Millin' the head and runnin' hot and compression

[dieselsmith]

I have a stock '99 shee, I want to mill the head down. How much can I take off of it? I am all of the sudden running hot, barfing out on the right pipe from the overflow tube. Could my antifreeze be bad? I topped it off with 60,000 mile Hyundai antifreeze after I changed the clutch cover o-ring. What is the wear limit for a top end compression wise? I am just under 120psi in both cylynders and how much variance can be between the two? Thanks for the help, i'm new here!

[samc]

try running engine ice, stuff works good cools your bike down fast

[shee rips]

sounds to me like your compression is still fine. If it gets to 100 i'd say its rebuild time.

i milled my head .020 and i had around 145 psi before the top end was broken in. im not sure what it has now.

milling it .020 put the squish at around .035.

im not sure what the limit for squish is, but i dont think i would want to go less than around.030

someone else could give you better info on this than me but shaving the head is a good cheap mod :thumbsup:

[Bansh-eman]

anti freeze is not a coolant, it has a slight cooling capability how ever its purpose is to keep the fluid from freezing in the winter.

 

you should drain your system and run either distilled water and water wetter or engine ice as a coolant. also look at getting a billet water pump impeller if you havent got one already.

 

120 psi is fine. as long as your within 10 lbs on each cylinder your fine.

 

as far as cutting your head goes it depends on what your trying to accomplish. if your just wanting more compression and still able t run pump gas you "should" be ok with 20 thousandths. the only 100% for sure way to know if your safe though is a compression test.

[blowit]

I have a stock '99 shee, I want to mill the head down. How much can I take off of it? I am all of the sudden running hot, barfing out on the right pipe from the overflow tube. Could my antifreeze be bad? I topped it off with 60,000 mile Hyundai antifreeze after I changed the clutch cover o-ring. What is the wear limit for a top end compression wise? I am just under 120psi in both cylynders and how much variance can be between the two? Thanks for the help, i'm new here!

 

 

Sounds like you might want the check your impeller. The OEM piece is plastic and failures are common. Antifreeze offers no benefit in cooling capacity but rather increases boil over and freeze protection. There are additives that have more exothermic value like water wetter that can help in cooling but sounds like you have a mechanical problem.

 

Also note that if you topped of the overflow bottle and suddenly it vents on the pipe, this is completely normal. As long as the bottle maintains some fluid in it, you are fine. We always route that hose under the bike so it does not make a mess on the pipes.

 

 

Brandon

Edited August 16, 2007 by blowit

[ksalvitelli]

I have a stock '99 shee, I want to mill the head down. How much can I take off of it? I am all of the sudden running hot, barfing out on the right pipe from the overflow tube. Could my antifreeze be bad? I topped it off with 60,000 mile Hyundai antifreeze after I changed the clutch cover o-ring. What is the wear limit for a top end compression wise? I am just under 120psi in both cylynders and how much variance can be between the two? Thanks for the help, i'm new here!

 

I will bet you the price of a head gasket.................you've blown one. Banshees don't barf unless compression is filling up the radiator. Before you go out and do all the 'coolant tricks', pull the head off and take a look at the head gasket. It will be obvious if it is blown. You will see an area missing black gasket material between the cylinder and water jacket on the intake side of the cylinder. It will most likely be the left cylinder that is blown if not both.

 

Milled head without bigger jetting = too lean and blow head gasket.

 

You state that you haven't milled the head yet and your compression is 120psi. If this is true then you need to find out why you are not getting enough fuel to the pistons. I have never seen a completely stock Banshee.............overheat. They are 'bullet proof'.

Edited August 29, 2007 by ksalvitelli

[J-Madd]

I will bet you the price of a head gasket.................you've blown one. Banshees don't barf unless compression is filling up the radiator. Before you go out and do all the 'coolant tricks', pull the head off and take a look at the head gasket. It will be obvious if it is blown. You will see an area missing black gasket material between the cylinder and water jacket on the intake side of the cylinder. It will most likely be the left cylinder that is blown if not both.

 

Milled head without bigger jetting = too lean and blow head gasket.

 

You state that you haven't milled the head yet and your compression is 120psi. If this is true then you need to find out why you are not getting enough fuel to the pistons. I have never seen a completely stock Banshee.............overheat. They are 'bullet proof'.

 

 

I'm sorry but I have to disagree....although I do agree that Banshees almost never overheat unless they've made several passes in a row drag racing, climbing hills,or are extremely lean.

 

If the head gasket was leaking, coolant would leak into the cylinder, putting out the spark.

[ksalvitelli]

I'm sorry but I have to disagree....although I do agree that Banshees almost never overheat unless they've made several passes in a row drag racing, climbing hills,or are extremely lean.

 

If the head gasket was leaking, coolant would leak into the cylinder, putting out the spark.

 

 

The gasket is leaking only when extreme demands are placed on the engine. If you checked the compression it would read normal. Like I said, I will bet you a new head gasket. You won't get to the point that it leaks so bad coolant just runs into the cylinder. As it gets worse it will spew anytime the bike is running hot or cold. After that if you are still trying to ride it around, it will put a dime size hole right through the piston when the dam finally breaks.

 

Leaky head gaskets on stock milled heads is quite common. People always think they have cooling issues. Nope, head gasket is burnt through from a hot spot that forms at the intake side of the piston. Need more fuel baby!