Snopczynski Posted May 4, 2007 Report Posted May 4, 2007 If I am all stock motor now with 20cc domes and its 155psi comp, what will my comp. go to after just being ported with the 20cc domes? I want it to be at 165-170 psi range with my port work. Quote
CRAZY-SHEE! Posted May 4, 2007 Report Posted May 4, 2007 (edited) well, if ur looking for 175 psi ur talking racing fuel, and honestly racing fuel in just a ported motor is a waste. just not worth it. get some pipes, carbs, reeds, etc and then maybe it would be worth it.. most people only run racing fuel in stock banshees if theyre actually racing it and need to squize every bit of HP out of it.. that and most people run race in a cub. as far as raising the comp, i dont know.. i think port work can actually lower it sometimes. Not sure though.. Edited May 4, 2007 by CRAZY-SHEE! Quote
Bansh-eman Posted May 4, 2007 Report Posted May 4, 2007 (edited) when you port it ... your compression should drop a couple of lbs... 3 or 4 maybe, depends how agressive th porting is Edited May 4, 2007 by Bansh-eman Quote
06BaNsHeE Posted May 4, 2007 Report Posted May 4, 2007 well, if ur looking for 175 psi ur talking racing fuel, and honestly racing fuel in just a ported motor is a waste. just not worth it. get some pipes, carbs, reeds, etc and then maybe it would be worth it.. most people only run racing fuel in stock banshees if theyre actually racing it and need to squize every bit of HP out of it.. that and most people run race in a cub. as far as raising the comp, i dont know.. i think port work can actually lower it sometimes. Not sure though.. Running race gas will actually hurt your hp if you dont need it.I was told you can run av gas up to about 170-175psi.Porting it will lower it.get some 19cc domes and youll be around 175.And if your porting it and dont have pipes well get pipes first.Dont run a ported bike with stock pipes. Quote
Snopczynski Posted May 4, 2007 Author Report Posted May 4, 2007 I alreay have all the bolt on stuff, I just need porting and pistons. I want to run it at 165-170 range so I can stick with 92 octane pump gas. Quote
06BaNsHeE Posted May 4, 2007 Report Posted May 4, 2007 I alreay have all the bolt on stuff, I just need porting and pistons. I want to run it at 165-170 range so I can stick with 92 octane pump gas. 170+pump gas=BOOM Quote
Snopczynski Posted May 4, 2007 Author Report Posted May 4, 2007 170+pump gas=BOOM According to my motor guy that has done all my previous drag stuff 170+pump gas= ok! I used to run 165 psi in my drag bike on 92 octane pump gas. Quote
CRAZY-SHEE! Posted May 4, 2007 Report Posted May 4, 2007 (edited) thats not good for it dude :shoothead: u should run race gas in it.. also for the bolt on stuff, i was thinking all stock, not bolt ons.. big diff. Its totally cool if u have all the bolt ons.. port it, check ur comp, if its a 175, u gotta run some 110 in that biotch. Edited May 4, 2007 by CRAZY-SHEE! Quote
blowit Posted May 4, 2007 Report Posted May 4, 2007 thats not good for it dude :shoothead: u should run race gas in it.. also for the bolt on stuff, i was thinking all stock, not bolt ons.. big diff. Its totally cool if u have all the bolt ons.. port it, check ur comp, if its a 175, u gotta run some 110 in that biotch. We have never experienced detonation on the dyno while using 20cc domes on stock porting. 175lbs is absolutely in the window for pump fuels. Depending on what type of porting you are looking at, your comp can drop by as much as 20lbs. Any engine builder that knows how to make real power will want head mods to match the porting. This is because of the drastic pressure drop. Domes are very relative to elevation. You may need 18cc domes just to run pump fuels properly at higher elevations with your porting. Brandon Quote
06BaNsHeE Posted May 4, 2007 Report Posted May 4, 2007 (edited) w/e floats your boat I guess.I sure as hell would ATLEAST run straight av gas or 50/50 av race gas but that would be pretty stupid.Hope it dont go beeppp beeeep beeep BOOM.I learned my leason the hard way Edited May 4, 2007 by 06BaNsHeE Quote
CRAZY-SHEE! Posted May 4, 2007 Report Posted May 4, 2007 w/e floats your boat I guess.I sure as hell would ATLEAST run straight av gas or 50/50 av race gas but that would be pretty stupid.Hope it dont go beeppp beeeep beeep BOOM.I learned my leason the hard way :shoothead: < urs and his motor. Quote
Snopczynski Posted May 4, 2007 Author Report Posted May 4, 2007 OK, I guess the fact that both my old motors, both my cousins motors, my uncles motor, and my brother in laws motor all have 165-170 psi comp on pump gas doesn't mean anything. I do know that my comp. will change with porting, and I know it pretty much depends on exhaust port timing. I was just checking to see if you guys had any knowledge as to how much change it may be. I am aware I will probably have to buy new domes though. Quote
CRAZY-SHEE! Posted May 4, 2007 Report Posted May 4, 2007 depending on the porter.. anywhere from 5-30 psi. Quote
shee rips Posted May 4, 2007 Report Posted May 4, 2007 my yz 125 is ported and has head work done to it. Im not sure who it was done by because the guy before me did it. the bike only reads 100 psi on my guage. thats with a fresh top end too. the bike rips so I figured it was my guage, but if porting lowers your comp that makes sense. I tested it before and after a rebuild and there was no change, still 100 psi. I noticed a power increase after but...probably my guage not working right. :shrug: Quote
Bansh-eman Posted May 4, 2007 Report Posted May 4, 2007 unless your going for a full drag port your only going to drop a few lbs... the more metal the more lbs... what kind of port you looking at getting? Quote
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