Compression Ratio

[AVBANSHEE03]

Can some one help me out here? I need some one to break down the compression ratio's for me. 4 example (6.5:1) Im arguing w/ my friend about the shees stock compression. Ive had 2 shees and both of them have had between 120- 125 no less. He says stock comp. is 95. and how does elevation affect comp. Im at mia,fl. if it matters. thanx

[Lepew]

I don't know how elevation will effect comp. But I know at sea level a stock banshee should have @ 125 lbs. of compression new. I have info that a stock banshee has a 7.6-1 compression ratio but I don't know how that was figured on a two stroke. Good liuck on the argueing, just remember your friends

[sredish]

Can some one help me out here? I need some one to break down the compression ratio's for me. 4 example (6.5:1) Im arguing w/ my friend about the shees stock compression. Ive had 2 shees and both of them have had between 120- 125 no less. He says stock comp. is 95. and how does elevation affect comp. Im at mia,fl. if it matters. thanx

Yamaha wants the stock compression to be between 125 and 130 at sea level. If you have a bike at sea level and it has 130 lbs. and then you take it to 5,000', the compression will drop to, say, 105 lbs. because the air is less dense. It's very important to factor in the elevation when looking at compression numbers. That's why if you take a carburated motor from sea level to say the Rocky Mountains, it runs like shit because it needs to be tuned for the higher elevation and less air.

 

I'm at 600' and my banshee stock was at 127 lbs. If it said 95lbs., I'd be getting a new top end in that bitch, especially if I was in Miami at sea level.

 

One thing I don't know, is how to figure actual ratios, like 10:1, or 7:1. I don't know that. I just know what I said above. I hope that helps.

[AVBANSHEE03]

Thanks alot, I learned something new today. I know that factory specs say comp ratio is 6.5:1 but im just going to keep going by pounds and not complicate my self. Thanx again for that info on elevation and air I didnt think it was that important.