Mountain Max 700 Triple BOGGING wont go over 6500 RPM

A

a.beam.reach

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Jan 1, 2021
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Location
Bend, Oregon
We just picked up some used sleds. . . we are new to the sport but we are hooked.

The 1997 Yamaha Mountain Max 700 Triple ran poorly so l pulled the carb and cleaned it. Oddly, because the rest of the machine is filthy, the carbs actually looked pretty good. The 700 really didn't do any better. Pulled the carbs to see if I missed something. Seemed to run better but couldn't thoroughly test until I got it to the mountain. At the mountain. . . seems to run up to about 6500 rpm okay but won't go past 6500. . . then just bogs down. Spitting tons of oil / gas sludge out of the pipes. See pictures: IMG_3091.jpgIMG_3090.jpg I read this great tutorial on how to clean the carbs: https://totallyamaha.com/snowmobiles/aaTECH/carbs/cleaning_carbs.htm and noted that I neglected to pull the fuel mixture screws and clean. I cleaned them (like the rest of the carb really wasn't dirty) and also made minor adjustments to the floats per this tutorial: https://totallyamaha.com/snowmobiles/aaTECH/floats_adjust/Carb_Float Adjustment.htm I ran the motor (lifted the back and ran it up . .. not at the mountain) and still runs like crap. Here is a link to a video:
HELP. . . what am I missing? What should I check out next?
 
a.beam.reach said:
We just picked up some used sleds. . . we are new to the sport but we are hooked.

The 1997 Yamaha Mountain Max 700 Triple ran poorly so l pulled the carb and cleaned it. Oddly, because the rest of the machine is filthy, the carbs actually looked pretty good. The 700 really didn't do any better. Pulled the carbs to see if I missed something. Seemed to run better but couldn't thoroughly test until I got it to the mountain. At the mountain. . . seems to run up to about 6500 rpm okay but won't go past 6500. . . then just bogs down. Spitting tons of oil / gas sludge out of the pipes. See pictures: View attachment 66054View attachment 66053 I read this great tutorial on how to clean the carbs: https://totallyamaha.com/snowmobiles/aaTECH/carbs/cleaning_carbs.htm and noted that I neglected to pull the fuel mixture screws and clean. I cleaned them (like the rest of the carb really wasn't dirty) and also made minor adjustments to the floats per this tutorial: https://totallyamaha.com/snowmobiles/aaTECH/floats_adjust/Carb_Float Adjustment.htm I ran the motor (lifted the back and ran it up . .. not at the mountain) and still runs like crap. Here is a link to a video:
HELP. . . what am I missing? What should I check out next?
Click to expand...

I can see the main nozzle is lifting up on its own as you rev it up, which means that either the main jet isn't screwed into the bottom of it, or the piece in between the main jet and nozzle is missing.
 
Also, the 97's were known for leaking at that joint, so they used a different type of fitting there in 98. However, there is a piston-ring type gasket there, so make sure it is in there and/or not broken or wore out.
 
Yep, never seen anything like that before, those brass parts moving shouldn’t be moving, lol.
 
Thank you . . .. I put it back together the way it came apart BUT the main washer (pictured below) was installed the wrong direction! Wish I would have caught this earlier. Thankfully, I didn't reinstall the air box this time so it will be a quick job. Hoping to post a success story tomorrow. Thanks guys!

carbimg13.jpg
 
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