What hose works for the oil tank breather or over flow up by the cap? Mine is all hard and cracking. Looks to be pretty small diameter.

i have used several different types, but in the end found the original yamaha hose that I got on Partzilla the best.  Especially for the smaller pump to engine hose which seems to be the only type that has the proper dimensions and toughness to work with the little clamps, which are also quite good,  Old is sometimes good, I keep telling myself! 

I think that the overflow/breather hose has superseded to a dodgy yellow hose!

Yambits in the UK do a repro for some of the RDs, although I've found it too narrow. In the end I think that I used some new battery breather hose that I had lying around.

I stand corrected, you are right about the yellow one
but I did use a black yamaha hose on my overflow of DT360 and DT1E, I think I ordered several of these pump output hoses cause they were cheap and to my suprise pretty long too

www.partzilla.com/product/yamaha/90445-0...2e567c038f38bdfbb67f
 

Yes, with a number of Yamaha parts now, you get a fixed length and cut to what you need.

Often there is enough for two!

Nothing like carbon black to improve toughness 

I replace the breather hose and oil pump hose on my 75 DT250. I bought both from www.rockymountainatvmc.com. There shipping is the best I have found on-line.

HOLY CRAP
this place has many parts for my DT360A that partzilla didnt have....pistons, cranks, etc.
definitely going to buy from Rocky Mountain once I get my mits on my next project.