have the opportunity to buy a 99 yzf400 after looking at a klf 300 with rattly engine and hole in the crank case so leaking oil and I walked away from it. YZF has supposed rebuild 25 hrs ago, with receipts, looking at about $1800 NZD, ($1500 USD). Any real / common probs with this bike? Is maintenance a real money pit with these bikes, i will be doing some trail / forest riding about 2 times a month only, and am 41 yrs, so not into racing etc. I am new to yamaha after riding Hondas most my life in the old days.