Mm700 won’t idle

B

Bart Elder

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Joined
Jan 28, 2024
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12
Hi guys. I just bought a 2002 mountain max 700 141. All stock. 2600 miles. I’m in Denver Colorado. The machine came from steamboat and I presume it was jetted properly for that altitude, around 9000 feet. I rode the sled once, at around that same elevation. The sled starts easily with full choke when cold, then flip it to half choke to let it warm up. Even after warmed up, I flip the choke off and it dies. Then I flip the choke to half, get it up to 1/2 throttle and she goes. I flip the choke off as soon as she goes. I rode it for an hour like this and it seems jetted properly from about 1/3 throttle to wide open. Again, she won’t idle, but then I flip to half choke and she will . I turned up the idle screw in 1/4 turn increments and that worked for a few seconds, then she would die again unless I flipped to half choke. I turned the idle up one total turn , now I’ll back it out to where I found it. So I’m thinking she’s lean on pilot circuit. Before I pull the carb rack and clean pilot jets, then back fuel screws out 1/4 turn to give it more gas on idling, I figured I’d better ask the experts . Thanks for any help. By the way this sled is in very good condition so I hope I can get the carbs tune properly . Also, even when warm she needs half choke to start and then fires right up one pull.
 
Bart Elder said:
Hi guys. I just bought a 2002 mountain max 700 141. All stock. 2600 miles. I’m in Denver Colorado. The machine came from steamboat and I presume it was jetted properly for that altitude, around 9000 feet. I rode the sled once, at around that same elevation. The sled starts easily with full choke when cold, then flip it to half choke to let it warm up. Even after warmed up, I flip the choke off and it dies. Then I flip the choke to half, get it up to 1/2 throttle and she goes. I flip the choke off as soon as she goes. I rode it for an hour like this and it seems jetted properly from about 1/3 throttle to wide open. Again, she won’t idle, but then I flip to half choke and she will . I turned up the idle screw in 1/4 turn increments and that worked for a few seconds, then she would die again unless I flipped to half choke. I turned the idle up one total turn , now I’ll back it out to where I found it. So I’m thinking she’s lean on pilot circuit. Before I pull the carb rack and clean pilot jets, then back fuel screws out 1/4 turn to give it more gas on idling, I figured I’d better ask the experts . Thanks for any help. By the way this sled is in very good condition so I hope I can get the carbs tune properly . Also, even when warm she needs half choke to start and then fires right up one pull.
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Simple fix. Pilot jets are gummed up. Common issue if not cleaned every couple years. Will need to rejet carbs also for expected elevation of usage.
 
Davey jones said:
Simple fix. Pilot jets are gummed up. Common issue if not cleaned every couple years. Will need to rejet carbs also for expected elevation of usage.
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Thanks a ton. Gimme an inch I’ll take a mile: so you recommend my first trouble shooting steps be pull the carb rack, remove and clean the pilot jets then reinstall everything and test? Meaning , don’t mess with the fuel screws while I’m in there (which makes sense to not mess with them, just clean pilots and only make one change at a time?). Also, whatever I do I’ve got to pull the carb rack. Anytime tips for that? Thanks again
 
Bart Elder said:
Thanks a ton. Gimme an inch I’ll take a mile: so you recommend my first trouble shooting steps be pull the carb rack, remove and clean the pilot jets then reinstall everything and test? Meaning , don’t mess with the fuel screws while I’m in there (which makes sense to not mess with them, just clean pilots and only make one change at a time?). Also, whatever I do I’ve got to pull the carb rack. Anytime tips for that? Thanks again
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Well you need to clean main jets also and carb bowls etc. Pilot and main jets may just need to be replaced and idle air screw adjusted depending on what altitude prior owner set it at and altitude you will run at primarily. Did you get the owners manual? It will have baseline settings for various temps and altitude. Same variables can apply to clutch tuning.
 
Davey jones said:
Well you need to clean main jets also and carb bowls etc. Pilot and main jets may just need to be replaced and idle air screw adjusted depending on what altitude prior owner set it at and altitude you will run at primarily. Did you get the owners manual? It will have baseline settings for various temps and altitude. Same variables can apply to clutch tuning.
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Thanks again. I just wondered what the best way to pull the 3 carb rack is? Whether or not I should pull airbox, etc. first. Probably I should. That way I can pull the carbs back and out off the intake manifold boots. I’ll do as you say and clean pilot jets and main. I’ll see how many turns from fully seated in the idle air screws are so I know . I don’t have the manual but I can get some baseline settings . The machine lived at an altitude, 9000 feet, and was probably jetted properly at some point. I’ll be running it again at 9000 feet. So maybe it’s just clogged pilot jets. We’ll see. Thank you
 
Bart Elder said:
Thanks again. I just wondered what the best way to pull the 3 carb rack is? Whether or not I should pull airbox, etc. first. Probably I should. That way I can pull the carbs back and out off the intake manifold boots. I’ll do as you say and clean pilot jets and main. I’ll see how many turns from fully seated in the idle air screws are so I know . I don’t have the manual but I can get some baseline settings . The machine lived at an altitude, 9000 feet, and was probably jetted properly at some point. I’ll be running it again at 9000 feet. So maybe it’s just clogged pilot jets. We’ll see. Thank you
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Yes, do remove air box for sure.
 
Will do. Nice sunny day here in Denver 50s. Were you at? Im 53, moved to Colorado from Jackson, Michigan in 1992. First work on sleds in 1983. Piece of junk 73 motoski 295 and a 1974 snojet 440
 
Bart Elder said:
Will do. Nice sunny day here in Denver 50s. Were you at? Im 53, moved to Colorado from Jackson, Michigan in 1992. First work on sleds in 1983. Piece of junk 73 motoski 295 and a 1974 snojet 440
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Northern Indiana. Wife and I leave Wednesday for the month of February riding in Quebec. Have owned over 40 Yamahas since 70s.
 
Oh man. So cool. I mostly ride Yamaha . The best . I do have 4 Honda mini bikes for the wife and 10 and 7 year old boys. My current and last 4 dirtbikes have been Yamaha. Update : I just fired the sled to confirm issue is: she won’t idle without choke. Yes. Still the issue. And now I find all 3 idle air screws are FULLY SEATED IN. On this machine , you said it’s an air screw. So someone has turned them all the way in to try to fix the lean condition. Is that correct, on this machine you turn the idle air screws in for less air, and out for more? My confusion comes from some four stroke engines it’s a FUEL screw. And thus out would be more FUEL. Sorry to ramble: the question is: when I turn the air idle screws OUT, is this as doing more air or fuel ? Thanks again for the advice
 
Bart Elder said:
Oh man. So cool. I mostly ride Yamaha . The best . I do have 4 Honda mini bikes for the wife and 10 and 7 year old boys. My current and last 4 dirtbikes have been Yamaha. Update : I just fired the sled to confirm issue is: she won’t idle without choke. Yes. Still the issue. And now I find all 3 idle air screws are FULLY SEATED IN. On this machine , you said it’s an air screw. So someone has turned them all the way in to try to fix the lean condition. Is that correct, on this machine you turn the idle air screws in for less air, and out for more? My confusion comes from some four stroke engines it’s a FUEL screw. And thus out would be more FUEL. Sorry to ramble: the question is: when I turn the air idle screws OUT, is this as doing more air or fuel ? Thanks again for the advice
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Might I contact you directly? I wonder where I can find pilot and main jetting recommendations, and general air/ screw starting point like 1 and 1/2 turns out . Thanks again . I’m new to this forum . Not sure is it’s ok to share my number 303.527.1531 or if email address but here it is . Thanks again
 
Bart Elder said:
Might I contact you directly? I wonder where I can find pilot and main jetting recommendations, and general air/ screw starting point like 1 and 1/2 turns out . Thanks again . I’m new to this forum . Not sure is it’s ok to share my number 303.527.1531 or if email address but here it is . Thanks again
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Sorry. I’m getting dumber by the day. I wasn’t on the air idle screws but the bowl drains. I’ll pull the carbs like I should have done in the first place
 
Bart Elder said:
Oh man. So cool. I mostly ride Yamaha . The best . I do have 4 Honda mini bikes for the wife and 10 and 7 year old boys. My current and last 4 dirtbikes have been Yamaha. Update : I just fired the sled to confirm issue is: she won’t idle without choke. Yes. Still the issue. And now I find all 3 idle air screws are FULLY SEATED IN. On this machine , you said it’s an air screw. So someone has turned them all the way in to try to fix the lean condition. Is that correct, on this machine you turn the idle air screws in for less air, and out for more? My confusion comes from some four stroke engines it’s a FUEL screw. And thus out would be more FUEL. Sorry to ramble: the question is: when I turn the air idle screws OUT, is this as doing more air or fuel ? Thanks again for the advice
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All the way in is Wrong. Out is more fuel flow at idle. Could be your issue? 1.5 turns out is a good start point
 
Sure enough 3 blocked pilot jets. All clean now. I’ll put it back together and hopefully she’ll idle now. Idle air screws were at 2 and 1/4 out. Thanks again
 
Bart Elder said:
Sure enough 3 blocked pilot jets. All clean now. I’ll put it back together and hopefully she’ll idle now. Idle air screws were at 2 and 1/4 out. Thanks again
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Thanks again. I put it all back together today snd she seemed to start and idle fine now that the pilot jets are clean. I cleaned with a single wire brush bristle, then soaked in pine sol, then rinsed, then wd 40, carb cleaner , then a bit of grease on the threads one float bowl gaskets before reassembly
 
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