ASK THE MXPERTS: ARE YAMAHA YZ450F FRAMES BREAKING?

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Dear MXA,
I have heard reports of Yamaha YZ450F frames breaking. Are they true? Where do they break? Is there a way to fix them? Sorry for the questions, but I own a 2016 YZ450F and want to know.

This was the crack that happened on some 2007 Yamaha aluminum frames.

MXA has seen a current Yamaha YZ450F frame with cracked welds at the head tube area. This is not a new problem, but the reoccurence of a previous frame breakage issue that MXA first reported on back in 2007. The problem went away with the next version of the Yamaha aluminum frame, but seems to have resurfaced on the latest 2014-2016 editions.

In our opinion, this is cold-weld issue at the factory level. We don’t consider it common, but MXA has personally seen a cracked frame (and sent the photo below to Yamaha for their perusal). These photos should be enough to convince you to look closely at your frame at regular intervals—like before every race.

This is the crack on a 2015 Yamaha aluminum frame.

If your frame shows signs of cracking, the protocol is to talk to your friendly local dealer first. He should act as an ombudsman between you and Yamaha. It should be possible to resolve the issue at the dealer level. However, if that fails don’t give up. The next step is to contact Yamaha’s customer service representative directly. Yamaha has been known to give new frames to customers with cracked frames. It depends on age, condition and usage.

If you fail to find satisfaction at Yamaha, you can fix the problem yourself, but it requires skilled help. Since the cracks are a weld problem and not an issue with the aluminum tubing or the frame itself, you could have the crack rewelded (by an experienced welder in your area). Listen to your welder about the feasibility of fixing the crack by rewelding it. Luckily, the aluminum in the head tube area is fairly thick and consists of forgings. Here is how to go about it.

(1) Drill small pilot holes at each end of the crack and use a grinder to chamfer the drilled holes. This will stop the crack from spreading underneath your new weld.

(2) Next, take a grinder and grind the cracked weld down. You want to make about a quarter inch V-shaped groove in the existing weld. The aluminum in his section is 8mm thick, so some caution is required. You don’t have to neatly remove the old weld, just get down to the base metal.

(3) Finally, take the time to preheat the frame over a fairly large area. You should be able to heliarc the crack with little or no trouble. This should only be attempted by a certified welder and with the correct rod. In other words, we don’t recommend that you do it without professional advice.