaMan

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Re: Hondaman...this question is for you
« Reply #8 on: August 15, 2008, 11:18:36 AM »
600 f4i tb's with mallory external fuel pump and microsquirt controller.

Cool! I'm working on a design for using the old Kaw1000 LTD injectors (Bosch) on the CB750K series, probably start with Megasquirt, then design my own controller. I'd like to have a 3-position switch, in the end, for "ECON/NORM/PERF" settings, modifying the off-idle mix foo 15.1/14.7/12.5 air ratios. Alternately, I may try the Chevy Cavalier/Cobalt approach, where going past 3/4 throttle jumps it to 12.5, anyway.

The SOHC4 idles a litle rich. How does your system cope?
See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

Link to My CB750 Book: https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=my+cb750+book

Link to website: www.SOHC4shop.com

Offline 750essess

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Re: Hondaman...this question is for you
« Reply #9 on: August 15, 2008, 11:36:25 AM »
Your right it likes to idle at 12.5:1 according to the wideband. It's still a little uneven but still working on it. You can set the mixture to whatever you want over 12 by 12 table. The microsquirt ( same as the megasquirt by the way but smaller ) can automatically lean out the mixture under cruise and light load and richen under high load automatically by map sensor or by table. Is there a reason for the old bosch injectors and not denso's etc?
Orleans Cycle Repair and Restoration
76CB750F
69Z50
XR650L

Offline HondaMan

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Re: Hondaman...this question is for you
« Reply #10 on: August 16, 2008, 09:23:00 AM »
Your right it likes to idle at 12.5:1 according to the wideband. It's still a little uneven but still working on it. You can set the mixture to whatever you want over 12 by 12 table. The microsquirt ( same as the megasquirt by the way but smaller ) can automatically lean out the mixture under cruise and light load and richen under high load automatically by map sensor or by table. Is there a reason for the old bosch injectors and not denso's etc?

Very nice!
I've been looking at Bosch because of their wide availability. The ones in the LTD are about 10% too much for the 750, but that will let me go to the rich side easier for accel, starting, and idle. After I get the tables worked out in the m'squirt I plan to design a multiport controller to deliver the tabled values. I will need a fast-math CPU for this, and it will do real-time updating via a formulized calc, rather than the RPM-vs-fuel tables alone. Also, doing it this way will let me run it all the way down to 6 volts and potentially tie the Transistorized Ignition I make into this controller, for spark curve control as well.

I've been working on this ever since I did the Ignition design. If I had been smarter, I probably could have charged more for this gadget, to raise funds for the EFI. But, I never thought I'd sell more than 50 ignitions, so I never planned to do it for the $$, just for helping out the riders here.  I suppose more of them need Igniion than EFI, anyway.
See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

Link to My CB750 Book: https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=my+cb750+book

Link to website: www.SOHC4shop.com

Offline 750essess

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Re: Hondaman...this question is for you
« Reply #11 on: August 16, 2008, 05:06:01 PM »
Wow, ambitious project. Will be cool to see what you come up with. I didnt realize those old bosh injectors where still easily available. I'm down to 2.5 ms pulse width at idle, so I could use some smaller injectors. What are the specs? You helped me out a while back with dwell calculations for the built in ignition in the ms, but i never got it fully working. It didnt like being triggered at 35 deg btdc from the dyna pickup. Ran out of time to calc dwell about 4000rpm. I would of had to modify the trigger plate and since it was early in the project didnt feel comfortable cuttin' up my expensive ignition plate at the time, so I switched to the dyna2000 and used the tach output to signal the ecu.
Orleans Cycle Repair and Restoration
76CB750F
69Z50
XR650L

Offline GammaFlat

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Re: Hondaman...this question is for you
« Reply #12 on: August 16, 2008, 05:37:12 PM »
I've been working on this ever since I did the Ignition design. If I had been smarter, I probably could have charged more for this gadget, to raise funds for the EFI. But, I never thought I'd sell more than 50 ignitions, so I never planned to do it for the $$, just for helping out the riders here.  I suppose more of them need Igniion than EFI, anyway.


I'm not surprised the ignitions have sold.  I am SO cranked about the EFI unit.  I don't think it's a matter of if I'll get one, it's more a question of how many.  ;)
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