I don't have an owners manual. Can I just use any type of antifreeze in the bomb?

 

Silicates can wear away at the water pump seals. I would avoid automotive coolant. To be safe buy a pre-mix made for motorcycles such as Honda. http://faq.f650.com/MainIndex/CoolingSystem.htm

Are you flushing the cooling system or do you have a leak?

Be sure to "bleed" the air out of the system after re-filling or you will boil over first time out.