At the risk of sounding thick... What octane is best?

[Monsterbishi]

What's this I hear about 'tuning' a bike to a certain type of fuel? If compression ratio is what determines what octane is best, what has tuning to to do with it?

The static compression ratio actually plays very little in what octane fuel to use, cam profiles aside, the ignition timing advance table is generally what needs to be adjusted when playing with higher octane fuels.(Or retuning to use crappy lower octane fuels for that matter as well)

Electronic Injected engines usually have self-adjustability within the ECU's program to accomodate for minor changes in octane.

[YellowDog]

Am a learner on my 1st bike, a 95 honda cbr 250rr. Should I run it on regular or 96, or that bp 98?

May be you just want to check with your local garage over any problem with higher octane they have experieced for your model/year. I have heard of some issues with older bikes over the leaded to unleaded thing, which can break the conventional rules.

[$CENSLS1$]

So what should I be running my '02 KLX250 on?I've always used 98 mainly because it has a relitivly high compression ratio of 11.1/1 i've heard?
It does seem to knock a bit at higher revs though but 95 feels worse right through the rev range..Any ideas?

[YellowDog]

The issue you mention may or may not be fuel related. Being quite a recent bike I am sure there are lots of Kwaka experts able to help you with adjustments to address such problems.