Ditch the battery?

[F5 Dave]

I would expect the CB is 12V, the deluxe elecy start version was. The XR will be 6V & pathetically small wattage lights & sod all for indicators. the ignition system will be self exciting whereas the CB will require a battery or a capacitor to work. Old two strokes & dirtbikes won't run ignitions that require a battery.

Go ahead & try it but don't be surprised that the tiny capacitor will be sucked dry with the lights on or low revs to the extent that there are ignition issues.

Yes Lin regs are dirty, but SMPS get pretty expensive for dealing with the current you want & bulky & fragile for motorcycle use & why bother when you can just run a battery? Are you really that concerned about the weight?

[xwhatsit]

I would expect the CB is 12V, the deluxe elecy start version was. The XR will be 6V & pathetically small wattage lights & sod all for indicators. the ignition system will be self exciting whereas the CB will require a battery or a capacitor to work. Old two strokes & dirtbikes won't run ignitions that require a battery.

Go ahead & try it but don't be surprised that the tiny capacitor will be sucked dry with the lights on or low revs to the extent that there are ignition issues.

Yes Lin regs are dirty, but SMPS get pretty expensive for dealing with the current you want & bulky & fragile for motorcycle use & why bother when you can just run a battery? Are you really that concerned about the weight?

My reasons for running sans-batterie are stylistic. I want to café my bike -- part of the plan being to remove the battery and airbox and side covers, so there's just an empty space with a carb and pod filter under the seat. I think it looks cool. Others probably do not. Weight is not an issue yet as I scrape the pegs only rarely -- I'm not an experienced rider by any stretch of the imagination.

You might be right about the XR having 6V. In terms of the ignition being self exciting... I'm not sure quite what you mean, but the stator on my bike is a permanent magnet, rather than an electromagnet, so it doesn't need a power source in order to trigger the CDI.

In terms of the SMPS being bulky or fragile, I'm not so sure. You're looking at 30V-12V, admittedly with a high amount of current going through, but there's little SOIC-8 chips that will do that that cost maybe $2-5.

In terms of the bike not having enough juice to get around with all the shiny things switched on, you might be right there. In any case I want to give it a go. If it's infeasible, I'll just make up a little aluminium battery box. *sigh*. It just somehow seems unnecessary...

I put some pics of some ideas. In the flat-tracker there is a much nicer battery box. Note: all pictures are CB250RSs. Don't you think the last pic would look so much nicer without anything under the seat?

[Ixion]

I think this is the look you are after , though this is an SR500.

You are right, the classic cafe racer was a minimalist look. And, indeed, that was the genesis of the cafe racer. I remeber when the genre became popular, and one of the primary drivers was to lose weight , while still remaining (just) within the law. All unnecessary items were removed , mudguards were replaced with aluminium ones (and petrol tanks often also) .

The design yardstick was of course the Manx Norton or BSA Goldstar, and as they were magneto ignition the battery was very disposable

[What?]

Now that you have stated your reasoning...

Here's a couple of ideas that may see you have your cake and eat it:
1/ Make a battery box that looks like an oil tank (or find an old oil tank to turn into a battery box)
2/ Have a single seat with a fibreglass cowl behind it, battery housed within. Or maybe fit the battery under the hump on a GB type seat.

[Eurodave]

Guzzi cafe racers also look really good with their frame triangle empty, but of coarse Guzzis NEED a battery, so they usually get mounted under the swingarm pivot behind the gearbox....

[imdying]

2/ Have a single seat with a fibreglass cowl behind it, battery housed within. Or maybe fit the battery under the hump on a GB type seat.

Yes yes yes, either of these ideas is great. If it were mine, I'd make a 'leather' hump on the new seat (because you need a new seat, the CB is uuuugly), but the hump would be hollow. Get a gel battery that you can lie on it's side and there will be more than enough room.

[Eurodave]

Have a single seat with a fibreglass cowl behind it, battery housed within. Or maybe fit the battery under the hump on a GB type seat.

I do a range of fibreglass cafe/racebike seats.... PM me & we can talk further if you like......

[Ixion]

I like the simple idea, no battery. Why have something that you don't really want.

If it runs OK (and I reckon it would, singles are usually pretty good battery-less, cos they only need a spark every other cycle), then go for it.

At worst it may be lousy at idle with lights on etc. But so, cafe racers never DID run well at low revs , or idle. They were always spitting back through the ruddy GP Amals, and spluttering , and falling off-cam and generally being a pain until they got on the mega. Then it was all worth it.

I reckon that a nice docile , idles nicely, etc cafe racer is a sort of hairdressers bike. Out of character. Might as well have an electric starter.

Clipons, rearsets, good tyres, shorty mega, and it could be a really nice bike. And maybe show up bigger ones in twisty enough roads.

[imdying]

The man makes a good point...

[xwhatsit]

Lol now you see my point of view, I should explain myself better next time .

Yep, it's mainly a stylistic thing, but like Ixion said, it's kind of a simplification process.

I'm definitely leaning towards the GB500 leather-hump single Jap style seat. I never thought that you could fit anything in the hump though. Also in terms of reducing the size of the battery -- ideally a move to a lithium-ion battery would work brilliantly but unfortunately that would mean a lot of extra charging circuitry. Will have to read up on my batteries and find an easily-chargeable compact 12V.

The oil-tank idea I like as well. Interesting idea on the Guzzi, Eurodave, I wouldn't have thought there'd be anywhere enough room there. Will have to take a look.

Lol, well Ixion, my bike (well at least when it was running before) fit many of the criteria you listed -- bitch to start, always having to blip the throttle to stop it stalling, crackling and popping on overrun due to air being sucked through the cracked head...

Yeah, I've been looking at the other parts bike in my garage, and trying various seating positions with bits of plywood. I think if I had a café seat and clipons, I'd probably need rearsets just to be comfortable, at almost dead on where the pillion pegs are. The gear linkage looks easy -- just a longer pushrod, but the brake looks a PITA. Will have to shorten the rod I think, and I'm worried about it being in the way of the kickstarter (oh well, more bump starting then ).

Just rambling now.

Thanks for your thoughts.

Oh and I think I must have really good night-vision anyway, lol. I did my commute at 11pm home from Remmers to the Deep South (well, not really, just over the border) without a headlight, and didn't notice until I pulled up to my garage and couldn't see shit. Good thing I had a brakelight, no?

[avgas]

Never had a battery on the TS. And i rode that on/off road for about 6 years. Lights, indicators everything still worked as long as the motor ran. The guy laughed when i had to start the bike to do the wof though.

[davereid]

Dump the battery. Ixions onto it, put a decent size capacitor in and everything will run fine.

On a car alternator, or some large mo.bikes, the alternator relies on magnetisim created by externally excited windings. So the voltage regulator turns these windings off, when the voltage reaches 14 (ish) volts, to keep it all at acceptable voltages.

On little bikes, the alternator has fixed magnets. The faster the engine goes, the faster the alternator spins, the more juice it provides. To stop these going overvoltage, the regulator is just a big heat sink - it diverts some of the current into itself, creating heat and keeping the voltage down.

So, if you find the bike runs fine at idle, try it with the lights on. Still OK? then just leave the lights on - they will assist using up a few joules that the v-reg wont have to turn into heat, particularly at higher rpm.

But the key point is, the battery once fully charged will draw very little from the alternator. So, the regulator has to do all the work, and this applies even if the battery is there.

Another idea - build yourself an auxillary regulator - one that cuts in at say 13.8 volts and does some of the work for the main regulator. pm me if you need a design.

[xwhatsit]

Dump the battery. Ixions onto it, put a decent size capacitor in and everything will run fine.

On a car alternator, or some large mo.bikes, the alternator relies on magnetisim created by externally excited windings. So the voltage regulator turns these windings off, when the voltage reaches 14 (ish) volts, to keep it all at acceptable voltages.

On little bikes, the alternator has fixed magnets. The faster the engine goes, the faster the alternator spins, the more juice it provides. To stop these going overvoltage, the regulator is just a big heat sink - it diverts some of the current into itself, creating heat and keeping the voltage down.

So, if you find the bike runs fine at idle, try it with the lights on. Still OK? then just leave the lights on - they will assist using up a few joules that the v-reg wont have to turn into heat, particularly at higher rpm.

But the key point is, the battery once fully charged will draw very little from the alternator. So, the regulator has to do all the work, and this applies even if the battery is there.

Another idea - build yourself an auxillary regulator - one that cuts in at say 13.8 volts and does some of the work for the main regulator. pm me if you need a design.

Thanks for that info. Bike definitely has fixed magnets. The brutish-looking linear reg has a big enough heatsink on it to cool my old C64.

The lights-on idea sounds interesting to me. The cap wouldn't take long to get charged up, and then the reg would be copping it a fair bit. An auxiliary reg isn't a stupid idea either -- didn't think about a voltage low-pass on it to share the load. That's a very smart idea. I might ask you about the design of that at some stage; 90% of my knowledge is in digital circuits, and the other 10% on enough analogue stuff to make the digital stuff not fry.

I think what I might do once the engine is repaired, is to take my multimeter and just have a bit of a poke around at various RPMs to see what's going on.

[Ixion]

Um. I think I said a 1000mF capacitor. On reflexion, it may have been 1000 microfarad. Bit of a difference I know, but this was thirty years ago. I may still have one, I'll have a look round. Just that a one fard capacitor would be bigger, a lot bigger, than I recall.

[xwhatsit]

Lol! I mentioned to a fellow Compsci that I was going to have to find a 1 farad capacitor and he just about shat his pants... he told me he wasn't going anywhere near it, and to wear oven mitts while shorting it out with a screwdriver, hahaha. Yes, 1000uF seems a bit more practical. But if it's bigger than what is required, it doesn't really matter. I'll just get the biggest one I can find and reasonably mount.