After loads of detective work I have managed to get some useful 250 info for the GJ74A bikes. These Japanese pages are a little strangely worded after translation BUT the information they contain is like gold dust!
Service info here http://translate.google.co.uk/translate?hl=en&sl=ja&u=http://www1.synapse.ne.jp/s-hara/bandit/ban-kisoa.html&ei=nEYXTNXQEcLQ4gbjn4TmCw&sa=X&oi=translate&ct=result&resnum=7&ved=0CD4Q7gEwBg&prev=/search%3Fq%3Dmikuni%2Bbdst30%26hl%3Den%26sa%3DG
Part Number information here http://translate.google.co.uk/translate?hl=en&sl=ja&u=http://www.bands.ne.jp/faq/faq-us-pr250.html&ei=-RUaTMaACZCK4ga7-KHQCg&sa=X&oi=translate&ct=result&resnum=2&ved=0CCAQ7gEwAQ&prev=/search%3Fq%3D%252213258-06C00%2522%26hl%3Den
I have been trying to find Carb float gaskets for AGES, now at least I have a part number :-) 13258-06C00
Pete