fuel screw adjustment on 700 mtn max

scrud · Dec 18, 2009

I'm new to the mtn max and was wondering if it's possible to adjust the fuel screws with the carbs on the machine--it's a 2002 mtn max 700.

The manual I have says to adjust the idle to 1,500 rpms and then adjust each carb with the fuel screw until the motor reaches the highest rpms and then readjust the main idle screw again.

I just can't figure out how I'm going to adjust the fuel screws with the carbs attached

. Any suggestions?

Thanks

Mountain Boy · Dec 18, 2009

The screws you are looking for are underneath the carbs. PITA. There are several aftermarket companies that build adjusters that you can adjust the screws with out taken the carbs off. (Bender, Northern Lites, MTN Performance all have designs that work.) with that said I have set mine and never have fiddled with them. I have Air Knobs by Northern Lites and they would be handy if they (carbs) fell out of tune, It has been set , forget it for me. My .02

snowdad4 · Dec 18, 2009

not sure what book your reading that gives you that misinformation, all the yamaha manuals give you a specific number of turns out for a given altitude and temp. i have that info if you need it. like mentioned in the above post, its a set and forget, as per specs.

SRXSRULE · Dec 19, 2009

Man the things I forget about untill someone makes a post like this bringing it up.

Adjusting the fuel screws is most noticable right when you get into the throttle. I had remote adjusters on all my 2-strokes and adjusted them often when temp changes. This was manily when I was drag racing ice/snow/grass.

Unless you have remote adjusters you have to remove the carbs to adjust them, then put everything back together and test drive it, then re-adjust. good times. Eric

scrud · Dec 19, 2009

snowdad4 said:
not sure what book your reading that gives you that misinformation, all the yamaha manuals give you a specific number of turns out for a given altitude and temp. i have that info if you need it. like mentioned in the above post, its a set and forget, as per specs.

The manual I bought is the Clymer Manual. It was my understanding the purpose of adjusting all three fuel screws when the motor was running was to get them all in sync as close as possible? Anyway, doesn't look like that's going to happen unless I buy some aftermarket stuff.

Is it going to be tuned close enough if I just set them all the same turns out?

I'm always messing with the air screw on my dirbikes every time I ride in a different elevation. I'm assuming the fuel screw has the same effect and didn't want to have to remove the carbs every time, take a guess at the adjustment, and then hope it was right after installing.

Thanks for the info.

SRXSRULE · Dec 19, 2009

Most of the time you do have all 3 adjusted the same amount. The fuel screw works together with the pilot jet. If you have the correct pilot and main jet in for temp and elv your fuel screws will be about 1.5-1.75 turns out. Eric

SD Coyote · Dec 20, 2009

snowdad4 said:
not sure what book your reading that gives you that misinformation, all the yamaha manuals give you a specific number of turns out for a given altitude and temp. i have that info if you need it. like mentioned in the above post, its a set and forget, as per specs.

x2 You just need to set for alt. and temp that you are riding. An easy way to get them right is to turn them in until lightly seated. Now put a mark with felt marker at each end of the screw slot. Now back out 11/2 or 13/4 or 2, whatever is needed. As you go higher & warmer you set the mains and needles leaner. This causes a too lean condition in the low end. That is why richer pilots and turning out fuel screws is required. Just set fuel screws exactly the same. Snodad will give you the specs, if you don't have them.

scrud · Dec 20, 2009

snowdad4 said:
not sure what book your reading that gives you that misinformation, all the yamaha manuals give you a specific number of turns out for a given altitude and temp. i have that info if you need it. like mentioned in the above post, its a set and forget, as per specs.

Snodad, could you send me the specs, please.

thanks.

snowdad4 · Dec 20, 2009

i need your normal or target altitude, and current carb info, ie., pilots, mains, amd needle setting.

scrud · Dec 21, 2009

snowdad4 said:
i need your normal or target altitude, and current carb info, ie., pilots, mains, amd needle setting.

Mostly I ride anywhere from 6-10,000 ft. The jetting when I bought the sled was this:

Pilot--62.5
Main--130
needle setting--1st position
Fuel screw 2.5 turns out.

I thought this was too lean--although I never rode it with these settings.

I changed it to this:

Pilot--62.5
Main--132.5
Needle setting--2nd position washer above and below clip
Fuel screw 2.25 turns out.

I rode it around the yard a couple of days ago with the new settings. It's been warm for this time of year--upper 30's. I noticed when I gave it full throttle it went pretty good, but after a short full throttle followed by a quick release, while the RPM's were coming back down if I pressed the throttle again, it would really bog until the motor came back down for a few seconds. I'm thinking it has to do with fuel screw setting, but not sure.

Thanks for all the help.

snowdad4 · Dec 21, 2009

your really close right now for conservative jetting. i dont know where you were test riding at, but could be a lean bog due to considerably lower elevation? if your cruising the yard at 3000', and your set up for 8-10000, you should have a bog. i would leave it where its at until you get up high. turning the screws in makes it leaner on the pilot circuit, turning out make it richer. what altutude was the test run?

mysledblows · Dec 22, 2009

I rode it around the yard a couple of days ago with the new settings. It's been warm for this time of year--upper 30's. I noticed when I gave it full throttle it went pretty good, but after a short full throttle followed by a quick release, while the RPM's were coming back down if I pressed the throttle again, it would really bog until the motor came back down for a few seconds. I'm thinking it has to do with fuel screw setting, but not sure.

Might want to check the throttle cable tension. It sounds like you might be kicking in the TORS system and when you let it "come back down for a few seconds" it resets itself.

scrud · Dec 22, 2009

snodad: The elevation I did the test ride is about 4,600 ft. So maybe it is just a little on the lean side. I'll try at a higher elevation and see how it runs.

mysledblows: Do you think the throttle tension is too tight or too loose to activate the TORS? I need to check the freeplay to see where that's at.

snowdad4 · Dec 22, 2009

scrud said:
snodad: The elevation I did the test ride is about 4,600 ft. So maybe it is just a little on the lean side. I'll try at a higher elevation and see how it runs.

mysledblows: Do you think the throttle tension is too tight or too loose to activate the TORS? I need to check the freeplay to see where that's at.

too tight will activate tors. you want 2-3mm(almost 1/8") freeplay on the throttle lever before it pulls the carb rack. make sure your idle is set at 15-1600rpm first. also, 2 1/8 turns is what i was showing for your fuel screw, but i wouldnt adjust it if your sure your at 2 1/4. that will make you a tad leaner. wish i lived at 4600'.

scrud · Dec 23, 2009

snowdad4 said:
too tight will activate tors. you want 2-3mm(almost 1/8") freeplay on the throttle lever before it pulls the carb rack. make sure your idle is set at 15-1600rpm first. also, 2 1/8 turns is what i was showing for your fuel screw, but i wouldnt adjust it if your sure your at 2 1/4. that will make you a tad leaner. wish i lived at 4600'.

There's plenty of room here, so come on over. I'll check the freeplay in the throttle hopefully today sometime(I don't know if I left any). Is it possible I could have the choke set too tight also? I think I set that with no freeplay.

Thinking back on it, I don't believe it bogged before I changed to richer jetting. I never rode it, just started it a few times to load it on the trailer to transport and then a few times in the garage. I'm hoping it's just something with the cables when I reinstalled.

snowdad4 · Dec 23, 2009

choke cable freeplay, as per yamaha specs, .5-1.5mm, before the bracket on the carb rack starts to move. trailer is loaded, sleds are fueled, adding some ski guides to the sleddeck ramp, where am i going?

scrud · Dec 24, 2009

snowdad4 said:
choke cable freeplay, as per yamaha specs, .5-1.5mm, before the bracket on the carb rack starts to move. trailer is loaded, sleds are fueled, adding some ski guides to the sleddeck ramp, where am i going?

Southeastern Idaho! Although we only have about a 1/2" of snow on the ground right now. I hear the higher elevations to the north have quite a bit.

I am such an idiot. I went over all the throttle freeplay and choke free play. Both were too tight, so I adjusted them. Still bogged. Got checking all the wires to make sure I had everything hooked up right and discovered I hadn't hooked up the TORS wires the right way. When I put it back together, I only remembered two wires. Well, I plugged both wires coming from the carbs together instead of plugging them into the two wires coming from the throttle. Plugged it together the right way and lo and behold, no bog

. Now I just have a hanging idle

. I think I either have a leak in the air boot or too lean on the fuel screw. I'll have to mess with that over the weekend.

Thanks again for all the help.

Powderat · Jan 2, 2010

Hanging Idle....

Just thought I might throw in my 2 cents, If your carbs are clean and your TORS is adjusted right and operating correctly. Try lowering your throttle down 2 or 3 hundred rpms and see if it drops for you. If not, try 2 3/4 turns on pilot screws. You might have to go to the next larger pilot jet. Lets see if snowdad4 and the rest agree with me. These are just problems I have messed with before as have alot of other MM owners. Go to http://www.totallyamaha.net/forums/ This site is the ONLY site for Yamahas. Best group of guys on the web.

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fuel screw adjustment on 700 mtn max

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