Fastashell69 Posted October 24, 2006 Report Share Posted October 24, 2006 I was wondering what or how to guage the compression difference from altitude to altitude. I was recently at Sand Mountain Nevada and i checked my compression up there and it was 145-150 lbs what should it be in Santa Rosa California which is probably close if not sea level. and what is safe to run my compression to with out blowing up the motor. i heard to run it between 175 and 200 lbs with race gas would be just fine any suggestions. Quote Link to comment Share on other sites More sharing options...
Washburn Posted October 24, 2006 Report Share Posted October 24, 2006 The only way to be sure of your compression is to take a gauge with you and use the 14mm adapter the 18mm adapter is to big it will hit the top of your piston. From what I hear 165-170 is where you start having to use race gas probably 50/50. Ide check that Im not 100% on it. If I were at 200 I would definatly run straight 110 and get a new crank and get added welds or just get you stock crank trued and welded. 200lbs of compression is alot. Quote Link to comment Share on other sites More sharing options...
black sunshine Posted October 24, 2006 Report Share Posted October 24, 2006 I was wondering what or how to guage the compression difference from altitude to altitude. I was recently at Sand Mountain Nevada and i checked my compression up there and it was 145-150 lbs what should it be in Santa Rosa California which is probably close if not sea level. and what is safe to run my compression to with out blowing up the motor. i heard to run it between 175 and 200 lbs with race gas would be just fine any suggestions. I could be wrong but it shouldnt vary more than 15 psi. I think sea level is 14.7psi and the further you go up in the atmosphere the less it gets. I dont know the elevation of sand mountain but lets guess it is higher than Santa rosa, your readings there will be lower than your results in cali. Quote Link to comment Share on other sites More sharing options...
Animalman294 Posted October 24, 2006 Report Share Posted October 24, 2006 Here is a compression chart................. Approximate Cranking Compression These pressures are estimates based on fresh stock bore, piston, porting, and deck height. It is recommended to check your compression after installation. Sea Level 1000' 2000' 3000' 4000' 5000' 18cc 197 178 171 170 165 145 19cc 183 167 160 158 152 137 20cc 169 156 149 146 140 129 21cc 156 145 138 134 128 121 stock 130 125 118 112 106 100 Sand Mountain Nevada is at approximately 4000-4500' depending on where you are at. So on stock bike the difference is approximately 33 #'s and on a modified bike the difference is more drastic 42 #'s. But you need to check it at either end............... :beer: Quote Link to comment Share on other sites More sharing options...
Fastashell69 Posted October 24, 2006 Author Report Share Posted October 24, 2006 OK i went down and got a compression tester and my reading yesterday was 170 and at sand mountain it was 145. but maybe i didnt have the 14mm adapter on it so maybe it wasnt far enough down to get a right reading. And what benefit will i get by having more compression? Quote Link to comment Share on other sites More sharing options...
Animalman294 Posted October 26, 2006 Report Share Posted October 26, 2006 The higher the compression, the more pressure pushing down on the piston when it fires and gives you more power and torque. When you get up above say 155-160 you need to run race gas to keep the motor from detonating and getting to hot.............. :beer: Quote Link to comment Share on other sites More sharing options...
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