Has anyone ever had a stock 760 head milled to even up the compression on both cylinders? I would assume that you would mill out to match the biggest dome and then plane the head to bump the compression back up. I just want to find out if anyone has done this and how much to plane off ect. Im having trouble with my front cylinder running lean and the back running rich when tuned the same and dont want to go to staggered jetting cause it sounds like trouble.
I modified a standard 760 head. ... tho I do run staggered jetting (under advice of Roger, as mine is now in a blaster II... so much heavier than SJ) we had heaps of squish available ...and took off .8mm compression went too high for me (197) went about rectifying comppression back down... milling was a bit of an expensive hassle as the rear sparkplug hole was not true centre (so a tool had to be made).. may pay to check yours as this was on a standard yamaha 760 head - I do know someone with the tool if required. ...previously on my 760 superjet I had been running a 701 head which Roger had taken out to 760 and skimmed (now on "Garry's" SJ, if he hasn't changed it) which was a lot less hassle I think and ran 175 compression- I would have chosen to keep the 701 head but needed the rear exhaust mounts of the 760 head for the blasters pipe. hope info useful
Yes interesting thanks so if i wanted to mill a 701 head do I simply just get the domes widened and retain the same shape and angle of the dome or do people change the shape entirely? also how much do you have to plane of a 701 head once its been milled out (if any)? Has anyone done this themselves?The work is easy I just need hard facts to work to. P.S. Redtro thats a MASSIVE stab in your profile picture!
...my 701 head had .8 off it. - am pretty sure was kept same shape but taken out to 84.5mm ...yeah cheers, that blaster does big stabs...shame pic wasn't 3/4 a second later when fully inverted & ready for entry Rog suggested the staggered head and jets were to help against crank twist on the heavier hull... I also run alloy flywheel to further compensate
FYI... if can't be bothered with all that... staggered settings (allowing same turns out) on the blaster were: in my ski same pilots (120) mains 1 size bigger eg. front carb 135, back carb 137.5 I took both these up (125 pilots, fr 137.5, back 140) allowing for a riva pipe ...then both carbs ran same turns out no problem
I get all rogers heads done for him so if you send it to me i can do it, he usually takes 1mm off then machines it out to 84mm at a certain angle. When i did mine i didnt take anything off it just modified the bowl and it was at 175psi.
