Rear suspension arm - Scary story.
 

Hi everyone,

I had an interesting trip to France in the summer of 2011 which resulted in having to replace a fractured suspension arm... The story follows...

The bike in question is a 2010 XT660Z (in fetching blue :icon_burnout[1]:) and had approximately 15000 miles on it, I had replaced chain and sprockets prior to the trip.

It was a lovely hot day typical of mid France in August and we were travelling on the motorway at about 80mph or so (legal in France). I was overtaking a lorry on a long uphill incline when without any warning I lost drive, rear wheel more or less instantly locking up for a couple of seconds, then one hell of a bang as the wheel began to turn again. After crapping myself I managed to freewheel between the lorries to the hard shoulder to take stock of the situation. No sign of the chain at all, Brucetopher1 (from this forum), who was following, said it just missed him as it flailed across the motorway and out of his sight... He towed me to the next service area which was only a couple of miles away so i could have a good look and arrange recovery.

Close inspection revealed the rear suspension arm badly damaged forward from where the axle spindle is located as well as chunks of alloy missing from the cush drive housing. The cast alloy bracket that supports the rear of the chain guard was also badly damaged. The photo below is of the arm after it was removed from the bike and the fracture had extended after being ridden. Once the wheel was removed the fracture opened up.

http://i1211.photobucket.com/albums/...h_1C9C31C0.jpg

Recovery was arranged and eventually a replacement chain was sourced and fitted. The French Yam dealers were not keen to let me ride the bike with the fractured arm but the engineer in me could see where the fracture was and that it would be mostly in compression if it was treated carefully. I off loaded much of my luggage to the rest of the guys and rode the bike gently for the rest of the trip. It got me home to Northern Ireland but the fracture could be seen extending as the days went by.

Once home I replaced the arm with a new one and fitted Stoic Bloke's chain guide mod, there should be no repeat.

So... What happened?

Initially I just assumed a broken chain was the cause, but... I now have a much clearer picture after inspecting the damage in detail and talking to those who were following me.

I had noticed at the fuel stop an hour before the chain let go that it was quite slack but hadn't worried too much about it, intending to adjust the chain at the end of the day, probably a mistake on my part. The temperature was low 30's so it was a hot day, and sustained motorway running at high speed would have caused the chain to be a lot warmer than usual too, and no doubt have expanded a bit more as well. As I was passing the lorries I had throttled off then accelerated as traffic in front cleared , this most likely caused the by now very slack chain to derail from the rear sprocket hence the loss of drive. It then caught on the bracket for the chain guard and snagged, bunching up between the cushdrive housing and the inner face of the suspension arm causing the wheel to lock and the pressure breaking the inner face of the arm and causing the damage to the cushdrive housing. The bearing in this was also damaged. Once the chain broke it was thrown clear. I would have loved to have seen the remains of the chain but it was impossible to retrieve.

Why do Yamaha not fit a chain guide to these motorcycles? It is such a glaringly obvious omission. The mod I have carried out was quite easy to do and should prevent any re-occurance. I am also watching the chain more closely on long motorway runs.

http://i1211.photobucket.com/albums/...h_18980C1F.jpg

I sincerely hope no one else has the experience I had, the cost of the repairs was bad enough but the outcome could have been a lot worse.

On the plus side, I can thoroughly recommend RAC European breakdown cover, they recovered me from the motorway (the french police initially do this but it was the same company that was sent by the police as the RAC use so they paid the recovery operator directly rather than me having to do it then claim it back). They arranged for onward transfer of the bike to a Yam dealer, I got a hire car for a couple of days, taxis to and from the hire car premises and there were several phone calls to check that everything was going ok for me and to keep me up to date with what was happening.

Next big trip for the Z is Nordkapp at the end of June, bring it on :002:

I just replaced my chain at 16k. The oe chain lasted well first then stretched very fast and was making a clanking noise now and then. Just fitted a did gold x ring chain - wow its like a new bike! Amazing what you get used to when it degrades slowly.

Jess thats a bit of bad luck.

I was lucky as a similar thing happened on my old XTR, had been out for a good 45min ride on country roads so was on and off the throttle alot and the chain was slightly more slack than standard but nothing overly bad. Came around a corner asked for the power and a massive racket. Lucky enough i was only doing about 30mph, free wheeled and pulled over straight away to find the chain had come off and was rolling over the hub of the wheel. No real damage apart from a few bits of paint on the chain stripped.

for me the moral of the story is, if yamaha want to build an proper overlander/offroader. build it properly - add a chain guide, even a dt50 from the early eightys had one!

hi irish guy, been in donegal enjoying the trails over the weekend. absolutely brilliant!

Glad you enjoyed them... did you find the 200 yard long "swimming pool?" Lol...

200 yard swimming pool? i certainly found long slurry pits!.:coolsmiley:

the sunday i was out on my exc doing peak to peak, will add photos later, else where, really should keep on topic

Yikes, that could have been nasty! Glad you came out the other end!

My OEM chain on my r only saw 10k before it starting giving way. It was ok but all of a sudden it just started stretching.

When i get my ten i will certainly be fitting a stoic bloke chain guide mod!

That's the thing though init? .... Yamaha haven't built an overlander/offroader. They have given us a bike with firm foundations to do either.

Overlanders are a funny bunch, and you would be hard pushed to find two riders who would want the same thing from a bike. But you only need to look at how straightforward it is (with a little engineering skill) to modify these bikes to suit individual needs. That's the strength.

I've seen a chain come off a bike (in front of me) once, it run out the back and slid down the road like a snake, nice and neat, no damage to anyone/thing. I've seen the aftermath (in the flesh) on another occasion, and the chain destroyed the engine case on it's way out. Now I have seen a third, and it destroyed the swing arm, but this sounds less like a broken chain and more like a derailment. However you look at it, had the chain been tight, it couldn't de-rail (unless there was something else wrong with the chain at that moment), as the chain wasn't recovered it's all really just theory. My point here, is that, certainly in my experience, chains are very unpredictable when they 'go', at speed with load this becomes even more unpredictable.

Theorising here a little, but what if a chain snapped between the guide and the sprocket (however unlikely)? then it's possible the same guide could momentarily grip the chain, leaving a flailing steel chain whipping around at the back end of the bike. It's all conjecture of course, just trying to point out that modifications could make things worse. We will never know why Yamaha decided to avoid fitting a chain guide, could be cost, could be they just forgot, could be aesthetics or it could be that they had some data suggesting chain guides create more potential problems than they fix? It would be nice to know though.

A few months ago, my own chain stretched, probably enough to do the same as as happened here, I noticed it because it was 'banging' on the top of the swing arm during throttle-back. I stopped and adjusted it. As the chain is approaching 30K, I think I'm pushing my luck somewhat now.

Chain guides have a specific purpose, I'm not sure they suit everyone. On the road, they provide a sense of security, but as we humans go, this means we just push things a little more, maybe carry out less adjustment. On the other side, a dirty chain guide is going to wear a chain - I have seen this, especially with a spilt link fitted....... As I say, we all have different needs/wants and these bikes provide one of the best platforms to build the bike of our needs/wants.

Nearly everything can be modified on these bikes, where they really fall down is the Stator, it just doesn't give enough Uuumph! And there isn't much we can do about that. But that's another discussion.

Like Keith though, I pay close attention to my chain each ride, Scottoiler and weekly maintenance on top. Between that and the rubber, the two (or rather three!) most important checks on the bike.

You were very lucky with the traffic, and good skills in bringing the bike home all alive. Motorcycling is a dangerous business, every day we survive it is a bonus!

Blimey you were really lucky as anything could have happened. I once had my rear wheel of my CBR1000 block at about 70mph on the motorway in the middle lane, and how on earth I was not taken out by another vehicle as I made my way across to the hard shoulder I will never know. And good point about the chain guide, would that have helped?? The drive chain on my 07 XTX did 15.000km and is still good, and I now have 6,000km on my 11 XTX and so far I have only needed to lube it, which I do every 2 weeks or so. I have never fitted a Scott Oiler, are they a good idea??

Assuming the chain is about 1.5m long, you'd need a temperature rise of about 55 degC to make it 1mm longer.


Pedantry aside, I'm with Gulgo on this one. Not enough information to say that it was the lack of chain guide that caused the problem.


Glad you came out of it unscathed!

Well done, good save.

Thanks for posting as it reminded me to check and adjust my chain. I clean it regually but occaisionally fall into the trap of my own lazyness of thinking that 'I will do it next time' and as most of my everyday trips are short I convince myself that this is ok but know it not to be. Thai serves as a good reminder regardless of the reason.

I think the chain adjustment procedure on the tenere is partly to blame. Having to set it with the bike upright and not on a stand is daft. That is the official way of setting it but without two people its near impossible so I think it gets left too long.
I know someone took off the linkage to work out ideal adjustment. They published the 'on centre stand' gap ie swingarm to chain gap - anyone remember what it was ?

unlucky but lucky ..... the regina chain itted to mine as o/e equipment was very poor quality
im wondering if yours was the same make .. im suspecting it may be

Pedantry aside, I'm with Gulgo on this one. Not enough information to say that it was the lack of chain guide that caused the problem.

hi, I have never suggested the lack of chain guide caused the problem, chains like any component can go wrong and fail. it really is quite easy to derail a chain while trailing and cause damage, so why not fit one?.
you wear body armour, jacket, boots, etc. you hope not to test how well they work?.
if you's think ooh.. snake oil, no one says you have to follow suit

ciao

I use the "Two finger " method. While the bike is on the sidestand, Put two fingers between the chain and the fattest part of the swingarm... It should be possible but a tight fit... Your chain is good :-)

Another easy test.. Tilt the bike upright, the chain should just lift of the chain roller :-)

My 2c

I never said you had, or that chain guides aren't useful in some circumstances - particularly on the dirt. You may well find me as a customer at some point ;)

All I said is that I don't see a particularly compelling explanation as to why it would have prevented this particular incident.

My user manual says to set it on the sidestand.

I've been around bikes all my working life and do a large annual mileage on several bikes, 25k to 30k miles a year on average, (I ride as part of my full-time job, I run several group tours each year as a part time occupation and do a lot of personal stuff too). I've lost chains before but nothing as dramatic as this... I have a Scottoiler fitted.

My preference is to run chains a little on the slack side as I'm a big lad with a healthy appetite and often the manufacturers advice (not just Yamaha), on chain adjustment, particularly on trail bikes, leaves it tight when the full range of suspension travel is used.

I'm not saying the lack of chain guide would have prevented a chain failing for some reasons, but it would have definitely prevented a derail from the rear sprocket in this case if that is what did cause this incident.

For me, and the type of riding I do, the addition of a chain guide definitely adds a bit of reassurance. It's great to see other peoples views on the matter. My main reason for putting the details here is to share the experience and see what, if any, lessons can be learnt. I always try to analyze a mishap whether it be a riding mistake or mechanical failure to see what i could have done differently either before or during the incident to have had a more satisfactory outcome.

Almost all other manufacturers of trail bikes do fit chain guides though...

Cheers.

I'm with stoicbloke and irishguy on this one. On a bike that requires substantial chain slack (50-60mm) it is bordering on negligent not to fit a chain guide. I also ride for a living, and believe me, a chain guide is essential imo, paricularly offroad.
I realise that the above event happened on-road, and so did the only major chain break I've had (curiously on a 96 Tenere). That aside, in general any bike running a lot of slack should have this safety net. Again imo, of course.
I am relieved that irishguy is ok. Good riding, mate.

Yip..two finger method for me too....has worked so far and is easy to do....

Just say'in like...

:)

.

i aggree the chain guide could stop derailment ..preventing derailment could prvent snapping ,,i have one fitted but mostly for ruts and mud

ive had a bad chain on my xt ...mostly caused by a very quick wearing front sprocket in maroc ..

bad cush drive is not going to help a vunerable chain either .. ..so keep an eye on that

for what its worth ive found ek mvxz chain to be very robust ..but keep an eye on that front sprocket

just wonderiong how it looked irish ..the front sprocket i mean ...
we live we learn

Hmm thinking of adding a chain guide.. I have still a fresh memory of the only time i have snapped a chain
http://majland.org/blog/wp-content/u...varivalby1.jpg

The chain was only 4000km old and it broke by where it was put together with the clips. More pictures on: http://majland.org/blog/?p=220

I've only ridden endless chains since then. What does it take to fit and endless chain to a xt660z ? On my xtz750 it involves drining the oil and taking of the rear suspension arm ...

i really dont think you need to go to that extream ...just use a rivet link with the correct nm ,,,its surprisingly low to rivet a chain ..overdoing it causes tight spot s

Chains with hollow pins like DID are very easy to rivet with the right tool. But for peace of mind an endless one might be just a bit better... And you have to grease the rear swingarm once in a while anyway :)

The DID rivet links I've used only allow the pressed-on plate to go so far. So you can't really overdo the tension. Also, rough though you might think it is, I've always used a pair of uneven weight hammers to rivet the link. No problems after many years and km. Imo a good chain isn't too fussy as long as it isn't run too tight. That's when they tend to break, or pop the clip if one is fitted. A worn clip is also a bit risky!

In my experience: Yes. Very much so.

Easily doubles the life of a chain and reduces adjustments because the Scottoiler oils it AND keeps it clean.

I took my ratty old Triumph Tiger to Istanbul by way of Holland, Germany, Austria, Hungary, Slovakia (wrong turning), Romania (Transfagaran), Bulgaria, Turkey, Greece, Serbia, Montenegro, Bosnia, Croatia, Slovenia, Italy (Stella Alpina), France - total of 5000 miles in a fortnight.

Didn't need to adjust the chain once - in fact a thousand miles later I still hadn't. The chain was adjusted when I replaced the rear tyre, not because it needed it.