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Discussion Starter · #1 ·
Bike (or at least the engine) is a 71 SL 350.
Okay, so I know this has been discussed before. I know the accepted answer is you need a battery. But there is that troubling sentence in the manual (which of course I can't find just now) which says the bike can be started with the kickstarter if the battery is dead. I've NEVER personally been successful when trying to do that with my other SL, but I did read it in the manual. :rolleyes: Since my current project will not have lights or any electrical equipment except the ignition system and a simple kill switch (button), I'm leaning toward adding a capacitor in place of the battery.

Saving weight is not really my goal, but rather merely simplifying my system and elimination of potential trouble spots... such as a dead battery and the need to keep it charged. Interested in any and all thoughts on the matter.
 

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Discussion Starter · #2 ·
Hmm, anybody??? Hellooooo? :-?

How's this (over) simplified diagram look?
Simple-wire-diagram.png
 

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There is no way the stock stator can put out enough juice to run the bike without a battery. Not if you want it to be street legal (e.g lights and all)
The manual may have meant "if your battery is too low to use the electric starter"
 

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Sensei
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With the rectified alternator output and a decent sized capacitor, the bike CAN run...But not as well as it will with a battery......The trick is getting it started ......
 

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Discussion Starter · #5 ·
There is no way the stock stator can put out enough juice to run the bike without a battery. Not if you want it to be street legal (e.g lights and all)
Well... I don't want it to be street legal. It won't be and is not intended to be. As stated, there will be no lights, etc. only the ignition system. ;)
 

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I can 'run' my 175 on two biggish capacitors, just placed where the battery would be. But no lights, I have thought you could use the split in stator output to run a dual capacitor / battery set up. So 2/3 of the power went to the caps to run the coils and 1/3 went to a small lead acid to run the lights. But never got around to actually doing it
 

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With the rectified alternator output and a decent sized capacitor, the bike CAN run...But not as well as it will with a battery......The trick is getting it started ......
The trick is to kick it over a few times with the ignition off first to "prime" the cap then flick the key to run and quickly kick it
 

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A common misaprehension. When the engine is running, the alternator provides all the necessary electrical power necessary. The battery is merely a resavoir to provide power for the starter motor and sufficient to power the coils. If your alternator was not sufficient to power the machine, you would soon gring to a halt once the battery was drained.
In this situation, a much smaller battery can be used, both physically and in amp hourage, it only has to power the coils at initial start-up.
 

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This concept works better on more modern bikes that don't have partial - loss charging systems like these old Honda twins do.

If you do the stator - bridge wire mod, and run no electric accessories or lights, and use a modern MOSFET reg/rectifier unit, then it should potentially work on your 175, but below about 3krpm, you will be gradually draining the charge back out of the caps faster than they can be recharged.

If it's a track/race bike then this is a non issue though.

Sent from my SAMSUNG-SGH-I537 using Tapatalk
 

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Sensei
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When the engine is running at a rev rate sufficient to produce as much or more energy than is being used (which does not occur until well above idle), the alternator provides all the necessary electrical power.
The battery is merely a reservoir to provide power for the starter motor and sufficient to power the coils. If your alternator was not sufficient to power the machine, you would soon grind to a halt once the battery was drained.
In this situation, a much smaller battery can be used, both physically and in amp/hour capacity, it only has to power the coils at initial start-up and at very slow revs/idle
jjdugen.... Just trying to clarify...If you disagree with the changes I've made, let me know and I'll re-edit this post.....
 

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Back when I was in high school, I followed this article by Gordon Jennings and applied it to my strictly off-road (no title) SL90 that I bought with a bad rod, sent the crank to Powroll and had it stroked 1/4", bored it to S-8 (52mm) so the final displacement was 110cc (broke high school kid had no money left over for a good camshaft and bigger carburetor, but my Mom did let me assemble the bike in our Florida room during the winter :D ). The energy-transfer design worked just fine on my SL90 and Jennings made it work on his CB450 road racer at the time

http://www.ohiocaferacers.com/GordonJenningsETMagneto.pdf
 

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Not trying to hijack the thread...but would a small 12V sealed lead acid battery work instead? I'm referring to inexpensive batteries used in home security systems for example. They're small, cheap, and could be easily installed about anywhere. Say, something in the 3.5-4.5 ah range? Like oupa, I intend to have absolutely minimal electrics on my bike - an LED headlight and tailight only to be legal for daytime rides.
 

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Sensei
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Butch, the amperage requirement per ignition coil is 2.4 amps and they charge and discharge separately, so no usage overlap....

Herein lies the problem..... your charging system will be attempting to push 13.2+ Volts at 150+ watts (at high revs) which is 12+ amps back into the battery to recharge it, and the battery was designed to accept a milliampere charging rate......It's going to get very hot, very quickly......

Similarly, the small Lithium batteries tend to require exacting Voltage and Amperage limits, to which the stock system does NOT adhere.....Flaming Batteries anyone?
 

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Discussion Starter · #14 ·
.....Flaming Batteries anyone?

No thanks! Been there before. :(
To be totally clear, this is a track bike. There will be NO lights of any kind. Not even instrument indicators or illuminators because there will be no instruments! No headlight, tail light, brake light, blinkers, no horn, no e-starter, no keyed ignition switch!
The only thing the charging system will be feeding is the ignition system. ...and those appliances to (I hope) make it work without anything bursting into flames or melting wires. The one non-ignition related device will be a (very) simple kill switch... which I suppose is technically a part of the ignition system. :-?

The goal is to make the system as simple as possible. The bike will most likely get little and VERY infrequent use, although it may also be pulled out on short notice. To that end, I really don't want another bike sitting around on a tender just to be sure the battery is ready when I am. Another consideration is not having a battery to worry about in the event of a crash. No battery means no fluid spills and nothing to short out. Yes. I am aware that a properly housed and restrained battery should not be a concern in that regard, but no battery is even less concern. ;)

Since I have no fantasies about winning races or doing much more than contesting for last place as a 225 pound guy on a 350 against 500's & 650's, I am not trying to conserve weight! My goal, as mentioned, is to make the system as simple and user friendly as possible. I've read some on the subject but I am no electrical whiz! I've consulted several people who are electrical whizes, but they know nothing about mid-70's Honda twins! My major concern is that the accepted thought has been that these bike's alternators do not produce enough power for this application. I've made the decision to try it. :cool: If it doesn't work, I can always stick a battery in later. If however it does prove to work, we gain one more tool in the old Honda box. :D

I'm not going to be to that point in the project for sometime, so keep an eye on this space or my project log for the final results! :cool:
 

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There you go oupa.......20,000 uF and you should be fine......
 
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Hi 66Sprint. Yes, I will accept your corrections on a STANDARD stock regulator and rectifier. But fit a modern three AC input rec/reg unit and, at least on my 350, there is ample output to sustain the electrical system, even at tickover. I have a voltage meter fitted to monitor the health of the charginging system, 12.8v at 1000rpm rising to 13.6 with lights, 14.2 without after about 1 - 2000 rpm. I am running a lead acid 'refillable' type battery at the moment but will spring for a sealed gel type when I've finished all the other niggling jobs that go with recommisioning a fifty year old machine.
 

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jjdugen..... I removed the extra "6" from my username if you wonder why I edited your post.....

So far we agree, as the original stock system equilibrium point for charge/discharge is somewhere around 1800 RPM.... I was not surprised the output @ rpm improved with the modern unit, as any good modern combined rectifier/regulator is a significant improvement over the stock/original ones.....
( I don't wish to re-enter the discussion as to the reasoning behind using a three phase R/R with the Honda's single phase output, we all know that it can and does work)

My post was primarily to warn against using too small (Ah) or the wrong type battery if you choose to run a battery.....

I believe that oupa will likely just wire in adequate capacitance and run battery-less as it is simpler and suits his purposes....
 

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Discussion Starter · #19 ·
There you go oupa.......20,000 uF and you should be fine......
I've already bought some 47000uF 50V capacitors (as specified by some guy in India via the reliable resource of youtube :eek: ). They were ridiculously inexpensive so the old adage, "nothing beats success but failure" will be tested.

Since this entire project is basically a series of experiments and learning experiences, I've decided to include this one. Whether I soar with eagles or crash and burn, you all get to benefit from my mistakes... and occasional successes. :cool:

Wish me luck! :D

BTW Steve, I'll take that as a quasi endorsement. Something I value given the source. ;) ...please don't tell me if you were just being facetious. :grin:
 

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Bike (or at least the engine) is a 71 SL 350.

Saving weight is not really my goal, but rather merely simplifying my system and elimination of potential trouble spots... such as a dead battery and the need to keep it charged. Interested in any and all thoughts on the matter.
You can rewire the alternator to turn it into an energy transfer magneto system. The CL350 that won the Baja back in '68 had that done and its a common dodge on road racers too. Cycle magazine did an article on how to do it for the CB450 racer. I've got a copy of the article at home (on the road for business right now).
 
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