Opinion 97 sx 142.5 main jets?

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nytrodave

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I have 142.5 mains in my 97 700sx on all 3 cylinders. Altitude is 300-2500 feet, temps from 35F to -20F sled is stock. How confident should I be that these jets are not too lean??
 
Assuming the sled is stock and not modified, for temps above 0F at your elevation, your not really pushing it but as the temps drop you may lean out a little. If you typically ride at 10F and below, you should look into 145 mains. If you stay with the 142.5's, richen it up a little by going to 2 turns or more out on the fuel screw.
 
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I run 142.5 on my 99 600sx (760 BB) with no problems. I have ridden -0 degrees F. I dont lake race in those colder temps, but that jetting seems to do me justice so far. I would think that it would be fairly conservative for you, but use your own judgement, this is just my experience with my machine. Always best to start off conservative and work your way from there. I am also as 900-1000' elevation.
 
Dmace said:
Assuming the sled is stock and not modified, for temps above 0F at your elevation, your not really pushing it but as the temps drop you may lean out a little. If you typically ride at 10F and below, you should look into 145 mains. If you stay with the 142.5's, richen it up a little by going to 2 turns or more out on the fuel screw.
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You do relize the chart listed is for a 600 and the OP has a 700??? 142.5 are a slight lean for my taste especially with using poor fuel, ethanol. We run 143.5 in two and three with 145 in number one. At least in our 700's. Al
 
cajones2 said:
I run 142.5 on my 99 600sx (760 BB) with no problems. I have ridden -0 degrees F. I dont lake race in those colder temps, but that jetting seems to do me justice so far. I would think that it would be fairly conservative for you, but use your own judgement, this is just my experience with my machine.
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Your sled is a 600 and his is a 700, different jetting. Unless by "760 BB" you mean 760cc's...
alswagg said:
You do relize the chart listed is for a 600 and the OP has a 700???
Click to expand...
Apparently you don't realize the second chart on the bottom of the page is for 698cc engines... :rolleyes:
 
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I would say you'll be fine. Just no long pulls when it's real cold out. It should be crisp in warmer weather. I ran 145s with pipes at 1700' for over 5 years with no issues. wash and color was always good when spot checked! I would have your needles in stock position aswell if your sled is totally stock. I wouldn't worry about a can if you have one on.
 
I ride in -20F or colder at least once or twice a year. Before I put pipes on my 98 700sx I ran 142.5s across all three and even lowered the needles a .5 clip. I rode that way for 2 years without a problem. There are plenty who say not do it. But when it's that cold out I didn't do any lake racing either.

P.S. Quite a few will tell you that Yamaha's stock jetting errors a bit on the fat side. They do that for added protection.
 
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X2^^^on the fatness. Every motor will be a slight bit different. Just check your wash and plug color.
If you are worried, put 145 across the board and ride it for 1000's of trouble free miles. Unless you are a born racer, You won't feel the difference.
 
sleddineinar -> Same here...for about 7 years now. That is with stock pipe and muffer.

Dmace said:
Your sled is a 600 and his is a 700, different jetting. Unless by "760 BB" you mean 760cc's...

Apparently you don't realize the second chart on the bottom of the page is for 698cc engines... :rolleyes:
Click to expand...

My sled has been converted from a 600 stocker to 760 bore. So it is very close to the same displacement displacement. I apologize if I did not make that very clear. And again, start fat and work backwards from there until you are comfortable. As just mentioned, every sled is different due to manufacturing tolerences, start with 145 mains and work backwards while watching your plugs and piston wash. If you have an EGT guage, that can serve as a good feedback mechanism as well but at the end of the day, you need to watch your plugs and wash. Merry Christmas!
 
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