Part 6. Amping up the electrics on the Spark-atana

Once again, this build is asking all sorts of questions that not many people have the answers to!

Once again, this build is asking all sorts of questions that not many people have the answers to! This time, we’re left mulling over the right way to go about designing and installing the electrical bits – you know, the bits that don’t work on petrol, but that other magic energy stuff that comes from the battery thing. Are you sensing cluelessness?…


4 stroke race-bikes from 1982 didn’t come with complicated electronics. Let’s say the Katana of the day had 4 spark plugs, 2 coils, an ignition pick up and maybe, an electric tacho and starter motor would have been about it.


So why will this Katana Racebike need anything different? Well, there’s one important and incontrovertible reason we need to divert from the minimalist electronics of 1982 and that is simply this; we race at night.


Night, means lights. Lights mean more power, and more power means heftier generators, batteries and supporting systems. BUT! I hear cries of “Given this motorcycle left the factory with a generator on board it’s not much of a problem is it?” Well, let’s take a holistic view of this racing motorcycle’s overall performance and purpose for a moment.


True enough, we could generate using the system Suzuki designed. That’s the same system I saw give up the ghost in front of my own eyes at last years race, on the GSX1100 that Bob Chambers and Peter Boast used. A useful reliability warning!


Beyond the proven durability issues, consider the effect that Suzuki’s OE 4lb flywheel has when stuck on the end of our race engines crank. It adds a huge amount of power-sapping weight right where you don’t want it, and also sticks out so far it almost needs a furniture castor on it to help the bike around corners! But we’re not done with just those reasons – oh no! Also consider the effect that the generator’s heat has on the oil temperature. On our GSX1100, the generator runs in the same oil as the engine, clutch and gearbox. The GSX1100 OE 3 phase generator has it’s fair share of detractors that dislike both it’s fragility and incredibly hot running temperature.


It’s dark, we need lights – this is one of the best lit portions of track too – the finish line.

It’s dark, we need lights – this is one of the best lit portions of track too – the finish line.

It thus makes sense to get it off the crank, out of the massive side casing, reducing the inertia on the crank, increasing power, increasing ground clearance and also to get the extra heat out of the oil, which will already be working at it’s limit in a 4 hour endurance race.


Needless to say, before we decided anything else on the electrics, we got rid of the generator/flywheel combination for all the reasons above.


So, if we’ve stopped generating in the way Suzuki wanted, where do we put a generator now?


Well, the first question I asked – do we need a generator at all or just a really BIG battery? Good question, and the answer, like so many things on the Katana depends on answers that not many people have! So, I had a think and started investigating what may be possible.


Sensible lighting for a race that happens at night goes like this – a) build them bright, and b) build them with something the aviation industry calls “system redundancy” – to you or I, that’s better described as “at least two lights, in case one goes out”


The Katana has a H4 fitting in the headlight, for which off-road only rally bulbs of up to 160/90W are available cheaply (that’s 135W more power than stock 60/55W H4 bulb). In concert with a pair of spotlights I’ve acquired which use H3 bulbs (55W stock, 130W available) there wouldn’t be much of Spa left unlit! That’s the first and second boxes ticked.


So, let’s do some maths to see what current these would need to make them work  – 2 x 5W tail-lights, 1 x 160+90W headlight (both filaments work when on high beam), 2 x 130W spotlights, plus a few watts here and there for rev counter and small dashboard lights. What’s the total current for that? Well, o-level physics and distant memories of ohms law tells me that Amps must be Watts/Volts, so Amps = 520/12. That’s = 43ish. Throw in an ignition system that has a 5 amp fuse, so let’s say that draws 3 amps (until we measure it that’s a guess), and we’re at nearly 47 amps – that’s quite a hefty draw.


Can we supply that kind of current solely from a bike battery for the 2 and half hours that this race runs at night? (Battery only electrical system is what racers call “total-loss”) Well, nope. Although we do have stops every 45 minutes, we don’t really want to be changing batteries as well as fuelling – although, ruling nothing out, we could if we needed to.


A standard heavy old-tech Lead/Acid battery that will fit under the seat might give us 14-20 Ah (amp hours) which basic maths tell us at the 20Ah rating and assuming a 40 Amp draw would give us 30 minutes of use before being emptier than a politicians pre-election promise. Truthfully, it’ll give us a hell of a lot less than the amp Hours advertised. We’ve got to start the bike twice on the grid in the warm-up start procedure, plus there’s heat and vibration which take us away from ideal lab conditions for a battery and into something altogether more hostile.

More importantly though is something called the Peukerts effect – the battery’s Ah capacity decreases the higher the draw you make from it. Peukerts effect comes complete with it’s own reasonably complicated equation to work out what your “Peukerts” number is. , 2 identical capacity batteries with different Peukerts numbers will discharge at different rates, the lower the Peukerts number, the better the battery will retain charge at higher rates of discharge. Complicated huh?


The batteries won’t give you all of the amp hours shown on their rating if you’re making a really heavy draw (Amp hour ratings are calculated using the draw it would take to completely flatten the battery in 20 hours, which for this battery would be just a tiny 1A load), and we’d be left with a Katana to push home embarrassingly early in the race once we’d switched the lights on!


So, if we ran using 1982 Lead Acid technology, we’d need a generator. Definitely. But…it’s not 1982. Today’s battery and lighting technology both boast significantly better performance, so what if we dragged both of these bang up-to-date? Could we run generator free then?


Technically, we’re not allowed to use lights that aren’t period. BUT – I have been reading rumours that my very favourite Endurance stalwarts who shall remain nameless (let’s just say they’re 2 less than 3 phase) aren’t allowing that to get in the way of them running low energy LED lights in the same series as the Kat this year. I think the ruling can be interpreted that a conventional headlight of the time, with an LED powered bulb, will be ok, whereas an aftermarket LED lighting unit, or projector beam/HiD light, looking nothing like the original, would not.

Low energy H4 LED bulbs ARE readily available, but there is a problem. From what I can see so far, there isn’t a reliable, standardised comparative rating for conventional bulbs and their LED counterparts, so proving that your purchase will be as bright as any kind of H4 bulb (even the standard 60/55W, let alone the 160/90W rally bulb) doesn’t seem possible. It’s all well and good saving loads of power, but will we be able to see where we’re going! This is also very important let’s not forget.


Standard lights measure their “power” in Watts, whereas for LED, Wattages are all over the place, if mentioned at all. Watts has bugger all to do with the amount of light they put out anyway, it’s only a power consumption figure…

I’ve seen listings for “50W LED bulbs” actually rated as drawing only 6W of power in the technical specifications. Messy. Welcome to the new-technology method of selling – get the biggest number you can wedged into the sales patter somewhere. Worry later if it can be justified.


Sensibly LED’s often adopt “lumens” as the preferred choice for quantifying their effectiveness, which being a measure of the actual output of light, would be a very useful standard to adopt across all lighting mediums. But standard bulbs don’t rate themselves by it, leaving us without a benchmark to work out comparative lighting strength.

Specialist lighting forums I’ve visited (yes, really, they do exist) declare that even the humble common all garden 60/55W H4 car bulb can vary in it’s output from under 1000 to as much as 1800 Lumens, so it gets really messy trying to compare apples for apples.


Then there comes the issue of batteries…


Li-Ion batteries are amazing, they weigh diddly squat, they’re tiny, and yet they have the cranking power to turn over really huge engines. Oh, and you can leave them all year without any kind of charge and they have lost so little that you’ll still be able to start your bike. Add to that they charge from flat in minutes, have 10 times as many life cycles as a Lead Acid, and what you have is an incredible bit of kit.


Well, yes, but there are some hidden challenges lurking therein for our particular type of use.


You see, take a Lead Acid Battery with 20Ah of capacity. That’s likely to have 270CCA (cold cranking amps) of va-va-voom available when it comes to starting your motorcycle. Big twins, like BMW GS1200, or KTM Superduke take a LOT of CCA’s to get them going. All batteries therefore use the CCA rating as a very important sales metric.

The Li-Ion battery manufacturers clocked on to the fact that the Amp hour ratings of a Lead Acid and Li-Ion Battery with a given CCA rating weren’t the same. Not even close. It’s just the way they work that means lets say a tiny 8Ah Li-Ion battery will give you the same Cold Cranking Amps as a 24Ah Lead Acid item.


Problem being, that nobody wants to buy an 8Ah battery when you have had a 20Ah one. It may be able to do the job just as well, but it’s smaller, less value, more problematic (in the buyers mind at least)

So, what did they do? They didn’t want to lie to us (or perhaps more accurately, couldn’t) so they invented a useless sales metric for Li-Ion to baffle us – the PBEQ Ah or, the Lead Acid Equivalent Amp Hours.


At this point the Ah rating ceases to be about what the battery can supply capacity wise, and has more to do with matching up the Cold Cranking amps between a smaller Li-Ion battery and bigger Lead acid one.

This means my chance to look at Li-Ion and understand what capacity they actually have has just been wiped off the literature to be replaced by sales driven bollocks.


Much like the bulb situation, the change from old tech to new tech has caused confusion because of a lack of comparative standard (or the unwillingness to adopt it as the sales may suffer…) Buying this stuff is akin to taking a swim in a pond of deliberately muddied water, where the hungry crocodiles from the new tech companies will try and pick you off with language and ratings that have little or no useful equivalent.


So! – Screw all that – What this needs is testing! The modern tech stuff is still the way to go, the only thing we’re unsure of is how good it will be


I’ve just taken the plunge and bought all the modern gear that is apparently best suited to our plight. Once it’s all fitted we’ll run the things to see if a) I can see ok and b) the electrical system we plan to run will power them for long enough to finish the race.

  • 1 x main headlamp H4 LED bulb – rated at 3200Lm or approx double standard H4 – 40W power consumption claimed (around a 1/5 of equivalent standard bulb)
  • 2 x spotlights H3 LED bulb – rated at 800Lm – 7.5W of power consumption claimed
  • 1 x 1157 fitting rear 9 LED red cluster (brake light equivalent) tested at 0.4W power with “both” filaments working
  • 1 x 1156 fitting rear 9 LED cluster (number plate light equivalent) not tested, but assumed to be a bit less than the above which is a slightly stronger bulb.
  • 1 x Skyrich battery – YTX14 equivalent (we will be buying another one of these to wire up in Parallel once we’re happy with it’s performance – creating a power pack with the same volts, but double the capacity)

Oh, and I haven’t even mentioned alternators…I”ll leave that for another part, as that is another HUGE subject on it’s own. Just to say, we will run one, I have bought it, and even though we may not even need it subject to testing (although I think we will), it’s there as an added security – system redundancy again! The challenge with the alternator is how to drive it from something that wasn’t meant to drive it…


Why is nothing simple?! (some people close to me have started to ask the question if it’s me that’s making everything complicated – really! Mind you, I’m starting to wonder if they have a point….)

Part 7. The engine…strip and specification

When the big GSX1100 engine we’re using in our Katana left the factory 32 years ago,  it was by contemporary standards, already a monstrous powerplant. You’d have struggled to find anything better in a road bike in 1982 and even by today’s standards, it’s far from breathless.