Yamaha TRX850 Enthusiasts Forum

Hi,
I have started doing a few track days, and am now looking at how much road gear (weight) I can ditch. Yes I know I should just eat less, run more, but this might be easier on me. The question that I have is, if I am willing to push start the bike, and the alternator is still working fine, can I whack in a lightweight battery from Supercheap, 'Century 12v 2amp' that weighs stuff all. I was thinking that I could use this to 'smooth' out the power from the alternator, and given that there is no lights or starter motor to run, I should get away with it. It also means I could mount the battery forward, where the headlight used to be, giving me more weight over the front. What I don't want to do though is stuff the electrics on the bike, or have the battery explode / catch on fire at the worst moment.

Any thoughts?

doug78 wrote:Hi,
I have started doing a few track days, and am now looking at how much road gear (weight) I can ditch. Yes I know I should just eat less, run more, but this might be easier on me. The question that I have is, if I am willing to push start the bike, and the alternator is still working fine, can I whack in a lightweight battery from Supercheap, 'Century 12v 2amp' that weighs stuff all. I was thinking that I could use this to 'smooth' out the power from the alternator, and given that there is no lights or starter motor to run, I should get away with it. It also means I could mount the battery forward, where the headlight used to be, giving me more weight over the front. What I don't want to do though is stuff the electrics on the bike, or have the battery explode / catch on fire at the worst moment.

Any thoughts?

Have you tried bump starting a TRX on a flat surface?

Are you planning on converting to a full on track bike or do you want to be able to go back to a road bike?

The bike can go on a serious diet if you are planning to track only. You could (assuming you can start the bike) go to a total loss system, cut off the rear subframe, design a light weight fairing bracket, lightweight race bodywork, cut the loom, fit light wheels, fit a Ti 2into 1 exhaust, carbon clipons etc etc

If you wanna leave the bike for road use, just buy some race bodywork, sticky tyres, FCRs and a race exhaust and don't mess about with electrics. Wheels make a hell of a difference but cost big money

You might find you're running more anyway if you try and bump it, ha ha

If you're really, really serious about running a smaller battery you could probably get away with a battery eliminator (big capacitor and a resistor wired in parallel) The capacitor has the same 'smoothing' effect as the battery but obviously won't hold a charge for more than a few seconds at the most. The resistor is there to provide a load for the reg/rec. Not exactly total loss as you still need the alternator to power the bike but at least you'd lose a few kg of unsightly fat... Total loss still needs a battery to provide power to the ignition but you can do away with the generator windings, thus freeing up 0.0000000000000000000000000000001 bhp.

You could probably cobble up a starter from a cheapo 4t pit bike and a go kart wheel

Kayla wrote:You might find you're running more anyway if you try and bump it, ha ha

If you're really, really serious about running a smaller battery you could probably get away with a battery eliminator (big capacitor and a resistor wired in parallel) The capacitor has the same 'smoothing' effect as the battery but obviously won't hold a charge for more than a few seconds at the most. The resistor is there to provide a load for the reg/rec. Not exactly total loss as you still need the alternator to power the bike but at least you'd lose a few kg of unsightly fat... Total loss still needs a battery to provide power to the ignition but you can do away with the generator windings, thus freeing up 0.0000000000000000000000000000001 bhp.

You could probably cobble up a starter from a cheapo 4t pit bike and a go kart wheel

You could make one up with a crank handle, nevermind engines.

I honestly think maybe regular exercise would be easier...

Thanks for the help thus far, however if I still want to push on and do this, is anything going to blow up on me?

Maybe just the capacitor if you wire it up backwards (big pop and a shower of polystyrene!), but the electrics will be fine.

Seriously, have you tried bump starting a TRX?

Yeah, I had a issue with a battery and cash flow problem when I first got it, so I very quickly became the king of finding hills to park on! I have also just started it in my flat drive, third gear, run about five steps, dump the clutch and then whip it in flipping quick!
However it is all sounding like too much effort right now, the joy of work and family time.