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Thread: 94 vmax 600 deluxe 5 mpg

  1. #1
    Junior Member Mini bks81's Avatar
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    Default 94 vmax 600 deluxe 5 mpg

    I found out last year that I am only getting 51 miles to a tank of gas (appr. 10 gals) on the trails in MI and am guessing the carbs need to be adjusted properly. I bought the sled used 2-3 years ago and dont know if the previous owner re-jetted the carbs or not. My daughter was on a 98 Arctic Cat Panther 550 Dlx LC following behind me. And when I ran out of gas, the Panther still had a hair under a half a tank. Both were filled up at the same time and both went the same miles. I can smell that the Yamaha exhaust is richer then the Panthers.
    So I finally tore into the carbs today. According to the manual, I am supposed to have a main jet size of 156.3. and instead I have main jet size 157.5, which is 1 size bigger. and the jet needle clip is in position 3, which is where it should be. Surely just 1 size bigger jet wont cause me to get 5 mpg will it? I checked the air adjustment screws and they are 1.25 turns out and the pilot jet is a 52.5. WOuld you reccommend me to put a 1 size smaller jet(153. in to increase my mpg, or just the reccommended size(156.3), or stay with what I have? or maybe just move the eclip on the needle jet? Oh and I snowmobile between 600 - 2000ft.
    I just got done replacing all the steering sissor bushings, collars, and nylon washers, and smeared them all down with grease inside and out before assembling to prolong life. And I installed new plastic skis also. The rear skid and gear case was gone over last year to make sure all is well there. Greased all the bogie wheel bearings, replaced if needed. jack shaft bearings and track drive bearings greased or replaced. I have done it all to make sure the sled doesnt break down on me any time soon. new track last year also.
    The sled has 4xxx miles on it, engine runs great besides running rich. I only put a couple hundred miles a year on it each year, seeing how Indiana doesnt keep snow on the ground much anymore.
    So all thats needed now is to increase my fuel mileage and its ready to go to WI next month.

  2. #2
    Junior Member Mini bks81's Avatar
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    ok, after some research I found out that the 157.5 jet will use 1.2 cc more fuel per minute at wot then the 156.3 jet. times this by say 60 minutes (I only got 50 miles per tank, average 50 mph = 60 mitues) 1.2 cc x 60 = 72 cc x 2 carbs = 144 cc ... this equals 4.87 ounces ..... not much ... so I think I will not worry about the jet size. But theres got to be another reason for the high fuel use then, maybe plugged passages in the carb? Where should I look? I would guess it would be a passage that carries air instead of fuel.

  3. #3
    VIP Member Mini
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    Not sure of the difference between the 94 vmax d and the 95 vmax sx twin but I have a 95 twin sx and 98 sx twin and they are the worst snowmobiles ever owned on fuel and oil. I carry extra oil with me just in case, for what it's worth.

  4. #4
    Senior Member Improved gbic1's Avatar
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    I guess I dont have an answer for you but my old 95 Vmax 600 ran great and would go 80 miles a tank. I bought it used and it had New carbs from previous owner. Never looked at jet size. That was the main reason I went to a 700 triple. It will do 100 miles a tank or more. I ride in the Northwoods of Wisconsin.
    1998 Vmax SX 700 Red Triple Ohlins RX1 skid shocks extended travel. Electric start and reverse 2013 20 2010 miles 760 2009 585 miles
    1998 Deluxe 700 Black electric start and reverse. 3 inch rise custom seat 2.5 PowerMadd risers

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    VIP Member yammy's Avatar
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    your problem is probably in the clutching , those primary's were bad bad bad , rollers were always goin out slide bushings were junk and the spiders were terrible... find a bettr primary to put on and youll be a lot better on fuel, or at least rebuid that one

  6. #6
    Junior Member Mini bks81's Avatar
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    Quote Originally Posted by yammy View Post
    your problem is probably in the clutching , those primary's were bad bad bad , rollers were always goin out slide bushings were junk and the spiders were terrible... find a bettr primary to put on and youll be a lot better on fuel, or at least rebuid that one
    Oh yeah, I have already replaced the primary clutch with one out of a 96 vmax and it was rebuilt and in great shape.

  7. #7


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    These VMAX MPG threads are starting to make me nervous about the new to me 1994 VMAX 600DX that I have. Any ideas what specific tips I should give the shop with respect to carb jetting and such to avoid 5 MPG?

    I know that the PO ran out of gas on the VMAX last year.


    Zack

  8. #8
    Junior Member Mini bks81's Avatar
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    Quote Originally Posted by Zack1978 View Post
    These VMAX MPG threads are starting to make me nervous about the new to me 1994 VMAX 600DX that I have. Any ideas what specific tips I should give the shop with respect to carb jetting and such to avoid 5 MPG?

    I know that the PO ran out of gas on the VMAX last year.


    Zack
    Zack, its not so much that anything needs to be changed. Its more so that everything needs to be in good condition. So if your shop just goes over the sled to make sure everything is in good order, the carbs are clean, and the 1 thing that they should pull off and check over really well is the primary clutch. Also make sure ski's are in good shape along with steering dont have play in it. My 94 vmax has 4xxx miles on it and probally hasnt had much maintanance done until I bought it 3 years ago.

  9. #9
    Junior Member Mini bks81's Avatar
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    OK, something I am wondering ... seeing how I have one size bigger main jets, can I move the eclip on the needle to setting 2? what exactly does the position of the eclip change or determine? Also, I am starting to figure out that the only way to determine if the carbs are set right is to look at the spark plugs. After I make changes of any sort, how soon do I check the plugs? 5 mins, 10 mins, 30 mins??? I have burnt holes in pistons on previous sleds and dont want to do it to any more. how will I tell between carbs set right and carbs set a little lean?

  10. #10
    Senior Member Stock
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    Please do some reading in the tech section. Check the link below. They are much better than me. On a side note yes the twin Vmaxes have always gotten terrible mpg but 5 is excessive. We have gotten as bad as 6 mpg on our "98" 500 but average is more like 8. There are several people on here the say they regularly get 10-12 but I have never been able to get near that with any consistency. Clutching and jetting are the first place to start. There are many other things to look at. Track rolling resistant, gearing, compression ...

    http://www.totallyamaha.com/snowmobi...ng%20plugs.htm

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