Crank bearings

Riceburner · Mar 27, 2017

err - how easy are they to replace....

(ahem).

I think I've busted one or two over the weekend. :blast

Tazzing down the A303 to meet up with some other nutters for a 'big bikes off-roading day' the engine suddenly started making odd noises and then cut out forcing me to the side of the road and entailing an RAC trip.

The engine WILL run, both pistons are firing ok (as far as I can make out), but there's a horrible 'clatter' noise coming from the main body of the engine.

I initially hoped it was just a timing issue (jumped cam-chain for example), but I've looked at the time, rotated the engine slowly, and I've stuck an endoscope down each plug hole (all 4) to see if there's any damage - can't see any and it appears the timing is ok. The valves appear to be fine, there's no debris in the combustion chambers and the piston heads appear to be unmarked. (photos here : https://www.flickr.com/photos/rockburner/albums/72157678578465113 ). (I would have video'd the endoscope view, but for some reason the App has forgotten how to do video...)

Now, however - I think it may be a busted main crank bearing - but not sure how exactly to diagnose that without a full strip down.

If you listen to this video carefully, there's a 'clack' noise that occurs at (I think) roughly the same place on each rotation : https://vimeo.com/210057413 If someone else could confirm I'm hearing 'something' then at least I'll know I'm not going mad.

Next steps are to investigate repair or replacement options for the engine itself, (eg a 2nd hand engine from Motorworks). I'm in the somewhat enviable position of having a good 4 weeks of 'holiday' coming up in April (I just left my current job), but that kinda precludes anything majorly expensive.

Any thoughts/experiences on stripping an R1150 engine to bits?

flatdog · Mar 27, 2017

Put it in gear wth the plugs out and rotate the rear wheel, will give you/us a better idea on any noises. Rather than the spanner clatter I can hear.
If you can still hear something, then
- drain the oil and see if you have debris.

Cam chain tensioner upgraded?

Just considering cheap options first

flatdog · Mar 27, 2017

If it has run the hearings then this may be as a result of other failure and I certainly would expect the crank to be fucked too.
As you say a replacement may be the way forward.

Once you've confirmed it's fecked though :rob

Riceburner · Mar 27, 2017

flatdog said:
Put it in gear wth the plugs out and rotate the rear wheel, will give you/us a better idea on any noises. Rather than the spanner clatter I can hear.
If you can still hear something, then
- drain the oil and see if you have debris.

Cam chain tensioner upgraded?

Just considering cheap options first

flatdog said:
If it has run the hearings then this may be as a result of other failure and I certainly would expect the crank to be fucked too.
As you say a replacement may be the way forward.

Once you've confirmed it's fecked though

Thanks!

Yup - need to drop the oil and check the timing marks properly.

The LHS has the upgraded timing chain tensioner (did that years ago), but the RHS is original.

Steptoe · Mar 27, 2017

The clack you can hear at the same point on each revolution is simply the cam chain tensioner and is perfectly normal when turning an engine by hand . Have you checked the cam chain guides for breakages ?

(RIP) trickytree · Mar 27, 2017

So, you did indeed thrash it to within an inch of its life then

Smug · Mar 27, 2017

The oil pressure light will be on if any of the crankshaft bearings have gone.

Hay Ewe · Mar 27, 2017

Smug said:
The oil pressure light will be on if any of the crankshaft bearings have gone.

Only if the system works!

start with the simplest first
you may think its the crank, but as Steptoe says, could be the cam chain guides.
Check the oil for metalic debris, check the oil for fuzz, particles and chunks.
If you can identify the texture of the particles and chunks, that may give you a clue.

Gonna suck if you buy a new engine and it was only the cam chain guides

Smug · Mar 27, 2017

Hay Ewe said:
Only if the system works!

start with the simplest first
you may think its the crank, but as Steptoe says, could be the cam chain guides.
Check the oil for metalic debris, check the oil for fuzz, particles and chunks.
If you can identify the texture of the particles and chunks, that may give you a clue.

Gonna suck if you buy a new engine and it was only the cam chain guides

Oil light should be on when ignition is switched on and should go out when the engine starts. What could be simpler?

Santa-2512 · Mar 27, 2017

Crank bearing failure is normally a low end clonk that rises with engine speed.

Anything like this ?

https://www.youtube.com/watch?v=jb6UVNiNdoA

Mart

(RIP) trickytree · Mar 28, 2017

.....and I wouldn't have thought a crank bearing would have caused the engine to cut out.....front bearing causing hall sensor problems possibly....off with the front cover to check that.

Hay Ewe · Mar 28, 2017

Smug said:
Oil light should be on when ignition is switched on and should go out when the engine starts. What could be simpler?

you used the word 'should' many things should happen, but dont.
it has at least got me thinking that I need to check mine when I get home from this work trip, though I do a visual on the sight glass every few days

Smug · Mar 28, 2017

Correct. I did use the word should for a reason.

If the oil light doesn't come on when the ignition is switched on, then find out why. Bulb, wiring, oil pressure switch? What could be simpler?

If the oil light doesn't go out when the engine starts, then find out why. Oil pressure switch, no oil pressure, crankshaft bearings? What could be simpler?

Slipperyeel · Mar 28, 2017

Smug said:
Correct. I did use the word should for a reason.

If the oil light doesn't come on when the ignition is switched on, then find out why. Bulb, wiring, oil pressure switch? What could be simpler?

If the oil light doesn't go out when the engine starts, then find out why. Oil pressure switch, no oil pressure, crankshaft bearings? What could be simpler?

I need some help. Why would "...crankshaft bearings..." be on your list of things that cause the oil pressure lamp to stay on?

mikeyboy · Mar 28, 2017

Slipperyeel said:
I need some help. Why would "...crankshaft bearings..." be on your list of things that cause the oil pressure lamp to stay on?

The oil system is going to have a hard time building oil pressure if the crank bearings are shagged
Edit,the oil pump forces oil through the galleries to the bearings,because of the close tolerances the pressure of the oil rises to @ 60 psi,this allows the shell bearings to run/float on a film of oil ,if the clearance increases due to buggered shell bearings more oil will flood out through the bearing than the pump can supply and the pressure will drop,the warning lamp will prob illuminate a @ 15 psi,which in reality normally means damage will already have occurred

So if the light comes on due to lack of oil pressure ,the damage is already done!

mikeyboy · Mar 28, 2017

Here you go!
A set of big end bearings out of a 1200 that suffered oil starvation,
Low oil ,no oil or a cavitatiing oil pump due to a good Long wheelie,who knows,
But they're fucked and you can't put the metal back on.
The give away is a growling noise under load,most noticeable when pulling away

mikeyboy · Mar 28, 2017

And the mains

Slipperyeel · Mar 29, 2017

mikeyboy said:
The oil system is going to have a hard time building oil pressure if the crank bearings are shagged
Edit,the oil pump forces oil through the galleries to the bearings,because of the close tolerances the pressure of the oil rises to @ 60 psi,this allows the shell bearings to run/float on a film of oil ,if the clearance increases due to buggered shell bearings more oil will flood out through the bearing than the pump can supply and the pressure will drop,the warning lamp will prob illuminate a @ 15 psi,which in reality normally means damage will already have occurred

So if the light comes on due to lack of oil pressure ,the damage is already done!

Thanks Mikey. Your edit fills the picture for me. I think in my mind the light was a 'warning', hence me trying to understand how the light can 'warn' you of something that's already happened.

So in the case of shagged crank bearings, the light is a 'notification', not a warning

Going back to the op. If the bike was being hammered just before it cut-out, and it turns out that inners the crank bearings really have gone, oil starvation sounds like the culprit? Meaning not enough oil in the first place (or a substantial leak) I guess?

As already mentioned, it's not clear why it would cut-out, even if the bearings had gone? I wrecked a couple of engines in my youth and despite internal mechanical mayhem, they never cut out

Riceburner · Apr 26, 2017

Cheers all for the feedback.

I realised I hadn't updated this forum (so many fora, so little time!), so here's the news.

It's gone.

It turned out that the RHS big end bearing had 'disappeared', and the RHS upper cam-chain guide has also undergone a rapid unscheduled disassambly process.

I was turning over the options (full rebuild, replacement engine etc) when Motorworks mentioned that they'd be possibly interested in buying it. So I got a quote, which was quite surprising, and they picked the bike up last week.

Quite sad to see it go, but hopefully some of the parts will at least go to good homes in the future.

here's a vid of the big-end....

https://vimeo.com/211174752

Many thanks for all the advice and help in the past!

I've move on (temporarily?) to a 2000 955i Triumph Daytona.

Crank bearings

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