250r Head Milling?

[BigRedRunner]

Sorry for all the questions lately... 1985 250r 1.5mm over that will be running a rad valve and ESR pipe, whats a good amount to shave off the head? I will be running the genuine Honda gaskets for the ATC (medium thickness head gasket). I'll probably run this thing on 89 or more like 91 octane fuel (that's all the better we get around here). I've heard .010 off is the norm. I don't want to run the slightest of pinging.

[Dammit!]

I don't want to run the slightest of pinging.

Then don't mill it at all.

[BigRedRunner]

Well, within reason mind you. I did my truck at 9.3:1 and was aware that I had to run premium gas.

[Dammit!]

If you want more compression just use a CR250 head gasket. Cheaper and easier to un-do.

[sblt500r]

if you just have it kissed to clean up the head for flatness then run a the thinner gasket. then if it pinges you can just put the thicker gasket on and not have to change the head.

[Blown 331]

Yeah, just run the CR gasket or just one thin layer from a stock gasket, that's what I did and it does fine on 93. Off subject but you should be able to run 87 octain in a truck with 9.3 to 1 compression with out any problems at all. Most vehicles now days have more compressoin than that stock and run find on 87. Hell my mustang has 9.5 to 1 with 14 pounds of boost and I run 93 in that.

[86250RZ]

If you look in your owners manual you will see that Honda recommends 93 octain in a bone stock 85/86 250R and since you have access to fuel no higher than 91 octain I would advise you to leave the head alone.