Try flux core solder and tinning the tip of the iron and melting a blob of solder on it. This will evaporate the flux in the solder, but then make contact with the bike cable end. this will increase the contact area with the bike cable therefor decreased the time it takes to heat it to the proper temperature. Then touch the other side of the cable with the flux core solder until it melts and the capillary action sucks the solder into wire. I set my iron to 850 degrees F.