Broken Valve & Piston Damage

ferguscawley

ferguscawley

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On Sept 10, 14 of us set off from Ireland for an 8 day round trip of France & Spain. 100 miles into France, my mates 1100GS went pop. It was still running on one cyclinder (RH) but sounded very sick. We removed the LH spark plug on the roadside to find it had a huge gouge in it. Initial thoughts were a dropped valve. The bike was recovered and ferried home to my house. Last night, we began disassembly to see what exactly had happened. Upon removing the rocker cover, everything seemed fine. All valves appeared undamaged and in place and all 4 stems were visible.
We proceeded to remove the cylinder head and this is what we saw……
 

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It appears that the valve stem broke in half, the valve was sucked or driven into the cylinder head, rotated 180 degreees and was hit by the piston. The remainder of the valve stem then perforated the piston crown. (It was physically difficult to remove the remains of the valve from the piston).
 

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Cylinder head damage. Valve seat is actually OK. Apparent damage on valve seat is a piece of kitchen paper used to clean down the area prior to photographing.

It seeme that the head is salvagable – a polish and new valve should sort that.
Has anyone any experience of replacing a piston on a GS ?. From what I can see, there is a huge amount of work required to remove and disassemble engine to access the conrod and small end bearing.

Ferg
 

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is it not possible to undo the big end bolts & release the caps from the other side on oilheads?
 
Bloody hell, its amazing how the valve went thro the piston like that.
 
its amazing how the valve went thro the piston like that.
Click to expand...


not when you work out the piston speed in feet per second............

I'm surprised there wasn't more damage.

Its actually incredibly lucky it got jammed in the piston - imagine what the head,piston valves would look like if it was rattling around in there for a few seconds - carnage.

Very lucky - sort of
 
ferguscawley said:

Has anyone any experience of replacing a piston on a GS ?. From what I can see, there is a huge amount of work required to remove and disassemble engine to access the conrod and small end bearing.

Ferg
Click to expand...

Youve got the head off. Surely its not difficult to take the barrel off. You should not need to remove the conrod to get the piston off
 
Ouch!

With damage like that and the shock loadings that caused it, assuming the valve head punched through the piston crown, how much material has been fired into the crankcases? The conrod should be checked for bend and twist and the big end bearings replaced as they have probably been hammered out of round. With an offcentre impact point the piston will have skewed in the bore and there may be barrel/coating damage. Would you trust the rest of the valves are they from the same possibly dodgy batch?
just my two groats worth....
 
Den / Straypuss

I didn't initially realise there was a removable barrel-type arrangement on the GS until after I posted this morning. I thought that the barrel/crankcases were all one piece until I looked at the Haynes manual. It now looks like a relatively straightforward job. We have ordered 2 pistons (from an 1100S) , new gaskets and a valve from motorworks today so we should be able to repair the bike next week.

I will post pictures as we progress.

I am hoping that there is no damage to the bore. It looked fine when I gave it a preliminary look last night. As regards shrapnel in the crankcase - that remains to be seen. A good oil flush might/should look after that.

The plan is to fix the bike as economically as possible, and possibly sell it on shortly afterwards. It remains to be seen. (The bike is over 10 years old anyway and not worth a hell of a lot of money).

Thanks for all your replies.

Ferg
 
i'd want the con rod checked for straightness & changing the shells is a good idea.
 
missing piton part

That engine unfortunately has to be split,so all parts can be inspected for damage all cleaned and missing parts found,whats left of them who knows,but you have a lot of big moving parts in there,crankshaft/timing chains etc.I had the exact same thing happen to a citroen deisel once and that made a real mess.Have you drained your oil yet to see if it is full of bits of ali?.There is NO WAY you should put it back together with just an engine flush it's not worth the risk.Andy
 
Re: missing piton part

andy malton said:
That engine unfortunately has to be split,so all parts can be inspected for damage all cleaned and missing parts found,whats left of them who knows,but you have a lot of big moving parts in there,crankshaft/timing chains etc.I had the exact same thing happen to a citroen deisel once and that made a real mess.Have you drained your oil yet to see if it is full of bits of ali?.There is NO WAY you should put it back together with just an engine flush it's not worth the risk.Andy
Click to expand...

I was really really hoping someone wouldn't say that.......:tears
 
.

Sorry Furgus,only telling you like I see it.Did you drain the oil?I would be surprised if it's not got lots of silver in it.Andy
 
Andy

Haven't drained the oil yet. Will do so tomorrow. Its time for beers now :D
Thanks for all your input. Much appreciated.

Ferg
 
change all the bloody valves while its apart you tight sods. or you'll ruin your next holiday, if it gets that far .


:D :D :confused:
 
Steptoe said:
change all the bloody valves while its apart you tight sods. or you'll ruin your next holiday, if it gets that far .


:D :D :confused:
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From the hip Steps Wow :mcgun
:hapybnce:
 
Hi Furgus, I have had this happen to me twice before on my old R80GS, always on the near side cylinder. Once when the bike was just ticking over, and again at 90+ mph on the Autobahn at Munich. I actually rode the bike on one cylinder from Munich to Augsberg.
With the first one I only had to replace the piston and valve as the engine stopped dead. The head was dinged but usable.
The second was a bit of a mess and needed a head, barrel and piston. In both cases the exhaust valve had broken in the same as yours. Belive it or not BM valves used to have the head welded to the stem. I thought that they had stopped this but it looks like they havn't.
I never did do a complete stripdown to check the con rod or end shells and kept the bike for 18 years. The old airheads bottom end is totally bombproof.
I got all the seconhand parts from Motobins who recommended an alternative valve make. I think that they were made in Italy.
It used to be normal to replace the two exaust valves every 50000 miles as this was a known fault.
I get the feeling that the new oilhead is not built to the same standard, and if it was me I would do a complete stripdown.
Good luck and keep us informed.
 
ferguscawley said:
Den / Straypuss

The plan is to fix the bike as economically as possible, and possibly sell it on shortly afterwards. It remains to be seen. (The bike is over 10 years old anyway and not worth a hell of a lot of money).

Thanks for all your replies.

Ferg
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Bodge it. Use super glue, blue tack, whatever. Just stick it back together. Then advertise it:
a) Here, slightly under book - who knows, there may be some guy in Ireland looking for a 'bargain' ;) , or
b) Stick it on E-bay
 
Re: missing piton part

andy malton said:
I had the exact same thing happen to a citroen deisel once and that made a real mess
Click to expand...

when similar happens on a diesel the engine is usually totalled. con rods always bend.

petrol engines usually suffer far less damage.

if you're just going to pass it on, don't do too much work, but best not sell it here eh? :D
 
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