My XBR has an XL600 barrel and piston,and the compression ratio is quite high. A Motobatt battery will start the bike from cold,usually,but it only turns over a few times before giving up. Luckily,the bike starts easily (thank you,Honda,for the decompressor),otherwise it would be a real pain. I have once bump started it in third down a long hill,but it usually locks the rear wheel. I'm quite happy with the Motobatt,nothing else seemed to work.