Broken W-Arms 03/04 - explanation

[LazyBastard]

Ever notice that its the big sleds that break W-arms and not the little ones like 600's? With the high rate of damaged W-arms on the RX1, I have seen a number of people hypothesize that its the additional weight of the sled that causes the W-arms to break... that it is somehow related to the suspension being bottomed out harshly on account of the extra weight.

This is not the case.

Fact is that its actually the POWER of the engine that causes the W-arms to break. Specifically, the amount of forward pressure along the rails that has to be transferred into the W-arm.

In the image attached, you can see two possibilities for W-arm breakage. In the lower image, you can see that the force against the W-arm would cause it to break from the TOP. This is not consistent with what really happens. The W-arm cracks from the BOTTOM.

In the UPPER image, you can see that the force A against the W-arm is countered by force B applied by the LIMITER strap, causing a split to form from the BOTTOM of the W-arm.

On top of this, a characteristic behaviour of a broken W-arm is excessive track ratcheting. Note that if the crack had formed at the TOP of the W-arm, then applying force would cause the crack to tighten up and no excessive ratcheting would be experienced. Being that the crack forms at the BOTTOM, applying force C will cause the W-arm to bend in a manner which will result in the track LOOSENING. Also note that NO MATTER HOW MUCH you tighten the track, it will still ratchet, and in fact, the more you tighten the track, the more the W-arm bends and the more likely it is to COMPLETELY break off.


SOLUTION: to prevent the W-arm from breaking:
Solution #1: Reinforce the BOTTOM of the W-arm at the point where the limiter strap comes over.
Solution #2: Relocate the strap to the more traditional placement - from the main crossover bar to a bracket affixed between the rails forward of the current placement. This will prevent force B from being applied at all and direct all force straight ALONG the W-arm.
Solution #3: Reduce the angle that the W-arm makes with the rails. This can be accomplished by making a custom W-arm that is LONGER than the current one, and tightening the limter straps further. This will REDUCE, but not eliminate force B. This solution will also require similar extensions to the lower control rods and rear arm, and will require a longer track.

 

[snowsweat]

That is an excellent analysis of the problem. I believe you are mostly right but that the truth is actually a combination of two things. It seems that sleds with poorly set up suspensions are especially prone to broken W arms. Many people reduce the front spring pressure in an effort to keep inside ski lift down or make the steering more positive. When the front arm bottoms out, the rubber bumber is supposed to contact both the rails and the cross shaft directly above it. In some sleds, this bumber is missing or the cross shaft is not there (Venture's and Warriors). This leads to excessive localized loads near the bumber.
When you add this to what you have described, combined with the heavier weight (more bottoming) and higher speeds (more bottoming), the arm gets worked both ways and tends to fatique.
(An improperly set up control rod will also spell doom for these arms.)

 

[LazyBastard]

Some sleds don't have the bottom stops at all for either top or bottom... they bottom on the shock. Thats fine. Cranking in the straps won't cause any stress on the arm, it'll be distributed straight onto the shaft or shock when it hits bottom. Letting the straps OUT makes it REALLY bad. Also, setting the control rods for too much transfer creates additional load against the W arm that they would otherwise take. Any damage caused by bottoming out would show at the TOP, and I have yet to hear of a W-arm showing ANY sign of stress at the top.

 

[BETHEVIPER]

the reason the w arm breaks on the bottom is the upper shaft hits it from above, bending it between the w arm mount at the rail and the end of the warm at the tunnel. this added with the stress from the straps snapping tight in the middle pulling down on the warm at this point every time the suspenion is unloaded adds up. another cause is that the factory bushings in the front shock are loose from the day they are new and get worse from there. this casues the arm to bottom befor the shock rubber bottoms, this causes the suspension to travel alittle too far past bottoming. putting more stress on the middle of the arm against the center shaft instead of against the shock mounts and the tunnel.
another cause of this is the lower shock mount starting to turn on the older model (pre 00)skids. when this turns it can even make the shock dig into the track and or break off causing much damage.

the cure is to install bearings into the front shock. this will cure the sloppy bushing problem. it will in theory make the front shock work better as it doesnt have to take up the slack of the bushing before reacting to the movement in or out.
make sure the bumpers are installed and that the lower arm mount is not shifted or bowed in any way. if yours is damaged at all install a newer version, they are stiffer and slotted to help from twisting under.

just my observations from years of seeing people needlessly ruin their sleds.

 

[nhrxrider]

I'm attaching a pic of my broken W arm. You can see in the top left corner of the pic that there is rust around the break point...that point was the first crack, which is why it rusted over time because I never noticed it was broke. Because of that break, the arm flexed, and continued to break across the arm at the weakest points. Notice the right side of the arm is still held together. Basically it broke at the top first, then continued to work across the arm. Luckily I found the damage during a greasing session before the last part of the arm broke.

Jim

 

[LazyBastard]

Wow. Thats definitely not the same phenomenon as most W-arm breaks... I would *guess* that you probably hit something hard on ONE SIDE, maybe you had a ton of ICE jammed into the right side, allowing the left side to continue compressing on a nasty.

 

[nhrxrider]

It might have weakened on the same ride when I broke the relay rods. (another pic attached). I had to SLOWLY ride out about 20-30 miles with NO rear suspension (completely bottomed) inching along. Because of the day, time of day, and location, there were few other riders...in fact, I didn't see a single sled on my way out...so I couldn't have left the sled and caught a ride out. I was forced to ride it. That was around 1000 miles before the W arm broke.

Basically, in my opinion, the '03 and '04 skids were junk. In a matter of 4,000 miles or so, all bushings were worn out, both relay rods broke, the W arm broke, one shock was bent (and ready to break), and from day 1 of ownership there was no compromise to get a decent ride...either set it up so it won't bottom on hard bumps and big trail dips, but live with a very harsh ride over little bumps; or soften it up for the small stuff and deal with the spine breaking bottoming when a big bump would sneak up on me. The Cat suspension cost me half of what a replacement W arm would have, and fixed everything I ever complained about with the stock suspension.

Jim

 

[snowsweat]

At the shop where I worked, we've seen a couple of broken control rods but no broken pull rods. That part was defective. However, it is possible to set up the springs so poorly (extremely soft rear spring, tight front) so that the pull rods operate in compression on occasion, which obviously bends them.

 

[4Fighter]

Thanks for pointing this out. It just looks like another Yamaha design flaw. IMO: aside from the power-plant, the sled is a joke. I've never in all my years of snowmobiling have had a new sled that needed new or "stronger W-arms, or having to weld braces and brackets here-or-there, shock adjusters that freeze-up, or a $350.00 shock upgrade that still has to be revalved, or a $1500 aftermarket suspension (with exception to my 92 Jag 440). My '95 XLT rode better. However, in all fairness, I've never had a 4-stroke snowmobile either. M10's are great if you've got an older sled, but why should they be needed on a '04? To fix an OEM screw-up perhaps?

I may have jumped the gun a little early by giving the sled any pre-mature praise, at least while riding it on a smooth trail, or lake. I'm definitely NOT satisfied with my purchase, and I WILL let Yamaha know about it. Now that you've pointed out that stress from the engine may attribute to the W-ARM failure :shock: , what the is that? Ironically, I received a "last chance for Y.E.S." notice in the mail yesterday. The last time I was at the dealer (for a cracked W-ARM and jammed locking collar - center shock), Yamaha told them NOT to replace any more shocks on my sled. It didn't matter that both mechanics showed me how to make adjustments previously, and how tight to tighten the locking collars either.

The components on this sled are junk, and you can guess where I'm telling them to put that $1500.00 fee for an extended warranty? I just don't have the resources to buy more parts for this sled. I used to spend money on unnecessary hop-op parts, now it's just to get the damn thing back on the trail, and my wife is getting very upset. [If momma aint happy, nobody's happy] There's two RX1's for sale in the local paper, mine would make it 3, if that says anything at all about the '03 - '04's

 

[nhrxrider]

Thats about how I feel. I think I can name a bit more about the sled that I loke, and I have to say that Yamaha built a hell of a sled which just had typical first-year flaws (funny they carried over to the second year though), but what upset me is that they won't stand behind what goes wrong. When I bought the sled, my 2-stroke friends were a bit envious, and curious about how it would do. When they saw the power, they were impressed. Then when the track fell apart, and even before that it had no traction, they began to shy away from the RX. After a few hundred miles, when it started using oil, the 2-stroke guys kind of laughed that I had to add oil just like them (one of my strong arguments for a 4-stroke...just top off the gas and ride, no oil...now I put in a quart every other tank of fuel). Anyone who tried the sled complained about the suspension and handling (until I put in the Cat skid). Which brings me to another point I have to agree with...why is it that its an UPGRADE to put in a 7 year old suspension design in a 2 year old sled??? I have a '98 Cat skid, and it worked miracles. Funny.

Jim

 

[4Fighter]

Jim,

If you agree with me then, write a letter to Yamaha. I am. There's so many things that I want to tell them, I can't keep it under 3 pages long. I just get more upset and throw more words on the paper. -see?

There's simply no excuse, other than poor engineering and design strategy, that I can think of why we ('03-'04 owners) got burned on this. As much as Yamaha is taking a chance on dropping 2-strokes, you'd think they would want all the positive publicity they could get. I could eventually see past the oil issue, but getting beat to a pulp everytime the trail gets a little bumpy is something I'm not willing to tolerate. Escecially when the alternative is to use a 7 year-old suspension on a 2 year old sled.

 

[BOUNTYHUNTER]

Nicely done LB as it seems very logical and I liked your drawing showing possible solutions to this problem.

The rest of you make great points as well, seems some of you might not be as impressed with your sled as I am with mine. But in all fairness I bleed Yamaha blue and red.

But here is my problem I have with this overall "W-Arm" thing, Im just not seeing any. There's no doubt in my mind that some of you guys are or have experienced problems with the "W-Arms". But out of the 30 RX 1's that left here in 03 none ever had a failure, the same for the 04's. Every single sled that has come back for any general work, was inspected and the "W-Arm" was checked just because of what was being said here on TY. I spoke to a buddy of mine who works at another Yamaha dealership and out of the 60 RX 1's they sold in 03, one failure due to hitting a log under some fresh snow. No one here in Manitoba is seeing that, and our Yamaha rep confirmed that as well this spring durring our spring 05 showing.

At the present time I'm waiting for Matt from the Speed Shop to send me a set of quick adjusting nuts for my 04 Warrior. I have the skid out so I though I would also put new Red sliders and matching Red wheels into the skid seeing how it was out. Then after reading this post I decided to completly rip the skid down to the bare bones and do a real test on this baby. I cleaned the skid then brush blasted the "W-Arms" now that I had a truly clean surface I "Die Pened" the "W-Arms". Then with a lighted 10x magnifying glass I inspected every inch of that skid, and nothing came up to raise an eyebrow.

I ride double on my Warrior more often than I do by myself, and I punish my sled some day's. By launching it across driveways while ditch banging it, Blair Morgan would be proud of the air time I get. On the rivers, creeks and trails we always have the ski's up and pound her through the rough stuff. You would think if those things were going to break they should have already or show signs of fatigue, cracks or something. There is only 2,000 miles on my sled, but lots of other sleds we have looked at had anywhere's from 3,000 to 6,000 miles on them.

LB any thought's on this as to why?

How many of you guys out there have had no problems with your "W-Arms"?

Cubby old buddy; you seem to always have your skid out, anything with yours?

 

[LazyBastard]

I was pretty skeptical about the whole idea too, until I realized that mine was broken. It just broke at the end of last season (finished the season and had to rip it apart), ~5k miles.

 

[BOUNTYHUNTER]

I forgot to mention how I have the skid set up

Rear control rod nuts are all the way up to the start of saftey thread

FRA is set at hard

Rear shock clicker is set at one turn from max, and the shock adjusting nut is set one notch up from stock

W-Arm strap nuts are two turns more from stock [3/8 of an inch through the nut]

Front shock adjusting nut is one full turn down from stock

Front end is 1 1/4 turns down from no load

LB keeping in mind I ride double, with the new Simmons Ski's I have coming they will eliminate any darting or wandering and should be even more aggressive. Will the front end need to be lighten up with those ski's?

What's your thought's?

If your thinking I have the skid set up pretty stiff, your right but have never bottom it out yet at that set up nor any "W-Arm" problems.

 

[LazyBastard]

You shouldn't need to adjust the front end for the skis.