Cause of cracked W arm?

norwegian

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Joined
Nov 5, 2004
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2,903
Age
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norway
Hi, all of you with cracked W arms. Have you checked your center shock? I had a blown center shock and it caused the front arm to bottom at every bump. Do people still break the w arms even with a good center shock?
 

Its a poor design and needs reinforcement welded in. I also remove the rail stops and that will help some.. the shock bottoms out before it hits the rails anyway so with the correct spring set up and valving you dont need the stops. In the original form it hits the rail stops first then it trys to bend the arm over the stops... stops are actually to close to the pivot point. This is my 2 cents.
 
there are a few things going on. the design was to bottom the shock and arm at the same time. When everything is new, this happens. as the bushings age, almost imediately, it makes the shock bottom out way after the arm bottoms and bends around the bumpers. This also happens when the shock rubber gets smashed out of the shock. Also, the shock preload is held against the limiter straps bending the arm the other way when not compressed. This combined with a thin arm material, and many, many undercut welds at this flexing point causes the problems.

best case fix,
bearings or tight bushings in shocks
tightened bushings in w arm, add grease fittings to lower mount
keep bumpers in w arm to take load off shock bumper
reweld cracks and slide a solid piece up through the inside of the W arm tube and spotweld a couple times on each end.
It will last for ever.
 
and all this time I thought it was bumps that caused this . . . LOL

If I was smart I would have welded reinforcement gussets before they broke, but I always waited until after they were broken to weld them up. Got another one this year to do.
 
After three or four weld jobs on my 97 I finally ordered a new one from Yamaha. Took to weeks to get it and was an updated version. My other option was to build a new one out of some 4130 tubing.

Considering the pounding the suspension takes it's amazing it holds up for a day.
 


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