Compression range on 650?

I'm going to look at another cycle tomorrow. This one's an '82 650 Maxim. Can someone tell me what the compression range is for these bikes?

Thanks.

 

compression ratio X atmospheric pressure + atmospheric pressure = compression pressure.

9.2 X 12.7 + 12.7 = 133
that's at 4000 altitude. at sea level. it would be 147. sea level atmospheric pressure is 14.7. you lose .5 for every 1000 feet above sea level.

here's what the manual says though. at sea level

Standard 156
Minimum 128
Maximum 171

Maximum Difference between cylinders 14

 

128 psi min to 171 psi max-- max 14 psi between cylinders.

 

Looks like about the same as a 750, then. Thanks, guys!

 

My 650 pushed 149-153 across the board, cold, when I looked at it.

 

Thanks, Fitz.

 

Why thank Fitz? Much as I like the guy, he never answered your question.

 

Ohfercryinoutloud. I didn't need to. His question was already answered by snowwy66, I was simply contributing my own real-world experience in purchasing a used 650 (13K for reference, Bay, and a serious POS but it blew great numbers and it's ALL there.)

MY thanks go out to snowwy for directly answering his question; I can't fault the guy for not having a manual until he buys the bike to go with it.

I was away from my books at the time, or I might have beat him to it.

 

For what it's worth, I thanked Fitz at that point because his reply came after I had I expressed my thanks to you and snowwy who had responded earlier. Your mother and I love all you kids the same!

Also, I did end up buying the bike even though it turned out to be a 1980. I'll post details later and maybe a pic or two.

 

So, at sea level, that works out to ~150psi. Where does the 171 come from? Atomized fuel in the mix? Momentum of air 'stuffing' the cylinder? Just curious...

 

The book.

 

Well, ask a silly question...

 

Ideal gas laws, the compressed gas is hotter, exerts more pressure, and there is a "limit" to compressibility, on a sliding scale.

 

if the motor is running perfect. compression will always be higher then the math dictactes. i've yet to see a perfect engine come out as low as the math.

my suzi has 160 pounds. but the math calls for 140. my yamaha wasn't up to par as for what the book says. it only had 140. still higher then the math though at 133.

air expands with heat. and combustion. they teach you that in school. and is also taught in pilot school but as a different method.

in pilot school it is taught that air expands in the summer. making it thinner. a single engine cessna can fly higher altitude in the winter when the air is thicker then it can in the summer when air is thinner. 12,000 feet is the limit in summer where as 14000 feet would be the limit in the winter. (((IF I REMEMBER RIGHT))).

 

Bandits at 6 O'clock, snowwy, watch those high comp' readings, it can mean a carbon build up............

 

carbon buildup comes from leaded gas. which no longer exists.

my comp readings are in line with what the manual says.

 

Carbon can build up from sources other than leaded gas; blow-by or small amounts of oil from a marginal valve stem seal or just overly-rich running can all cause carbon to build up.

 

Rat-tat-tat-tat...
Take that you foul deposits...