So have a 2006 GS500, initially installed 1/4" fuel lines but they were almost impossible on the petcock side, changed to to 5/16" but now the shorter line on the tank side is not staying.

Is there any trick to it? Planning to use a ring type clamp on both lines and then tighten it up so that it stays there.

Appreciate any other thoughts? 

The OEM lines are different dimensions on either end. I had all kinds of problems until I learned this and order the OEM lines -- then no more problems.

+1 OEM

The OEM lines are not cheap but they are well worth it, not only are they different sizes on each end but they are properly flared and bent plus the outside diameters are designed to be thick but still sit side by side on the tank petcock. After you've taken the tank off a half dozen times you'll be glad you ponied up for them. They pay for themselves over the years.

I'm another (strong) vote for OEM lines and clamps.

Thank you all, OEM lines it is

$50 at partzilla before shipping for my '89. Prob buy, thanks for a good short string. Currently I have long lengths of clear yellowed urethane.

On the OEM line, do people cut then and insert aftermarket filters? Maybe only on the one from petcock to carb T?

no neccessary, theres one filter in tank, here has been discussion bout it and many were against the idea, guess it reduces fuel flow etc.. not really need to have two filters.

btw, guess i have those 1/4 fuel lines, were really a PITA to get em on, had to blow torch the ends, and now i just hope that i dont need to take the tank off, atleast theyre TIGHT FIT, no need to clamp them 

For the past two years I've been using 1/4" (6.4mm) ID fuel lines. The brand is "Continental" (made in USA) and although it is reinforced, it's still stretchy enough to fit the 8mm connections without using heat or too much effort. Just as well, because there is no chance of getting OEM parts locally here where I live. And importing is out of the question due to high cost.

I use something from the local bike junkyard - they say its tygon but no idea what it is. It seems to craze and crack if too much sun exposure, but fuel, no problem.
Cool.
Buddha.

I went to partzilla and tried to order OEM, they substitute one for another as sold out so no longer available. No go on that $60 order, keep my long wiggly OK looking tygons with strong clamps.

Too long and the loose generic hoses can crimp when stuffed in there, be sure of the lengths.