94 vmax 600 deluxe 5 mpg

bks81

bks81

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Joined
Jan 18, 2014
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Location
Rensselaer, IN
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(153.8) 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.
 

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.
 
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.
 
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.
 
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
 
yammy said:
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
Click to expand...

Oh yeah, I have already replaced the primary clutch with one out of a 96 vmax and it was rebuilt and in great shape.
 
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
 
Zack1978 said:
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
Click to expand...

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.
 
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?
 
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/snowmob...g a Sled/Jetting a sled and reading plugs.htm
 
Thank you Bornyamaha, the info there helps. I went ahead and finished going thru the carbs today, made sure they were good and clean, used air compressor to blow thru all passages. put it back together the witout any changes. The air screws were 1.25" out, I put them back in and set at 1 1/8 turns out, the only change. But I decided I better check the choke plungers to make sure they were set right. I tell you what, that is tough to do. I ended up turning the adjusstment in about 3/16" on each choke cable to be sure the plungers were all the way seated. I may have a little too much slack in the cables, but wanted to make sure the plungers were seated. But all said and done, it started fine, so I guess the choke is still working. took it out for a short drive, stopped and pulled plugs to inspect, and they were brownish colored. So then I went for a 4 mile drive at all throttle ranges. runs good at low speed and 3/4 and above range, but it just aint right at 3/8-5/8 throttle. It seems like it is almost missing instead of running smoothly. Would this be fixed by moving the needle ering?
Below is a pic of my plugs after the 4 mile ride.

Thanks for your help,
Brian
plug2.jpg
 
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theres the main problem I believe ,you say you have one size mains, bigger than stock.. well those sleds came from the factory fat, ( one size to big ) what I did and most everyone else did ,back in the day, was to drop one size from stock and lower the needles down one notch, in your case it would be two sizes on the mains . It made a world of difference in mpg. I went from 85 miles to the tank to 110 miles to the tank! just be sure you check your plugs and make sure they run cardboard brown, and you will be fine!
 
What was the temperature when you did the test ride? It may blubber in mid range in warm temps - from running rich. Try lowering the needles one notch or see what happens when it is colder. I agree with the above on the main jet - use the stock size.
Check your fuel mileage now, plungers may have been leaking. Five MPG is excessive and you are correct, the carb settings should not change it that much.
 
the temp was around 32 F ... From what I have learned about this sled/carbs, you can adjust the low range (idle to 1/4 throttle) via the pilot jet and air adjustment screw, the midrange (1/4 to 3/4 throttle) via the eclip on the needle, and the high range 3/4 to wot) via the main jet. So my problem is in the midrange, so will be adjusting the eclip on the needle. Will not worry about the main jet as I am not in that "range" very much as 3/4 throttle = 70+ mph ... I am normally 65 or under 90% of the time. And even if I were in high range alot, the 1 size bigger jet only equates to 4.87 ounces more per hour then the stock standard size main jet. Not enough to get me maybe .5 mpg better. Once I get the low range and midrange tuned in, I think I can get 8-10 mpg, which would be more normal and I would be happy with that. I will let you all know the outcome when I can get some miles on the sled. Thanks for alll your help.

Brian in IN
94 Vmax 600 Deluxe
 
Just an update. I moved the e-clip from the 3rd slot on the needles up to the 2nd from the top. It definitly made a difference in how it ran. And this weekend we were able to take the sleds out for a 18 mile ride out in the fields, me on the Vmax and the wife on the Cougar. I filled them both up before we started and reset the tripometers. Now remember that last year when I ran out of gas at 50 miles, the Cougar still had 1/2 a tank. So I got them back home and then filled them both up again to find out how much gas each one used. I was thrilled to find out the Vmax used 2 3/4 gals and the Cougar used 2 5/8 gallons. Now if you figure the mileage it comes to 6.73 mpg which aint great, but I'm assuming that riding in loose packed snow, and in drifts will yield worse mileage then on the groomed trails. But I'm thrilled that the Vmax used just a hair more fuel then the Cougar, so I think I'm on the right track. I have checked the plugs several times after short test runs and after this 18 mile ride, and have seen one plug being brown and the other being a Charcoal black. Would it be not unussual to have one carb run a little richer then the other? Would you suggest I leave it alone, or try moving the eclip on the richer carb to the top most slot. I would of course check the plugs many times to make sure its not too lean afterwards.
 
Are you still running with the jets one size over? If so you should drop it two sizes. Like priors said everyone myself included dropped the mains one down as they were jetted way to high.
 
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