The Skinny on Darting…

 

 

 

 

 

 

OK, here's the scoop on Yamaha's darting problem, and I'm finding this to be true with other brands as well. This is true for sleds new and old, regardless of ski type or material.

In February 2000, my wife and I bought our first new sleds. Two identical Yamaha Vmax 500's, sleepy silver. We were told at the time, that they were 'state of the art' snowmobiles, and I wondered about those steel skis...

We were soon made aware of a serious darting problem with both of these sleds. I knew it wasn't in set up, assembly, or any of the excuses we got at the dealer. It was happening equally in both sleds.

I began a search for a cure, and quickly found no help. I talked to about 50 people from all over the industry, and no one provided useful information on the subject. I was soon looking at trading in for another brand!

I bought two pairs of C&A Pro skis, as I was told these would cure the problem. Well, they didn't! But they sure carved better! And steered lighter too. I was happy with the skis themselves, but I knew I had to dig deeper into my sled to find an answer.

It came while talking to Scott Bergstrom, who mentioned an old school fix of placing shims behind the ski spindle. He explained that the shim forces the rear of the ski down, and usually fixed the problem. I happened to go to Hacker's Yamaha the next week, and spoke with Rick. He concurred that a shim would do the trick. I was renewed with my mission!

The factories design sleds with many necessary factors, most we never know about, if we did, we'd be engineers working for them. One of the built in parameters on Yamaha's in particular (that baffles people to no end) is what we'll call, 'ski runner pressure'. SRP for short.

 

SRP is not what you think! It's not how many pounds are on each ski.  That would be the combined weight of sled and rider, plus additional gear, divided by a bunch of algebraic equations that would make me puke. SRP, for our purposes, is the balance from front to rear.

 

             Specifically, the nature of how the weight is distributed through the wear bar, keel, and the rest of the ski.

On most Yamaha models, we find a darting problem, and no adjustments can fix it. I have two '00 Vmax 500's, keep in mind that all sleds from '97 and up which came with steel skis are the same in this respect. The exception, usually, seems to be the SRX. I find that only a few of these sleds have darting problems.

With regards to sleds with factory steel skis, the problem lies, 95% of the time, in the SRP. After talking with a Yamaha engineer, I knew I was on to something! He claimed that before '97, Yamaha made the SRP so it was rear biased. They got complaints about this, and switched to a front bias. I thought to myself, how about a middle ground???? Duh!

So with the help of a couple of people in the industry, Scott Bergstrom and Mr. Hacker, I set out with a plan. With an old drive belt in one hand, and a hack saw in the other, I made my first set of shims.

Shims? Yes, shims. Super easy to make, and all you have to do is dig that belt you threw away out of the garbage can.

Cut the shim to fit tightly inside the ski spindle. You can measure it, or hold the belt up and mark it with a pencil. Either way, you need the shim to fit snugly under the spindle.

The next step is to place it on top of the rubber bumper. Each brand has a different shape and size spindle and bumper, so be prepared to test and see what results are best for your sled.

I recommend putting the shim on top of the ski bumper, and gluing or screwing them in. Your choice. They will fall out the next time you cross a road or jump through the air, which was what happened in my case. When the pressure that holds it in is gone, like when the ski tip is pushed upward, the little shim will be history. I used RTV with good results.

When putting them in, tilt the sled onto one side, and have a buddy push the ski tip upward until you make sufficient room for the shim. They should fit snug! Glue or screw from here.

Now, I know I'll be asked questions about specific models, so I'll try to answer them right now.

Steel ski sleds, came with a plain ski bumper. Use the full height belt shim. Your darting will be all but gone.

Plastic ski sleds came with an 'S' code bumper, which is taller in the rear than the plain unit. With these, I found the full height shim to be a little too much. It's your option to whack off the 'lugs' on the inside of the belt, but in doing so, you should be just right.

The factory Yamaha plastic skis have a mounting block under the spindle, so the shim may need to be tweaked a bit for sleds so equipped. Here's what you're looking for in all cases, any brand or model:

With fresh wear bars, the front carbide pad (or 2" front of center) should be 1/8"-3/16" off the ground, with the rear touching. Do this with a flat surface, of course!

This goes for any brand of sled, any brand of ski, wear bar, or what ever. What you'll have, is a ski/wear bar that slices into ruts, and carves their own grove.

Spend the time doing this mod, if it doesn't work, you've got something seriously wrong!

 

Here's how my story goes. I bought $600 worth of skis and wear bars, only to realize that it wasn't the skis. I did gain performance with the C&A Pro's, and highly recommend them. I wore out the Bottom Line carbides in short order, and talked to Scott Bergstrom. He made bars for my application, and parted with some wisdom I'm grateful for. Another product of his I highly recommend with any ski, is his 'Ski Savers'. They help 'hide' the bar from ruts, and help cut down on darting somewhat. They add two additional 90* edges to help any ski carve like your uncle on Thanksgiving. They also protect the ski very well.

Now, you're asking yourself if you should believe this. Is this right for me? Is this my problem? Go out to your sled right now, and look at the wear patterns of your wear bars. If you see a tapering toward the front, thinner in front than rear, then you stand to cure your darting by this method. If not, set up your sleds front end, something is wrong. If so, do the mod, and thank me later.

I get emails from guys who's wife's sled darts all over, or the ass end swings all over the trail. Wives complain more than guys! It's also why the live longer, when something is wrong, they go to the doc and fix it! Guys are supposed to be tough, so if your sled darts, and you think its manly to take up two lanes of the trail, think again.

 

Here's the set up I wound up with:

C&A skis

Plain ski bumpers

Full height shims

Bergstrom Ski Savers, any length will help

4" Bergstrom Skegs carbide wear bars

 

Let me say that I do not run studs in either sled. If the ass of your sleds wags like a dog at any time, you're darting! Studs don't help darting! Fix the SRP, and you'll cure your problems.

Both of my sleds now carve very hard, in all conditions. Powder snow is the one exception, but the C&A's dig in very well there too. There are times on trails where I have to slow myself down in corners. It surprises me how fast I can take a hairpin, and if I let my mind wonder, I'll keep pushing it until I scare myself.

Good luck with your set up, remember to play with your suspension set up, make it right for your weight and riding style, you'll be much happier with your sled.

 

 

John Guest