Need Help on 97 Yamaha MM 600 Jetting

[mccbrothers]

Wondering if anyone remembers what jetting works well on the 97 Mountain Max 600 twin with the smart carbs. Ride from 3000 ft. to 7500 ft. Starts running horrible at around 5000 ft. I pulled the carbs and first dropped down to a 155 main from a 160 then the pilot from a 55 to a 52.5, went up and it ran a little better but still wanted to fall on its face after 1/8 throttle, if I feathered the throttle I could get it going wide open and it ran decent on the top end, so I thought mid range and I removed the needles during the week and the clip was in the middle position one teflon washer on top of clip and one under so I left the clip in middle position and just took the teflon washer out from under and put it on top. This last weekend back up and around 5000 cutting out popping and falling on its face, don't think it is the tor switch cause it runs great at my shop 1000 ft. plugs look great also, could it be the smart carb, or do I just need to jet it down a whole bunch more, wish someone has a good running one and know s the main and pilot and needle position for a start, please help.

 

[mccbrothers]

SOmebody has to have a mm 600 for there wife

Common I know not everyone on here has brand new Yamys, I am so sick of hearing my brothers wife *****hh at me because her sled runs bad when she gets to the hills, would love some advice from some real yamaha mechanics, I know somebody on here had to have a Mountain Max 600 at one time or still do and know what a good starting spot is for jetting with the smart carbs?

 

[mysledblows]

Sorry mine had dumb carbs so I can't tell you what worked for me. They were pretty easy to jet though. 137.5 mains, needles at the top with one over and one under, 50 or 55 pilots. Don't remember for sure. This was at 9000'

 

[culvert]

You should be good with the 155MJ. I know I had the smart carbs and went to 150MJ and melted a piston. Went back to 155 and ran great from 2500' up to 8000'

 

[snowdad4]

have you adjusted the air/fuel screws to 2 turns out? this may help.

 

[mccbrothers]

You guys rock, Thanks

Giving me some good feedback, thank you very much, I will let you know after Sunday what changes I have done, and what it ran like, just put a 141 under it and drilled the suspension back 2in, the mtn performance template I had hanging on the shop wall from when I helped my buddy with his 700MM last year, seams to get good traction now just need to get the carbs working right, Thanks again for the feedback!!!

 

[mccbrothers]

Needle Position?

You should be good with the 155MJ. I know I had the smart carbs and went to 150MJ and melted a piston. Went back to 155 and ran great from 2500' up to 8000'

Did you have the needle in the top position like the other guy above had mentioned?