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my bike had this mod, still did it
my brand new 12000LC did it exactly the same - but they had further developed the idea and whenever it wouldn't start they turned on the heated grips too (they got that bike back to keep)
my KTM did it

what you find is when you fit an aftermarket battery that is designed to last longer than one day after the end of the warranty period, you never have the problem again
 

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2012 BMW K1300S (also 1993 BMW R1100RS and 1974 BMW R60/6)
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...I had pretty good luck by switching to an Odyssey PC680 battery which cranked hard hot or cold. But the quality on those seems to have gone down, or at least they don't seem to last as long for me as they used to.
I'm not an electrical engineer but my gut and experience makes me think the battery compartment size imposes a limit such that anything that fits will be barely capable of the required service.

Which is OK for weight reasons if nothing else, but only as long as tolerance stack-up doesn't fall into the inadequate zone and in-storage maintenance is performed competently -- which is something I keep screwing up, but at least for a different reason each time.
 

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The PC680 is slightly larger than the stock battery, but a bit shorter. A little bit more with the optional metal jacket.

There's lots of room for the GT battery, as the battery shelf is only on three sides (it's open to the fuel tank area).

The PC680 just cranks harder than the BMW AGM battery.

As I said, I've had a lot of good luck with them for more than a decade, but more recently they just don't seem to last as long. They still crank the bike over quite strongly though.
 

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Dagnabbit, I got my state-required annual Safety Check today but then the bike wouldn't start. Tech was kind enough to give me a boost. His portable power pack didn't make any difference, but the larger, plug-in-the-wall battery charger/booster spun up the bike with no problem at all. My PC680 is 5 years 3 months old and was load tested by the selling shop (specializing in batteries) and found good, just a few months ago. I haven't been riding much, so I guess the solution is to 1) ride more and 2) buy another PC680. Low price hereabouts is about $120, pretty good, the last one was $150.

Stolen from elsewhere:
CCA or Cold Cranking Amps is defined as "the current a fully charged battery can deliver for 30 seconds and maintain a voltage of 7.2 volts (12 volt battery) at a temperature of -18°C".

PHCA or Pulse Hot Cranking Amps is "the current a fully charged battery can deliver for 5 seconds and maintain a voltage of 7.2 volts (12 volt battery) at a temperature of -18°C"

Looks to me near meaningless until/unless it's pretty da*m cold where you are. Manufacturers can by design increase CCA ratings, at the expense of duration. If your engine doesn't start within 5 seconds, you have other problems.

HCA (Hot Cranking Amperes) is a measurement of the current a fully charged battery can deliver for 30 seconds and maintain a voltage of 7.2 volts (12 volt battery) at a temperature of 26.7°C (about 78°F). HCA is a rating specifically geared towards starting applications in warm conditions as the warmer the temperature the more available power from the battery. But try get HCA ratings from your battery seller...
 

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As far as I've read you'll need the following tools: T25 screwdriver, heat gun for shrinking insulation over new connectors, crimper/solder gun/torch for terminals on new wire, 10 mm socket w/ratchet drive or electric driver for 10 mm.

Remove battery compartment cover, fairing top (over "gas tank"), also right and left. Confuse the screws.
Unbolt (forget size) and remove the fuel tank which should be near empty so as not to spill gas.
While you're at it, replace the stock plastic quick fuel disconnect on the gas tank with aftermarket metal.
Install new wires from battery to relay, relay to starter, either replacing or in parallel with stock wires.
Reinstall fuel tank, battery compartment cover and fairing bits.
Go ride, be happy.
But I haven't done it yet, not looking forward to the better part of a day playing with the plastic, etc.
 

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Hot Start Mod - The Cheap and Nasty Edition

OK, if you're of a nervous disposition, stop reading now. Trigger warning :oops::)

I got the dreaded hot start issue this week. Bike was warmed up and I stopped, turned off the bike. I decided to move a bit, so turned it back on and the starter would hardly turn. Classic hot-start behavior. I left it for 5 minutes and it spun and started no problem. Admittedly, the battery is 5 years old, but appears fine otherwise.

So, with time to kill on Friday night, I took off the tank, and had a look at the relay. I had some 2.5mm wiring to hand, from an old electric tow winch, which used to carry the full load from a battery to the winch, so I thought, since I'm adding it to the existing wiring it should make a difference.

I crimped a lug to one end, heat shrunk it. this was going on the positive terminal (after the other end was secure, I'm not daft :) ). Looking at the relay socket, the female, embedded ends are crimped on, with part of the crimp accessible. So I used a thin screwdriver to force it open, slipped the other end of the wire in and crimped it shut with a needle-nose pliers. Did the same for the wire from the relay to the starter motor. I didn't take the female terminals out.

So in essence, beefed the existing wiring from the battery to the starter motor by 2.5mm. The relay looked ok, and was heavier than any others i had to hand, so I left it alone.

Back together, the starter motor appeared to spin a lot healthier and faster, but you know how a cleaned bike goes faster?

But, luckily, my mate as an almost identical K1200GT, which also displays the problem, and we were going for a spin yesterday.

Going through a town, the cooling fan was cycling, so we knew the bikes were hot. We stopped and turned off the bikes. He tried to restart his...nothing. I tried to restart mine, and it spun and started immediately. We repeated the procedure with the same results. Pretty good empiric evidence of a successful mod.

The good...... I think I proved that the mod I did works. As I said, it is at the cheap and nasty end of the spectrum for the hot start mod. Buy the officially approved BMW loom if you want.

The bad....... My mate now wants me to do the same to his bike - more work for me. He'll buy me beers as payment, so I'm happy enough.

All in all, about 3 hours work, but I am used to taking off the plastic, and was taking my time.. Tip (which I learned here) Get a big piece of cardboard or similar, draw outlines of the fairing panels, battery compartment, etc. and as you take the fairing bolts off, push them through the cardboard in their respective positions. This prevents the hassle of putting back longer bolts into shorter, blind holes etc. And keep it as you will need it again :)
 

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Good on ya for doing the mod. But what I wants to know: does the relay in the factory rewire kit have a higher amp rating that the original? I know they have different part numbers, so "something" is different, could be subtle, could be more. This is faintly related to the results: a higher rated relay may pass more current and be a significant(?) part of the solution... but it's likely a handful of dollars more expensive than the stock unit.
 

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Isn't it interesting that a simple hunk of wire can make such a difference! BMW been kinda bad about barely big enough wiring components for a long time. Clear back on the R100 bikes a problem with too small grounding wire from the diode board caused all manner of charging issues.
 

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Just wanted to report back and say, after a 90 minute ride yesterday, the mod is really working. The bike starts instantly and you can definitely hear that the starter motor is getting more juice. Definitely worth doing when you've a spare afternoon.
 

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Just an update. Finally got around to doing the same quick and dirty mod on my mates K1200GT, which was displaying the issue a lot longer than mine was. He rode it home and left it running until the fan came on. Turned it off and it immediately started up again on the starter. He's delighted as this is the first time it's done that.

So that's two for two successes.
 

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And a final note, just back from 3 weeks biking in Italy, where temperatures were in the mid 30's (95 F). The bike was hot all the time and never once failed to start. In fact, the speed of the starter motor was noticeably robust.
 
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Just wanted to report back and say, after a 90 minute ride yesterday, the mod is really working. The bike starts instantly and you can definitely hear that the starter motor is getting more juice. Definitely worth doing when you've a spare afternoon.
You dont fancy flying over to East Midlands and doing mine, do you ? ;)
 

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Sounds like a very sensible option - rather than the £175 BMW charge for the kit.

I want to do this mod - as I'm having the same issue - Vmax's have the same issue and easily cured by adding heavier duty cables - I think I bought a kit from Vmaxbitz for about £30.


Please could you clarify : the heavier duty wire is from the Positive Terminal of the battery to the starter relay ?

Thanks

Stu
 

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Hi Stu, yes, I ran a heavier cable from the positive of the battery to the relay connection. I just opened the crimp on the connector (holding the existing wire in) and used it to clamp the new wire. This was easier than trying to get the connector out. I then ran another wire from the relay connector to the nut on the starter motor. I crimped on a circular terminal and held it down on top of the existing wire.

It is easier to see which wires on the relay connector to beef up, as they are already the two thicker ones. The other two are thinner and are the ones to active the relay. These can be left alone.

So, in all you are running 2 heaver wires. One from the positive terminal to the (incoming) relay connector, and the other from the (outgoing) relay connector to the starter motor. It is pretty obvious when you're in there, but do come back with questions if you need to.
 

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Excellent - Thankyou so much - I'll be doing this as soon as I get some heavy gauge wire. and a dry afternoon :( Many thanks.

You don't recall how long I need to make the cables > - there again I have a K1300S - so may be a difference.

Cheers

Stu
 

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The one from the relay to the starter motor is around a foot. What I did with the other one is connected it to the relay then ran it up around the airbox/whatever route is convenient, then cut and crimped on a ring terminal. It was no more than two feet IIRC. You will have more than enough wire, but remember to get two ring terminal as well, one for the starter motor stub, and one for the battery terminal. And heat shrink tubing for the professional look. :)
 
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