I'll share the info I have .
All models KLX 250 and 300 from 93 to the latest model share the same cam timing.
Inlet Open 22º BTDC
Close 62º ATDC
Exhaust Open 61º
The KLX250 D1,D2,D3,D4
bikes were the most powerful for the engine size (only 1 hp less powerful than the KLX300 A2.)
KLX250 D1-4. (non US model) 32 HP @ 8500rpm
(US model) 30.5 HP @ 8500rpm.
Ignition timing: 5º BDTC @ 1700rpm to 40º BTDC @ 3000rpm
Dry Weight 104 KG.
KLX250 E1, E2, E3. bikes were heavier (rack large glass headlight etc.) and pretty much what we get today.
KLX250 E1-3. AUS spec 25 HP @ 8000rpm.
Ignition timing: 5º BTDC @ 1300rpm to 35º BTDC @ 5000 rpm.
(This is the ignition the I have on my 07 KLX250RH7 AUS spec bike, OE. Seems it can be traced back all the way to 94 with the E model bikes.)
KLX250S (09 and on.) AUS spec 23 HP @ 8500rpm (US spec) 15 HP @ 8000rpm.
Ignition timing: (US spec) 10º BTDC @ 1300rpm to 25º BTDC @5000 rpm. (AUS spec) BTDC 10º @ 1300rpm to 35º BTDC @ 5000rpm.
KLX300 A2. (AUS spec) 33 HP @ 8500rpm (US spec) 26 HP @ 7000rpm.
Ignition timing: 10º BTDC @ 1700rpm to 40º BTDC @ 3000rpm
There are differences in power and ignition as I've displayed. Interesting to note that the KLX300 A2 has 40º of advance from only 3000rpm and the KLX250 D series bikes have the same maximum advance from the same rpm. The D series bikes make just 1 hp less than the 300 A2 bike despite having 50cc less.
Makes me think that when I finally fit up the Kawa' 300 kit I have sitting in the garage I could possible be on my way to 30 HP, given the max advance I'm working with (35º) is close to that of the D series 250cc and A2 300cc bikes.
Although 40º advance from 3000rpm sounds like the way to big HP from these bikes. Pity it's not a viable mod as the charging systems are AC vs DC.