MILO Posted May 4, 2006 Report Share Posted May 4, 2006 stock bore -cylinders honed, wiseco pro lites, noss head w/20cc domes, v3's (all new and just installed) also new plugs, of course. no timing advance or porting, elevation about 1200 ft compression is reading about 137-138 on both sides. i thought it would be more in the 150's range i did the heat cycle deal like this: shee fired up right away, let it idle for not quite 5 minutes, and let cool. fired up and let idle/low throttle blips for about another 5 minutes and let cool. fired up and rode for a few minutes, let cool. fired up and rode for about 20 min, let cool. checked compression and got around 135. rode until well warmed up/hot, and checked again. about 137-138 on both sides with throttle fully open, and several reads. shee definitely has more snap and seems to have awesome throttle response, but i thought the compression would read higher. is there something i'm missing here?? Quote Link to comment Share on other sites More sharing options...
K5Banshee Posted May 4, 2006 Report Share Posted May 4, 2006 What elevation are you at??? http://www.nossmachine.com/banshee_heads.htm Maybe your compression tester is not 100% accurate? Quote Link to comment Share on other sites More sharing options...
MILO Posted May 4, 2006 Author Report Share Posted May 4, 2006 What elevation are you at??? http://www.nossmachine.com/banshee_heads.htm Maybe your compression tester is not 100% accurate? 511669[/snapback] about 1200 ft the chart on Noss's site is what i was going by and hoping to achieve. it's a new tester (actron) i had a thread in product reviews and the majority seemed to approve of it it's the first time being used. Quote Link to comment Share on other sites More sharing options...
dlnoss Posted May 4, 2006 Report Share Posted May 4, 2006 Does the compression tester thread into the spark plug hole the same depth as a spark plug? Some of them have short threads which will give you a false (low)reading because they displace less volume in the dome. Quote Link to comment Share on other sites More sharing options...
2bzy2p Posted May 4, 2006 Report Share Posted May 4, 2006 that sounds about right for the compression with those domes stocks about 120 Quote Link to comment Share on other sites More sharing options...
MILO Posted May 4, 2006 Author Report Share Posted May 4, 2006 Does the compression tester thread into the spark plug hole the same depth as a spark plug? Some of them have short threads which will give you a false (low)reading because they displace less volume in the dome. 511685[/snapback] well that makes sense to me. i didn't realize that's what one of the adaptor's was for. the one i used was really short. i found an adapter in the kit that is very close to the length of the plug. i'll give it another shot tomorrow. thanks bud Quote Link to comment Share on other sites More sharing options...
dawarriorman Posted May 4, 2006 Report Share Posted May 4, 2006 Yeah Im at 500 ft (not too much lower) and I pulled 153 on a fresh top end with 21 cc domes. The adapter does sound like your problem though. Quote Link to comment Share on other sites More sharing options...
Ducman Posted May 4, 2006 Report Share Posted May 4, 2006 Does the compression tester thread into the spark plug hole the same depth as a spark plug? Some of them have short threads which will give you a false (low)reading because they displace less volume in the dome. 511685[/snapback] Hmmm, I bet I've been reading #'s a bit lower than they really are. Darn, I need a new tester now. Quote Link to comment Share on other sites More sharing options...
MILO Posted May 4, 2006 Author Report Share Posted May 4, 2006 Hmmm, I bet I've been reading #'s a bit lower than they really are. Darn, I need a new tester now. 511756[/snapback] you gotta love the HQ for info, but one way or another, it's always got ya spending more $$ Quote Link to comment Share on other sites More sharing options...
Ducman Posted May 4, 2006 Report Share Posted May 4, 2006 MILO, have you measured your squish? I have had Noss cut custom domes for me twice now because the ones that were installed when my motor was built had too much or not enough squish pluss to big or too little domes to get the psi I was looking for. Both times it has ran waaaay better with the custom domes that get the squish and psi to optimum specs pluss custom dome design. Most noticeable in the bottom end to midrange power, but I'm sure it improved all the way through the power range. Off the shelf domes are usually made with a little safety factor built in to the squish so it ends up a lot bigger than what is optimum. Also the cylinder base gaskets you use can change your squish up to maybe as much as .020" depening if you use stock .030" or some of the the thinner aftermarket ones, closer to .010". If you measure your squish an you are .070" and get domes cut so you are .035" then you couldl probably gain about 10 -15 psi which would get you to the 150 psi you were looking for. If your squish is big enough it could be adding a couple extra cc to each dome so it would be like running 22cc domes. There are also other more complex things included in dome design, but the squish tollerance is a big part. Cylinder volume = Pi(Radius^2)height Example Squish (height).035" = .0889cm Diameter = 66mm = 6.6cm = 3.3cm Radius 3.14(3.3^2).0889 = 3cc So having squish at .070" adds 3cc per dome over a squish that measures .035" given the same dome shape/ size but adding .035" of squish Quote Link to comment Share on other sites More sharing options...
mouse Posted May 4, 2006 Report Share Posted May 4, 2006 i just had my moter redone and put the 21 in and had 120 psi switched it to 19 domes and have 176psi and running 110 octain. im also at 1100 evlevation Quote Link to comment Share on other sites More sharing options...
MILO Posted May 5, 2006 Author Report Share Posted May 5, 2006 MILO, have you measured your squish? I have had Noss cut custom domes for me twice now because the ones that were installed when my motor was built had too much or not enough squish pluss to big or too little domes to get the psi I was looking for. Both times it has ran waaaay better with the custom domes that get the squish and psi to optimum specs pluss custom dome design. Most noticeable in the bottom end to midrange power, but I'm sure it improved all the way through the power range. Off the shelf domes are usually made with a little safety factor built in to the squish so it ends up a lot bigger than what is optimum. Also the cylinder base gaskets you use can change your squish up to maybe as much as .020" depening if you use stock .030" or some of the the thinner aftermarket ones, closer to .010". If you measure your squish an you are .070" and get domes cut so you are .035" then you couldl probably gain about 10 -15 psi which would get you to the 150 psi you were looking for. If your squish is big enough it could be adding a couple extra cc to each dome so it would be like running 22cc domes. There are also other more complex things included in dome design, but the squish tollerance is a big part. Cylinder volume = Pi(Radius^2)height Example Squish (height).035" = .0889cm Diameter = 66mm = 6.6cm = 3.3cm Radius 3.14(3.3^2).0889 = 3cc So having squish at .070" adds 3cc per dome over a squish that measures .035" given the same dome shape/ size but adding .035" of squish 511962[/snapback] uhh, ok so how do you measure the squish?? the base gaskets i used are yamaha gaskets from the stealership, which i believe were in in the .030" range. i did put a tiny bit of sealer on them also for insurance, but just very thin. they were not the kind like what was on it, steel with a coating on them. by the way, i put in the long reach adaptor on the compression tester and got the same readings as before. i'm tempted to try a different tester, just out of curiousity. Quote Link to comment Share on other sites More sharing options...
Ducman Posted May 5, 2006 Report Share Posted May 5, 2006 To measure squish, remove the spark plug, take a long piece of electrical solder and put it through the plug hole untill it contacts the inside cylinder wall. Then turn the crank with your hand on the kickstart so the piston goes past TDC. The piston will smash the solder against the squish band of the dome. Then you can measure your squish. I always make sure to get the piston near the top of its stroke, and still moving upward before inserting the solder so I dont shear off the end of the solder in one of the ports. Also try to measure on either sides of the piston above the wrist pin so the piston doesn't try to tip away from the solder when it smashes it. Its easiest to do when the tank is off but not neccessary. Then take a set of dial callapers or a micrometer and measure the thickness of the smashed solder near the tip which should represent the squish at the outer edge of the dome. Most solder is .060" so if it doesn't show any smashed area at the end of the solder then your squish is bigger than .060" and you need a fatter piece of solder or twish a piece of the .060" around itself so you have about 4" of twisted solder. Once you have this measuremet you can either send noss your domes which is best so he can measure the domes actual cc's and specs, or just measure the lip on the underside of the dome on the outer edge. Once you know these 2 dimensions Noss can cut you a new dome that will result in .035" of squish and he can give you a little wider or narrower squish band depending on if your looking for more low end or top end performance and your new domes cc's shoud be a true 20cc when the piston is at TDC. Quote Link to comment Share on other sites More sharing options...
MILO Posted May 6, 2006 Author Report Share Posted May 6, 2006 ok, i understand your measurement technique, and thanks for the tip. wouldn't i be just as well off to just go with 19cc domes and see what happens? after retesting with another tester, that is. Quote Link to comment Share on other sites More sharing options...
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