BakoBanshee Posted April 30, 2015 Report Share Posted April 30, 2015 I'm gonna freshen up the top end and wanted to know what is the max compression in psi that I can safely run on 91-octane pump gas at sea level? How much shaved off the stock head would achieve this max psi? What size domes would this be if I were to go the cool head route? Does a cool head help in keeping the temps down, or is it more for flexibilty in changing domes for compression for different fuels/mods? Thank! Quote Link to comment Share on other sites More sharing options...
camp0429 Posted May 1, 2015 Report Share Posted May 1, 2015 .030" milled should put you around 150ish. Did on mine anyway Quote Link to comment Share on other sites More sharing options...
Phelps Posted May 1, 2015 Report Share Posted May 1, 2015 just buy an aftermarket head from a sponsor and have them set you up with the proper domes. milling a stock head for compression does nothing for performance only hurts it. Quote Link to comment Share on other sites More sharing options...
BANSHEE HP Posted May 1, 2015 Report Share Posted May 1, 2015 I just tore down a bike that had a milled stock head... .030" squish and 150psi. Wrong way to do it as Phelps said. Quote Link to comment Share on other sites More sharing options...
67banshee01 Posted May 3, 2015 Report Share Posted May 3, 2015 (edited) I've ran nothing but a stock head. The first one was stock, the second I had milled 30 and now the one I have now is my original set up to run my 4 mil crank. Reliable and no worries about I ring seals. Plus you can't tell its packing a lil more heat than it looks.( also noticeable difference fr milled to having the head milled) Edited May 3, 2015 by 67banshee01 Quote Link to comment Share on other sites More sharing options...
mopar1rules Posted May 4, 2015 Report Share Posted May 4, 2015 Agreed....i ran a stock head that i milled .030" off on my stock stroke setup and i run on a stock head on my 4mil too. It's cut for the additional stroke of course. I love how it never leaks like my "poor design" cool head did. Don't know why people don't like the stock head. Just because its a stock part, doesn't make it bad. And just because a part is aftermarket, doesn't make it good or better than a OEM part. To the original poster, you could have your stock head cut for cheap and pick up some power. Quote Link to comment Share on other sites More sharing options...
Rigid_Banshee Posted May 4, 2015 Report Share Posted May 4, 2015 Apparently the stock heads cause overheating at high revs but ive had no problems using them at all I actaully prefer stock and the metal gasket instead of sorting out o-rings. Only advantage is a coolhead can switch out its domes and is made of almunium Quote Link to comment Share on other sites More sharing options...
blowit Posted May 5, 2015 Report Share Posted May 5, 2015 Just to clarify, factory heads do not cause overheating and any such claims cannot be met with any credible or quantitative data to support the claim. In our experience in cutting the OEM Banshee heads for the last decade or more, the cut or dimensions make big difference in how much heat transfers to the engine and how much goes into the exhaust. Factory Banshee heads are all Aluminum. It should be worth noting that Yamaha deleted the primary cooling passage and primary source of heat!.... The exhaust port! They stuck a plug in the bottom and called it a day! We never did commercially offer "just a trim" on the stock heads for a reason. If you are going to take the time and effort to cut the factory head, please do it right and improve it while you are there. I don't believe we ever had a call to say our head work did nothing to improve performance. However, we have never just "shaved" a head for a customer so that might not be a good comparison. Brandon Mull Engineering Quote Link to comment Share on other sites More sharing options...
registered user Posted May 5, 2015 Report Share Posted May 5, 2015 im not one bit impressed with coolhead. using oem head here Quote Link to comment Share on other sites More sharing options...
trickedcarbine Posted May 5, 2015 Report Share Posted May 5, 2015 im not one bit impressed with coolhead. using oem head hereHave you investigated girdle options? Like the TDR one that is solid aluminum? Quote Link to comment Share on other sites More sharing options...
BANSHEE HP Posted May 5, 2015 Report Share Posted May 5, 2015 There's quite a few "cool-heads" that either route the water wrong or just plain don't hold as much water. Quote Link to comment Share on other sites More sharing options...
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