700 SX Problems

Y

YamahaArctic

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Feb 10, 2004
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Here's the story. I got a 1997 700 SX with 4000 miles on it. It has Carbon Tech low tension reeds, bender triple pipes(with clutch kit), reed spacers, and recently just added tempa flow. I live at about 1300 feet, so I use Benders suggested jets for the carbs(150 mains, 55 pilots, 1.5 out on airscrews, needles in position 3). About two weeks ago we went for a ride at night(temp was -10F), so I figured I would be just about right since bender's setup is a little rich, well anyway I kept fouling plugs. Fouling plugs made me think it was rich, but anyways I cleaned all the plugs and finished the ride with no further problems. The following weekend on the river(temp was 5F) the motor seemed to run great until about 85mph then it would lose rpm and feel like it was running out of fuel or lean. At this point I couldn't figured out why one night it was fouling plugs then the next it felt like it was lean, especially since the temp change wasn't that much. So I went out and bought a tempa flow to hopefully solve this problem, I installed jets for -20F according to tempaflow's instructions( 152.5 mains). Went out to ride on the same spot on the river(temp 15F) did the same thing, but now the plugs were black, not wet, but like carbon black. So last night I put 150 mains back in tried it out in a field, ran the sled wide open for about 20 seconds, then hit the kill switch, the plugs looked lean again!! Top speed has fallen to about 95mph on the speedo, it feels really strong in the low and mid range, but the top end feels wierd. Reeds look great, cleaned and cleaned the carbs. I just don't get it!! I was wondering if it could be and ignition problem(had my stator replaced last year)?
 
check this

If you get your vent lines full of fuel the tempa flow will act up. Maxdlx
 
No, I haven't check the compression yet, but it seems wierd it would start doing this all of a sudden based on low compression, plus all three plugs look the same. I have thought about the vent lines, and will address tonight, then try it out, thanks.
 
set up

My first suggestion would be to give each change a hundred miles to really zoom in on. Keep in mind new plugs do NOT coat up for about 20 or so miles, and will look very lean if you install and run down a field and back.

I am at the same elevation and run 150's / 52.5 pilots -this is the bender revised set up by the way / 1.75 turns out, and needles 3-4-3.

I have run to 34 below with no problems, and checked plugs at 25f after wot shut down, and just a touch dark.

I would clean carbs out, check floats, and reinstall making sure your airbox boots are sealed nicely around carbs. Be sure your airbox is clear and that your reds look good as long as the carbs are off.

If that doesnt doi it (it should) you probably have the mystery stator on your hands. (I doubt it, but they will act odd)

Oh - be sure you havent worn a hole in the pipes where they overlap either.

Good Luck!
 
While you are doing all the above make sur you check all your motor mounts. My SX was falling on its face at 85 and all it was was a loose motor mount. I found it after messing with everything else.


Tod
 
You say the sled falls off on the top end and you have the Carbon Tech low tension reeds. Could that be your problem? I would think the mid tension reeds would be a better solution for you. Carbon Techs web site used to say something like the following:
low tension - low to mid range performance weaker top end
mid tension - strong mid range thru top
hi tension - weak low end strong top end performance
This won't address your jetting issues, but might explain why it falls off so much on the top.
 
reeds

put the stockers back in. i have a set if you need them. I run the carbon tech mids and they are great
 
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