mopar1rules
Active member
My 98 srx 600 has a bender can, boysen dual stage reeds (just petals), Hauck boost bottle, air box with only the vertical dividers in the bottom removed, and stock clutching. I jetted accordingly and it ran awsome. This year I got greedy and had the Hauck head mod done. they shaved the heads redomed them and gave me a thicker base gasket. I also asked about the piston hole 'cause i know they do a mod to it with the v-max 4's. the guy said i could drill it out with a 1/2 inch drill, so i did at a buddies work on a cnc. Now it's all together and running, VERY lean, i positivly have no air leaks any where, every thing has new gaskets and torqed according to the book, coolant has been bled, and power valves i cleaned and set up. so far i went up 2 main jet sizes and 1 pilot. the pilots came around but i might go up one more, the mains were like i didnt even do anything. I have 130 lbs of compression on all 3, which is what Hauck said it should be. So do i have to just rejet big time? Also, my friend with an '03 rev 600 put on only a billet head this year too. He had to go up 9 main jet sizes to get the plug color card board looking. What gives? Is this normal? Any thoughts more than welcome.
Well you have changed everything with the engine now, the thicker base gasket changes the port timing, the heads being cut adds a small amount of compression back to the engine. When you raise the entire cylinder you raise ALL the ports and raising the exh. port lowers the compression. You also added deck clearance to the motr and this changes how the turbulence in the ehad works. Drilling the hole in the piston was a bad move as the hole should be offset towards the top of the piston, not below the original hole and just driling it out you took material away from the floor of the hole and changed the timing of the rear boost port there as well. With all the other add ons its very likely you may end up several, or many jet sizes up to get into the correct mixture, how far only you will know with your combo of parts and mods added on. Easiest thing to do is work on the carbs 1 circuit at a time, pilot jets and fuel screws, will controll the intial loading of motor launch and slow speed, the needles and overlap of the pilot jet will controll your midrange cruising, and lastly the main will controll the fuel flow at 3/4-wide open throttle. Do each step checking plug color and piston wash and tune from there.
mopar1rules
Active member
Thanks for the info Mrviper, you sure know your stuff!!! I'll have to call Hauck again and see what they claim the advantage of the drilled piston port is. Also do you think i'm losing any power with my pistons being drilled like that? If so do you think it would be worth my time and money to put brand new pistons in? They claim a 5-8 horse gain midrange and 3-4 horse gain on top end on just the head mod. Thanks again for the help!!!!
mopar1rules
Active member
Can anyone help out to with my rev? I had to go up one more with the mains (10 sizes up from stock) and shim the needles an additional .020". Does that seem right?