Sx 700 mid range burble

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03machstock

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Feb 8, 2022
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Hi guys, I picked up a 99 sx 700 this year that had been sitting for about 10 years. I cleaned the carbs and replaced all the jets and float needles/seats and had her out for the first time. It ran excellent when idling/all the way up to wot, and throttle response was so crisp. The only issues seem to be that at constant midrange throttle it seems to have a slight stumble/rough running/ burble to it. I’m not sure if it’s just jetted a little fat, or if that’s just the way these things run. If you give it gas the raspy/ slight breakup/ burble instantly goes away into good smooth power. The sled also seemed to drink a ton of fuel on the 30 mile trail loop I was on. I didn’t keep track because I didn’t start with a full tank, but I think I used over half a tank. Should I lean the needle jets out? I was going to clean the carbs again and put them in my new ultrasonic cleaner for good measure. Sled is bone stock except for reed cage mod, and it’s in near mint condition with 1200 miles. It was very well taken care of. Any ideas?
 
Needle jets shouldn't be worn with that many miles, but given it's hard on fuel and is rich in the midrange, that's what I'd look at first.
 
reed cage mod? then it has reed spacers? reed spacers do take away alot of that so called burble you mentioned.if the clutching is right and the drive train free then you should get 10- 12 miles a gallon! what are you reving to?
 
yammy said:
reed cage mod? then it has reed spacers? reed spacers do take away alot of that so called burble you mentioned.if the clutching is right and the drive train free then you should get 10- 12 miles a gallon! what are you reving to?
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Yea, the mod where you grind away an area of the top cage, it does the same thing as reed spacers. I found it on this forum. Clutching is stock, it’s over reving a little bit, and I’m going to clutch it next season, just wanted her to run smooth first. Clutches are currently clean as a whistle.
 
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I just completely disassembled the carbs as much as I could with leaving them on the rack. I’m going to put them in the ultrasonic cleaner up to about an inch below where the throttle shaft is. I found the needles with the clip in the center (3rd slot). With both plastic washers under the clip. Would moving both plastic washers above the clip be too drastic of a change?
 
good range for a tripple yamaha is around the 120 mile mark.

check that the clutches move freely without the springs and all the rollers move. i would then check all the bearings in the suspension if you haven't and repack them all including the jack shaft bearing and the speedo/drive axle bearing. i would throw a new primary clutch spring in it while i was in there ($15.00 canadian) as the one in there was under load in the clutch for 23 years if it is oe and i know from experiance that they get weak over time and cause issues.
 
03machstock said:
I just completely disassembled the carbs as much as I could with leaving them on the rack. I’m going to put them in the ultrasonic cleaner up to about an inch below where the throttle shaft is. I found the needles with the clip in the center (3rd slot). With both plastic washers under the clip. Would moving both plastic washers above the clip be too drastic of a change?
Click to expand...
Run one plastic washer on top one on bottom will clean up the burble especially in the 20 to 30 degree weather just be careful not to run wide open in 0 degree weather because it does lean it out a little more
 
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