I can't help you with 650 specifics, but I can perhaps give you the oids to help you find it. Do you have the mibs installed? If so, walk JUNIPER-MIB::jnxOperatingTable and see if any of them fit.
snmpwalk -v2c -c @readonly 10.10.1.1 JUNIPER-MIB::jnxOperatingTable
If not, that corresponds to oid .1.3.6.1.4.1.2636.3.1.13, but you may have trouble deciphering what's what. Here's what I get for descriptions and corresponding CPU util:
SNMPv2-SMI::enterprises.2636.3.1.13.1.5.1.1.0.0 = STRING: "midplane"
SNMPv2-SMI::enterprises.2636.3.1.13.1.5.2.1.0.0 = STRING: "PEM 0"
SNMPv2-SMI::enterprises.2636.3.1.13.1.5.7.1.0.0 = STRING: "FPC: FPC @ 0/*/*"
SNMPv2-SMI::enterprises.2636.3.1.13.1.5.8.1.1.0 = STRING: "PIC: 8x FE Base PIC @ 0/0/*"
SNMPv2-SMI::enterprises.2636.3.1.13.1.5.9.1.0.0 = STRING: "Routing Engine"
SNMPv2-SMI::enterprises.2636.3.1.13.1.5.9.1.1.0 = STRING: "USB Hub"
SNMPv2-SMI::enterprises.2636.3.1.13.1.8.1.1.0.0 = Gauge32: 0
SNMPv2-SMI::enterprises.2636.3.1.13.1.8.2.1.0.0 = Gauge32: 0
SNMPv2-SMI::enterprises.2636.3.1.13.1.8.7.1.0.0 = Gauge32: 0
SNMPv2-SMI::enterprises.2636.3.1.13.1.8.8.1.1.0 = Gauge32: 0
SNMPv2-SMI::enterprises.2636.3.1.13.1.8.9.1.0.0 = Gauge32: 20
SNMPv2-SMI::enterprises.2636.3.1.13.1.8.9.1.1.0 = Gauge32: 0
If you're not familiar with the way it indexes, it does so off of the last four digits, so '9100' refers to my routing engine, and then each OID ending in 9100 is a stat of that routing engine. So maybe your routing engine just has a different index. Memory is the same:
SNMPv2-SMI::enterprises.2636.3.1.13.1.11.9.1.0.0 = Gauge32: 60
and temperature:
SNMPv2-SMI::enterprises.2636.3.1.13.1.7.9.1.0.0 = Gauge32: 49
I'd recommend installing or at least reading the mib files because they'll give you info on what the values mean, what units they're in, etc.