dt1 250 69.  it seems like people say manuel says 15 psi for rear.  it just seems really low to me.  ill be on the street first with dunlop tires.  some people said 25 psi in search.  what to do?  thanks for help

It's a lightweight, relatively low speed vehicle.  

From the actual owner's manual:

Try 15- then 20 and 25. If you are a bigger, husky person, 15 might not do as good.
A lot of road, keep pressure a bit higher.

I like the low tire pressure mainly because most of my tires are way beyond their safe life span and the rubber is hard and dry. I simply cannot keep up with tire replacements. I tried replacing one a month but have fallen behind that target. At one tire a month it will take me 2.5 years to resole the entire herd…  I am now targeting the larger displacement bikes since they see higher speeds than the little guys that are simply ridden around my own property.

The stock "trials" tread pattern seems to get squirrelly at higher psi IMHO.  And the ride gets harsher.  

I don't ride on the highway much, but when I take a paved ride for a distance at higher speeds (55+ mph) I may run 18/21, especially if I've loaded the bike and myself down with water, tools, and spares.  Around town, stock pressures work great.  

 

'72 DT2, I run what the manual states as Front 13psi, Rear 16psi. My riding this bike is primarily on the road with OEM style tires and it feels fine with my 155 pound body weight.

In my CT-1 / AT-1 service manual it says tire pressure is rider's choice, but for on-road they suggest 14 and 17. If running much lower, put locks on. I could swear I read in this forum several years ago that Yamaha later updated that, and said to run higher pressures on the road, but maybe I was imagining things. I only ride on the road, and I've been running 22 and 25 on Shinkos. When I was running 14 and 17 it seemed mushy, especially in turns. I weigh 180. Shinkos are rated max 32 psi cold.

I run 16 front 18 rear on all the Enduro's. I'm 6'2" 230 lbs. Works fine for me.