Inherent Yamaha problem

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10/7/2020 6:57 AM

Recently I had a freak mechanical problem which caused a large accident and numerous injuries. Just before a jump a rock caught the chain block at the rear sprocket and ripped it off at the welds on swingarm (showed no prior marks of stress) . As it wrapped up around the back wheel I went straight over the handlebars. Now that this has happened it seems like a very bad design compared to other brands I’ve ridden e.g KTM. I feel now that I have lost trust in the otherwise great bike that the yz450f is Photo
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10/7/2020 7:01 AM

Seen it happen on every brand. Oem and aftermarket.
Not common but it happens. Had one guy on a 18 ktm450 get a rock stuck and do the same thing also his350 got a rock stuck in his linkage and stopped his suspension. These are anomalies not in the norm.

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10/7/2020 7:07 AM
Edited Date/Time: 10/7/2020 7:08 AM

yzf162 wrote:

Seen it happen on every brand. Oem and aftermarket.
Not common but it happens. Had one guy on a 18 ktm450 get a rock stuck and ...more

I understand that anomalous mechanicals do occur however the bracket on a ktm is integrated into the swingarm when it is being cast; not welded. I’m not sure if other brands share the same design but the weld in my opinion creates a point of weakness that could be avoided.

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10/7/2020 7:08 AM

Sumbitch

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Alright Lunger, Let's Do It

10/7/2020 7:09 AM

If you don't like the idea of running an alloy chainguide go to a plastic option like the TM Designworks or Polisport etc. A lot more flexible. Or a carbon one which would just break with that sort of impact. Either way, a freak accident and certainly not common.

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November 13th, Forever in our memories !!

10/7/2020 7:09 AM

https://m.vitalmx.com/forums/Moto-Related,20/Japanese-manufacturers-can-we-have-an-honest-conversation-about-your-chain-guide-mounting-please,1372101

I’ve gone on a tirade about this before, the way the Japanese companies mount their chain guides is absolutely pathetic and embarrassing. It’s not a freak accident when those things pop off, it happens way more than people think and when it does the results can be ugly since it has a tendency to bring your back wheel to a sudden stop. The fact that they’re still just bird shit welding these things on (and missing with the automated welder half the time) is mind blowing to me.

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10/7/2020 7:10 AM

Happened on my ktm 450 as well. Just like yzf162 mentioned. This just happens.

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10/7/2020 7:19 AM

JM485 wrote:

...more

I agree with this to a certain extent but it appears that Honda, Kawasaki and Suzuki use 2 seperate mountain brackets connected to the swingarm however the Yamaha only uses one. After looking at some pictures it appears Yamaha have the poorest design.

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10/7/2020 7:20 AM

It would be just as bad if it didnt break right? The wheel would stop and probably break a sporcket.

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10/7/2020 7:25 AM

Skerby wrote:

It would be just as bad if it didnt break right? The wheel would stop and probably break a sporcket.

No I think I must clarify that no rock was ‘stuck’ in the chain block. A rock must just have knocked against it and ripped off the bracket at the welds. I wonder that people who have seen this on a KTM is it the chain block bolts breaking or the swingarm itself.

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10/7/2020 7:30 AM

Well, the KTM group of bikes do break the chain guide / guard mounts.

It's been a reasonably common thing since they introduced the cast swingarms. They tend to rip the bolts, most
notably, the forward one, right through the casting .

There's a whole bunch of companies that make strengtheners/ guards for the KTM, KTHuskies, and the coming KTGeeGees. They sure aren't producing them for no reason.

A good hit, a rock etc into the guide like your problem, will have a good chance at doing damage like yours on any bike. Probably the worst for this are CRFs over recent years, with many have only partial welds on the mounts, though I've seen, and (re) welded mounts on pretty much all brands, over the decades.

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10/7/2020 7:34 AM

Hmm now that I see how much of a problem this can cause I will definitely look into strengthening this part on my future bikes as I definitely don’t want to experience this issue mid-air ever again

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10/7/2020 7:36 AM

Happend on my 2018 CRF450......

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Washed up moto and enduro weekend warrior.

10/7/2020 7:51 AM

Thats why BPD makes these for offroad riders https://bulletproofdesigns.com/yamaha-swingarm-guard/

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KTM 350 XC-F

IG - @mattman122

10/7/2020 8:00 AM

Uncommon common problem. Off-road racers typically reinforce those tabs and run a beefier chain guide block (e.g. BRP or the like). I had the guide block tabs on my KX450 and CR450X reinforced with beefier welds.

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10/7/2020 8:01 AM

Bearuno wrote:

Well, the KTM group of bikes do break the chain guide / guard mounts.

It's been a reasonably common thing since they ...more

Would re-welding the bracket(s) to the swing arm, when new, to ensure good weld penetration, be a good idea? Would welding on the swing arm cause any weakening of the surrounding metal?

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10/7/2020 8:09 AM

Sorry that happened man, I would want an answer too. IMO the only thing more dangerous than riding over your head is riding scared/not confident in your equipment. That'll bite you quick. Heal up and get back out there!

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10/7/2020 8:35 AM

I have heard that the Yamaha chain block mounts are the weakest out of all the bikes.

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10/7/2020 8:55 AM

Bearuno wrote:

Well, the KTM group of bikes do break the chain guide / guard mounts.

It's been a reasonably common thing since they ...more

mxracer666 wrote:

Would re-welding the bracket(s) to the swing arm, when new, to ensure good weld penetration, be a good idea? Would welding on ...more

It depends on the original weld.

If it's a good, full length weld, there's not much point in adding to that weld.

A crap, partial weld, which is quite common, well, of course.

It's a murky area, with aluminium frames and swingarms, as to what actual Grande of aluminium is used. Many manufacturers, have their own variations on the metallurgy they use - proprietary, so to speak.

But, they mainly are 'blends' specifically developed to Not require artificial ageing / solution heat treatment after weldment. Mainly in 7000 series /H20 ( I may have that H number incorrect), that age back to specification in a short time. But then, there can be a wildly varying amount of grades of aluminium used on one single frame.

I've nearly always added reinforcing / addition tabs / brackets to my own swingarms, and to repairs I do for people, to ad in some geometrical reinforcement to the guide mount. And, to make up for HAZ zone 'damage' to the swingarm / repaired mounts / added bracing. I try to persuade owners to leave the Swingarm aside / unused for as long as they can ( which is usually the next bloody day, to allow for as much 'aging' as the materiaml allows.

And, I use / recomend the use of a full plastic guide / guard such as a TM, BRP, Acerbis, UFO, Polysport etc for some flexability to it, to both give the mounts an easier time, and to allow the guide to move back in line - bend the alloy cage, it stays bent, and can derail the chain, even if lightly tweaked. Many riders will just jettison the alloy part of the guide, if the design allows it, and the internal OEM plastic portion of the original set up is substantial enough - but, you are generally far better off to use aftermarket items, such as I listed, that are made
specifically to be used sans ally cage.

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10/7/2020 8:59 AM

It's 3 in the morning, I've been protoing a DH swingarm all bloody day and night, and am cross eyed, and didn't correct / finish off that post. And, the edit feature has 'disappeared', so, apologies if that post is a bit grammatically challenging, and not understandable......sick

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10/7/2020 9:12 AM

Not the first time I've seen the chain guide get ripped off at the welds like that on a yzf. Ever since they went to the newer style swingarm in 09. Doesn't take much to break it off I've seen a couple that looked like the welds barely hit the bracket mounts. Most just have it rewelded back on and have better welds done.

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10/7/2020 9:26 AM

I've seen all brands have chain guide troubles. My Kawasaki's were by far the worst, they are chain guide as much as rear tires. Waffled one on my 300XC in a boulder field, but nothing would have survived.

Think it is just one of those things...

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Tomac and/or Anderson for 2020.....

10/7/2020 9:57 AM
Edited Date/Time: 10/7/2020 10:18 AM

"Inherent Yamaha problem" is the funniest thtread title I've seen in a while...especially when it's NOT the brand that's had this problem the most...

Also, you might want to go look at the current mounting brackets on the other brands before being convinced that Yamaha is any different. I've had a few, on Kawasaki and Honda, that had welds that were incomplete.

There's even a few places that offer a servise to thoroughly re-weld and gussett the mounts on your swing-arm ...most notably on Hondas ...as they've done FOR YEARS...like JCR...
So, there's always that.

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10/7/2020 10:18 AM

TeamGreen wrote:

"Inherent Yamaha problem" is the funniest thtread title I've seen in a while...especially when it's NOT the brand that's had ...more

Well the bracket is clearly the problem, and it’s on a Yamaha. So it’s a Yamaha problem. If it wasn’t I wouldn’t be sitting here with 5 broken bones. I have now looked at other brands and yes I now see they are very similar however I’ve only been able to inspect my Yamaha and a KTM closely.

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10/7/2020 10:40 AM

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10/7/2020 10:42 AM

How many people actually strip the wheels out of their bikes and check for cracks on things like this?

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10/7/2020 10:59 AM

philG wrote:

How many people actually strip the wheels out of their bikes and check for cracks on things like this?

Hmm maybe not many I’d always check the frame etc. during washing or changing tyres (as a mountain biker I know the terrors of cracked frames). I think my wrong doing was assuming that bad welds could make it past inspection never thought anything of them while looking.

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10/7/2020 11:12 AM

philG wrote:

How many people actually strip the wheels out of their bikes and check for cracks on things like this?

r103 wrote:

Hmm maybe not many I’d always check the frame etc. during washing or changing tyres (as a mountain biker I know the terrors of ...more

But what makes you say its a bad weld? I cant see from the pictures, but if the weld has cracked, vibration, will set it on its way to fail.. that doesnt look like it had much of a hit to me.

But if you get a crack. and all welds have cracks, its how that propagate that causes a failure like this,

I have done post mortems on failed welds, and sectioned ones that havent failed yet, and when you see what they are like, these types of problems are not a surprise, but by the same token, you cant expect they will last forever.

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10/7/2020 11:22 AM

philG wrote:

But what makes you say its a bad weld? I cant see from the pictures, but if the weld has cracked, vibration, will set it on ...more

I never said it was a bad weld it was good to the best of my knowledge. In this case (although I’ll never know) I have to assume is was due to knock that it received and maybe chain block bolts>welds. It was such a sudden failure I’m sure I would of noticed any stress on my checks after changing wheel bearings not long ago. Plus it’s a two year old bike I’d think it should last this long.

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10/7/2020 11:23 AM

What happened to the 3rd bolt / hole? How did it manage to make it unscathed?

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