Bubba,Talonhawk or someone .

I am going to get the head milled on my TB. How much should I go, what gains should I expect, Do I have to use a higher octane fuel, What else should I expect? I hear this is a great thing to do with a ported cylinder.

 

I don't know how much HPD milled mine but it did look alot different
when I got it all back. The other things that I had to do was to use
race gas, at least 108 octane and go to a BR9ES spark plug. I'm getting
ready to pull the flywheel off and remove the starter. I'm going to have
HPD lighten the flywheel about 1 1/2 lbs.

 

I had the head milled on myn, They took 0.030 off and I gained 20PSI of compression I'm now running about 140psi on 93 premium and no signs of pre ignition or detination ping. Have you considered having a thinner copper gasket made? it would be cheaper and you would gain the same. The first day I put my motor together It blew a head gasket "Cometic" I don't reccomend them I run Versarah with no problems. I get terrible fuel milege I don't know if milling the head takes it away. You will gain a lot of torque and bottom-end it's like a 4 stroke now. I would do it it's worth a couple of ponies
TalonHawk, How far are you from the Badlands in Indiana and have you ever been there I'm going this summer it sounds like a cool place from the stories I heard

 

I did that on my first 250. I made a soft copper thinner head gasket . Not many people know this, but it is the same as a Honda 250R head gasket. I wouldnt go too much. I would call Rick Ritter. Seems to me that they do other machining besides just milling it. Never had a stock one done,though. Bubba

 

So if I got a 250r head gasket that would be almost the same?

Mojave300ex

I used to live in illinois and went to badlands a couple of times a year for mudbog compitition. It is a real cool place. Lots of places to ride.

p.s This 250 is getting really fast with all the work so far. I CANT STOP NOW!!! I did 3 consistant runs today at 66mph. Not bad huh?

 

The only thing I cant tell you is how thick the Polaris gasket is in comparison. My buddy had his Honda apart at the same time my Polaris was down. Dont know how it happened, but we found out that they were the same. Seriously I would do some checking to see if they just mill it or actually do some machining. 66mph out of the 250 is flying high![img]i/expressions/face-icon-small-happy.gif[/img]

 

And still climbing.

My compression is about 130psi. Should I make a copper gasket and then recheck the compression to see if I gained any at all. If I do gain some, how much is to much?

 

If you get a thin gasket you have to have a minumum of 0.034 squish band clearence for rod stretch under higher RPM, this includes the thickness of the head gasket. To measure you get a caliper and measure the distance between the flat gasket surface of the head and the bottom lip of the dome. I had an experience when I raced MX on my YZ80 we milled the head and I was wide open and the piston slapped the surface of the head and runied the motor/head.

 

I milled my head .020 off it with no problems. I have mine pretty much as far as I can take it right now an it gose really good. The biggest help is the loss of weight. Now just have to wait for the season to start agine an put it in to action.

 

mojave300ex
I live in central Ohio. I'm not sure how far that is to the badlands but I'll try to
talk my brother into coming out this summer (he has the truck)[img]i/expressions/face-icon-small-smile.gif[/img]