1994 VMAX 600 awful MPG's and oil consumption - jetting and clutch

Z

Zack1978

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Dec 12, 2005
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Hi everyone,
Many of you responded to my other thread related originally my 1994 VMAX 600 running poorly, that evolved into a poor MGP thread. I figured it would be useful in the future in terms of searching to make a dedicated VMAX 600 MPG thread.
The general consensus is that the clutch might be an issue, or the carburetors. I have no objection to spending a bit of money to attempt to rectify the poor gas mileage, I just need some specific advice on what to purchase. I leave the sled in a snowmobile storage facility about 4 hours from my home, so I have no direct access to it. I will be mailing any parts that I order to the mechanic at the storage facility for him to install. He is not a VMAX 600 expert, but he is a good sled mechanic in general.
The basic info that I have is that the compression numbers are : Port : 135, Starboard :140. What do you think of the compression numbers? Currently the sled is achieving about 5-6 MPG. The carbs were cleaned recently. I also replaced the belt at the onset of my ride recently, with a new OEM Yamaha belt. With the new belt on, I did notice some squealing when the sled was at idle. Is that normal with a new belt? Is the noise indicative of an issue?

Some of the suggestions to solve the poor gas mileage were:

1. Stuck/broken choke cable - I ordered a new aftermarket cable, it will be installed soon. If the snow holds out I can see if that does the trick.

2. Wrong jetting - I am almost 100% confident that the sled is jetted as it was when it left the factory in 1994. So what jet(s) should I go with? Here is the link to the jetting chart: http://www.zenitram-inc.com/Manuals/VmaxJet94.jpg it looks like the MJ # 156.3 is the OEM jet setting. What should I jet it at and still be safe? 153.8? In order to change the jetting, all I need is two new main jets?

3. Here is the text of another VMAX MPG thread, does the needle jet response seem plausible? "There is a known issue with the carbs. When the fuel econmy goes down the toilet you should change the needle jets. Over time the inside diameter increases and allows more part throttle fuel through. Changing the needle clip position is not going to help much. Just go through the carbs and replace the needle jets with the same # as before just new ones. A Yamaha Dealer mentioned this to me last weekend. I was getting less than 5 MPG but then again my bowl drain needle came out on the Mag side carb." In the picture of the carb here (http://www.ronniesmailorder.com/fiche_section_detail.asp?section=3898766&category=Snowmobiles&make=Yamaha&year=1994&fveh=176153), what number is the needle jet? 4? Do I need two?

4. Clutch Issues. The sled has about 1,900 miles on it, but I have read that the 1994 clutches were a weak spot of the sled. Is there a 100% direct replacement clutch that will be an upgrade over the OEM clutch? If so, what clutch should I buy? The clutch could also be causing some drag on the engine. I would rather not have a clutch issue deep in the woods, so now seems like the time to upgrade it.

Oil consumption

No ideas at all on how to cure this issue.


Thank you everyone!

Zack
 
I don't think the twins are great on gas anyway but it should be better than 5-6mpg. I have not really drove mine a lot since I bought my srx but I am going to guess somewhere around 10 mpg is what I am getting in it now. It has 80 miles since a fill up and has 2-3 gallons left in the tank. I am not familiar with the clutches on the 94. I have read a lot of people switch it over to the 95-96 style. Clutches can have a big impact on fuel consumption. I have also read the twins are hard on clutch bushings. My clutch was wore out to the point I thought I blew the motor on my 96. Worked great when I got it at 2300 miles then about 30 miles later wouldn't work right at all. If you are going through more fuel it will use more oil too. The oil is mixed in the fuel pump. Hope this helps
 
I really doubt you need new needles, what you most def. need is smaller main jets , one size smaller would help out immensely, and lower your needles one full notch! You do that and rebuild your clutch,..(.roller bushings are the main culprit) put new slides on the secondary and you wont believe the difference your gas and oil consumption will be! also...when was the last time that skid was rebuilt...idlers and bushings and things like that can bind up a suspension pretty good and cause excessive load on that motor...time to do some simple maintenance work ,is probably all it needs!
 
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Those sleds are pigs, every one ive ever rode with got PP consumption. As mentioned the "newer" clutch upgrade might help a bit, but I think its the nature of those slugs.... All you can do is make sure everythings working how it should. Can you easily spin the track by hand?
 
153.8s will be fine. R & R the seat too. 25+ year old seats tend to contribute to the p!ss poor MPGs your getting. Remove skid and eliminate drag by replacing all bearings w/ at least abec 3 grade bearings.

The generic number for each skid bearing is incorporated into the yamaha part #.
https://partstream.arinet.com/Mobil...oGso9lgJRul3j3AO52eIesS1ERXEyAmiR54zGe01.html
Look at the bearing part # and you'll see a 6004 in it. That's the generic # for that bearing.
http://pages.ebay.com/link/?nav=item.view&alt=web&id=251488445399
 
I think everyone has good answers here, As far as the clutches go, the primarys seem to be some of the most durable in the industry at least at that time. I have seen some yami sleds with 9,000+ miles before the clutches were touched. That definitely cant be said for a Comet. The 94 secondarys are another story though. They work great when they are fresh but tend to lose proper shift rather quickly after a rebuild.
 
im surprised about the bad mpg's. i had a 94 that use to average around 12. your vmax sounds like my ex-exciter. bad mpg's will lead to a divorce, at least for me it did. the bright side its always fun finding a newer model
 
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