Question about breaking W arms

H

Hebi

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May 16, 2004
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Edgerton, WI
Ive heard a lot about people breaking the W arms on their sleds.
Im a little bit concerned about this and Id like to know why it happens and how it happens.
It seems that it is most common on '03 and '04 RX-1s. The explanation that I found over on rx1.info was that the engine has so much torque that when the when you accelerate that it essentially tries to bend the w arms.
Is this because when you accelerate it essentailly "unloads" the front part of the rear suspension which causes the front W arm to sort of "lock" which puts stress on it?
Ive also heard of this happening on SX Vipers. Ive heard people claim that if you set the control rods so that it has a lot of weight transfer that it will increase the likelyhood of breaking W arms. Is this as big of a problem on the Vipers as it is on the RXs?
If I come upon a sweet deal on an SX Viper should I pass on it because of this problem or is it something that can be avoided?
Hebi
 
it is not a hard problem to fix if it does break. It breaks as a result of the front arm bottoming out, usually caused by very hard hits in the front of the skid, too much weight transfer (the decreased coupling allows the front arm to work independently of the rear shock, so when it hits a bump it bottoms much more easily) I have never heard anything about too much torque causing it to break, sounds like a load of crap. Good thing is that if it cracks, or even if it hasn't yet, you can easily strengthen it up with some gussets welded into the corners, then it wont break. Definately never stopped me from riding and beating on my yammy's.
 
hehehe- NONONO - It doesnt break due to the uncontrolable 4 stroke power -

The w arms have been breaking since 1997 when the suspension was intoduced (or should I say 1996) Originally the center shock was also the stop. When the shock hit bottom it would mushroom the cap on the shock. All the gas was lost and eventually the shock would actually come apart an possibly go into the track (they all have issues) Then Y added a rubber stop that fit in the w arm and would make contact with the slide rail (rather than the shock bottoming) The w arms were/are made of very light steel and actually crack/break at welds. This was caused by riding in moguls hard and steel flex. Preload to the center shock or valving did help but eventually they break. To my surprise yamaha never made a real heavy duty arm to his day (max performance does) In addition the lower bracket (bracket #4) often had bolts come out and the ears would break off over time. (this isthe bracket that the limiter straps wrap around) The entire center shock zone has been a weak link in the pro action since day one. (really all sleds take the most abuse here when ridinghard in the moguls)
 
Suspension should always bottom eventually, but yes if you valve/spring properly you will minimize it crashing out. Not to say the stress/flex over time wont take its toll.
 
correct, if you run the center preload tigher, or get the center shock revalved, and let out the limiters further, and decrease the weight transfer (increase the coupling), this will all help the W-arm to not break. Its when you set it up for a lot of transfer and then go pounding moguls that they usually break. if it does break, one good fix and its fine for good.
 
You can set the suspension up to almost eliminate the possibility of breaking the W arms, but if you ride it hard through the bumps you still run the risk of breaking them.
Essentially, its not a deal-breaker in terms of if you would or would not buy a Viper...
Thanks,
Hebi
 
brother broke the w-arm on his srx,and we beefed it up with gussets.. it broke just below the center of the w, where the bar is for the limiter straps,the bump stops on the early models are shot after a few rides, between ice build up and taking a beating they will fall out.y came out with larger ones that stay in the w-arm better. we yanked the skid and welded it up.pretty whimpy metal the stock w-arm is made out of.
 
when I did my track swap I sandblasted my W-arm and after 2500mile of hard riding it was just fine, I did weld in a few small gussets and painted it up and re-installed it. I know of 2 Yamaha's around here that busted there W-arm, BOTH were running quick adjusts and liked to "wheelie" the sled (I never saw the fun of lifting the skis 6 inches off the ground, makes it hard to turn while on the throttl)
 
I broke several w arms and 2 of them were with stock transfer and coupling settings.
The xtc's were really bad because they used a spring from a bic pen. (and the twin 600's had bad pistons)
Again, if you change valving and spring rate you can minimize damage, but if it gets rough - you hammer down and that shock starts to fade - ck you rw arm, but not until you get home...
 
i had one hit that was SO hard this winter that it broke my motor mount from the impact, and it hit directly on the front arm of the rear suspension. It was a pretty darn high jump and i landed right on top of a mogul, and it kicked back so bad, and broke the pto side rear motor mount (the cheap aluminum one), and i checked over the suspension for a good 15 mins, and i could not BELIEVE that the w-arm didn't break. I got lucky on that one for sure.
 
holic - the vipers were known for breaking that motor mount - very common. You probably took most of the blow on the front. The w arms in my experience break after long term abuse. Did you check bracket # 4
 
Bracket 4 is the bar that attaches inside of both slide rails. It has "ears" that bolt to slide rails, and often times these ears will break, and especially if you loose one of the bolts in the ear allowing this entire bar/bracket to try and rotate. This is the bar/bracket that your limiter straps are connected to oppostite the W arm. You sometimes really have to look to see if it is broken, because only one side at a time breaks. Usually at the weld point of the round bar and the ear. Be sure to zoom in.
 
yea i had my whole suspension out and looked everything over, and its all good, i was really surprised. As for the motor mount, i actually have an SXR, not a viper. The yamaha dealer told me the vipers have that problem, but said he has never seen anyone break one on an SX. He's like, are you sure you didnt bend your frame with a landing that hard? lol. Still drives straight and there is no noticeable damage or fatigue.
 
I bent a drive shaft once from some hard landing- You almost cant tell, but you get a mild vibration at speed. i never broke a sx mount either, but I did have to align my clutches at leat once per season. (It was simply out of spec)
 
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