***STICKIED***


Right then, I have trimmed and stickied this thread as I feel it is *that* important ... frame cracks are bad news and a bike with a crack should not be ridden until fixed ... luckily the F1 has a steel frame and that means the bike is eminently fixable, so post your own experiences and pictures of your cracked frames here and how you got them fixed, results, mileage etc ... discussion regarding this whole issue is welcome but please try to avoid the chit/chat non relevant stuff or I just have to come back with my pruning sheers ..lol


As already mentioned in this and many other threads, it's almost impossible to conclusively prove the reason for these cracks, we have anything from high frequency vibration to stunting to bad design ... my own opinion is a combination of age and fatigue, fatigue will always get the weak point first ... I notice the cracks are near a weld and this in itself can be another reason ... when metal is heated up and rapidly cooled as in welding it can harden and become brittle, with time and riding, even just everyday bumps in the road let alone wheelies then these points can fracture ... once this has occured it can only get worse and needs immediate attention.

A professionally welded up frame will be fine and probably cause no further trouble ... if you just borrowed your mates mig welder and splattered a load of snot on it without much preparation then maybe not so good ...



Jules

 

This is a good subject and we've had a number of theories as to why the frames are cracking - I think we should be thankful to have had the issue brought to our attention - never mind what the cause is, the nett result could have been a nasty accident or worse if the matter was allowed to be left unexplored.
And it's always wise to drill a small hole at the end of any crack - stops it travelling.
I think this kind of thread will save lives - excellent
Quote Hurricane_87
but i figured better than starting a new anti censorship thread people arent always gonna get along.....this is life.........dont worry, this will never happen again
That would not be in the interests of this discussion, would it....................

And yes, it's appropriate for a Mod to keep a post on topic ...............
It's one of the responsibilities................

 

well, relevant to this, i noticed around 6,000 rpm my bars hum pretty good, thought there might have been something wrong, from what i gathered it seems normal, i usually cruise around between 3 and 4 passing this "humming" zone briefly...today i was out in traffic....held a shift off a lil bit and noticed between 5,000 and 6,000 my grips were rumbling pretty good....so apparently this is normal with these bikes? no way to smooth it out? better grips? or just not haning around 5-6k rpm?

 

I've had my Hurricane since new in 87. It has had that buzzy zone since then so I'm calling it normal for the model. I've tried a one tooth smaller countershaft sprocket to boost the rpm by 500 at any given road speed...it was a bandaid solution. I just wore out chain and sprocket sets faster. Now I just run in a lower gear if my speed falls in the buzzy zone.
I have considered taking the time to balance and blueprint the engine to see if that would smooth it out, but I haven't got there yet. Unlike its big brother the 600 doesn't run a balance shaft.
If you have access to an old copy of CYCLE magazine from Aug 87 you can read about how they bought two identical bikes and had different performance, handling and mechanical feel. One was buzzier out of the box but it also dynoed 2 hp and 2 ft/lbs stronger.

 

Shadow's suggestion of drilling a crack is a sound investment.

It does create crack retention, retarding growth its exactly why helicopters and planes contain millions of rivets (most applied by hand) to this day, as each one will stop the growth of a crack - it's a decades old practice which can't be beaten.

One recommendation though - keep the hole as small as possible, larger than the crack width but only remove as little material as possible thereby avoiding other issues including large hoop stresses and providing a channel for moisture to cause corrosion somewhere else.

I've been in working in Canada for the past week (a lot seems to of happened on this post recently) and i'm so glad our frames are made of steel and no idiot has decided to make them out of Aluminium-Lithium as we would all be in a world of hurt. You'd be surprised how much a helicopter and a motorbike have in common (bar a few slight differences, rotor blades, bad paint jobs and various armaments - but there are similarities).

I would like to add that as agreed this thread is for preserving safety when riding but if we unfortunately have to sell our bikes for whatever reason, we all owe a duty of care to the next rider as well so if you do make a repair/modification let the next owner know what you did and why or what they need to do, because that's what bikers do - we look out for each other.

 

ive got one too on lh side of bike identical to your pics how safe is 2 up like this have to do 180 miles in two days

 

Hi,
I am fairly new to this forum,cbr 600 ownership but I am far from new to locating and dealing with cracks in steel structures!

I have been looking for and dealing with structural cracks on offshore oil platforms for about 20 years now.

The anwser is that no structural crack is safe unless delt with correctly.

The first thing is the crack you can see is not the full extent of the damage.

We use various methods to find the size/magnitude of visual cracks well beyond the scope of this posting ,however
Dye penetrant is probably the easiest and cheapest one to use if you wanted to find the true extent of the damage your self.

I can pretty much gaurantee the crack(s) will be about twice as long as you can see at the moment prehaps more and will grow/propergate if no remidial action is taken.
Cracks in steel structures grow and the more stress you put the structure under eg heat changes, g loading ,vibration etc the more it will grow.

Get a small sheet of thin plastic say about half the thickness of a credit card and put a small nick in one side in the middle of the sheet.Then start flexing it like a Rolf Harris wobble board!

You will see a stress line/crack appear across the centre of the sheet and eventually the sheet will break in two.

That is what will happen to your fame if you do nothing!

It will probably fail at high stress ie when you are accelerating or braking hard most probably braking ie the worst possibble moment!

It is not a linear process and will happen very suddenly when a critical point is past in the failure sequence.

Small cracks like this have collapsed whole offshore oil platforms and brought airliners down in the past with little or no warning!

Please google non destructive testing if you want to now more about this subject.

Sorry to be the bearer of bad news but if you do something now the frame can be made good and safe again
.
I personally would not ride a bike knowingly with a cracked frame.

BTW the drilling a hole in the crack method is only a short term partial solution that slows things down a bit for a while if you are lucky.
Bear in mind if you checked the crack with ndt equipment it would already be past the point you drilled it at but is slightly better than doing nothing.

This information is my own opinion and is supplied for general interest only.
Cheers all.

 

The frames are relatively easy to weld. My first attempt, I stripped it down to the bare frame and welded it. My second frame repair(different bike) I left the engine in. I would not recommend riding the bike without repairing the frame, especially if you have a passenger.
I have never seen a catastophic failure yet, but you don't want to be the first!

 

mines goy one on lh side is it only lh side thats affected