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Catastrophic engine failure pics

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stinkwheel
Bovine Proctologist



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PostPosted: 16:01 - 07 Apr 2019    Post subject: Catastrophic engine failure pics Reply with quote

So I was riding along on my old 350 bullet last weekend when it conked out. No funny noises, purring along happily one minute, total silence the next, just like I was coasting.

I pulled in and the engine turned over on the kickstart but no compression. Checked the tappets and the exhaust one was tight and stayed tight even with the adjuster backed right off.

Checked the plug and the end of it was missing and kind of hammered-looking.

Got recovered and put it in the naughtly corner until today.

Here's what I found!

https://lh3.googleusercontent.com/s0Yp56_2eHz6rUpxYesd0ZpN8JoXSVEOBOzbV_XO-JebAqfwzxq3XY-xULlqQ8VplCVHsPFvkdU8kfVxC_4hSIz7YnUeLBEd_UacPgr7ZR3WKbsiUgGMlONHFXrsROMDz4joPoPaAA=w1163-h872-no

https://lh3.googleusercontent.com/TDHjLpRJiOgGosWfqfIDz4FEhTajb9KFysr38vxRSnL6BBlKv91V7Swg_GGVFCrnWBfRKP5yTD2HXi0QYkR90TwD1DK8vF98ypC7RVjv-s9DuxoZf5SubIZU3P20IryEeX8YL-VCbQ=w1163-h872-no

Yes, that is the end of the exhaust valve. That also seems to be the only thing that's failed. No vertical play on the conrod. Piston is stiill attached, bore is clean, rocker gear is intact and mobile. I think the end must have just dropped off the valve, it shouldn't be mechanically possible for it to kiss the valve unless something else has also let-go.

I'm hoping the head will be recoverable with a bit of dremmeling to polish out the dings.

https://lh3.googleusercontent.com/Wow_z6YXPHbRYSOb284qTv7ndMORIMB_rLC6dCD7dTOwzA_qLNmc7JrrDVCPrjIyh9T45-1KEcRl8zO-tKYr4fi3uRbQ0BJU72FbAS3G1ZdLWYqnSygZknMeXcbNlfCegTGZ6-zyBA=w1163-h872-no

I'm off to split the engine now to see if I can find the rest of the piston. A relatively big lump of it was in the exhaust.
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I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.
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Sister Sledge
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PostPosted: 16:07 - 07 Apr 2019    Post subject: Reply with quote

Kin ell.
Not seen piston damage like that since I was 17 and riding stupidly tuned 2T 125s.

Does it mean a full engine split?
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MCN
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PostPosted: 16:09 - 07 Apr 2019    Post subject: Reply with quote

Buffing is out of the question in this case.

My 2p
Metal fatigoo in the valve stem. Repeated closing cycles possible caused it to become brittle and crack.

Edit: Shit quality pics BTW.. (Just sayin' Smile)
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stinkwheel
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PostPosted: 16:15 - 07 Apr 2019    Post subject: Reply with quote

Aye, new camera, not used to it yet. Literally the first pics I took with it.

I'm a tad miffed because it's a top-quality British made, plasma nitride treated valve, not an Indian jobby.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.
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stinkwheel
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PostPosted: 16:17 - 07 Apr 2019    Post subject: Reply with quote

Sister Sledge wrote:
Kin ell.
Not seen piston damage like that since I was 17 and riding stupidly tuned 2T 125s.

Does it mean a full engine split?


I 100% garauntee you never saw piston damage like that on a stupidly tuned 2t. Laughing

Yes, crank out. There are bits of piston unaccounted for. I'l do the mains while I'm in there. I'm pondering what to do with the crank. Wondering if a roller big end is in my future or if I'll stick with the floating bush (which seem to be perfectly ok). It's going to be spendy enough as it is.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.
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RhynoCZ
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PostPosted: 18:33 - 07 Apr 2019    Post subject: Reply with quote

That's just unlucky.
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Pete.
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PostPosted: 18:58 - 07 Apr 2019    Post subject: Reply with quote

2nd pic - edge of the valve looks burned away. I reckon it was either a little bent on the head and straightening each time it seated or got some debris stuck in the seat and bending a little each time. Edge got burned due to not seating properly and then the neck gave way perhaps from overheating or fatigue or a combination of both.

I had a GS550 head once with a slightly bent valve. Had the head off and rotating the cam you could visibly see the valve head straighten each time it seated.
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Nobby the Bastard
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PostPosted: 19:48 - 07 Apr 2019    Post subject: Reply with quote

Didn't you carry the tools to fix it with you?
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MCN
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PostPosted: 20:00 - 07 Apr 2019    Post subject: Reply with quote

Nobby the Bastard wrote:
Didn't you carry the tools to fix it with you?


There's a comprehensive tool kit in a roll-up under the seat of those bikes.
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RhynoCZ
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PostPosted: 20:11 - 07 Apr 2019    Post subject: Reply with quote

Nobby the Bastard wrote:
Didn't you carry the tools to fix it with you?

A replacement engine in the side-car, perhaps. Thinking
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stinkwheel
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PostPosted: 20:21 - 07 Apr 2019    Post subject: Reply with quote

Well, it's maybe as well this happened. Having split it, there is a distressing amount of play on the drive shaft (vertical and rotational). I think the key is the only thing that's been preventing it spinning-up. The rest of the crank assembly seems in good-order though.

That's not what caused this issue but it explains why the rotor randomly came loose earlier this year.

There are some mild planishing marks on the inner main bearing races too.

Probably get a service exchange crank, fit some European bearings and get it bored to suit the next size up forged piston. I'll see if the head is salvageable, I think it probably is.

Overall, it's not in too shoddy a shape for the mileage its done. The oil pump drive assembly looks pristine.

There are a couple of other jobs I've been wanting to do too. One is to fit a newer distributor housing with bearings instead of bushes (I got one in a box of bits). The other is to sort out the crankcase breathing by blocking the hole into the oil tank and enlarging/neatening the hole I drilled in the crankcase a few years back to allow it to vent to atmosphere. The way it's currently configured, it makes a respectable compressor.

@Pete. That would make sense. If a big lump of carbon got jammed in there, it might have applied a lateral force. I had to replace an exhaust valve previously because the edge appeared "nibbled" by carbon deposits. There is WAY less carbon about the place since I did the breather mod though.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.
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MCN
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PostPosted: 10:09 - 08 Apr 2019    Post subject: Reply with quote

A re-bore, new piston, rings and valves will improve the back pressure status.

Your not allowed to vent crankcase gasses freely into the atmosphere. You should duct the blow-by gasses through an activated carbon filter.
What about the environment? 🤣
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MarJay
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PostPosted: 10:41 - 08 Apr 2019    Post subject: Reply with quote

Looks a bit like my TT600 after it dropped a valve...
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stinkwheel
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PostPosted: 14:36 - 08 Apr 2019    Post subject: Reply with quote

MCN wrote:

Your not allowed to vent crankcase gasses freely into the atmosphere. You should duct the blow-by gasses through an activated carbon filter.
What about the environment? 🤣


What about crankcase liquids? Because it's a kind of snotty emulsion that comes out of it. Would that go through the carbon filter too?

Anyway, I sorted that problem out. The vent hose is attached the back of the rear mudguard so it doesn't make a mess all over my bike. Just don't put your windscreen wipers on if you're following me.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.
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MCN
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PostPosted: 16:21 - 08 Apr 2019    Post subject: Reply with quote

stinkwheel wrote:
MCN wrote:

Your not allowed to vent crankcase gasses freely into the atmosphere. You should duct the blow-by gasses through an activated carbon filter.
What about the environment? 🤣


What about crankcase liquids? Because it's a kind of snotty emulsion that comes out of it. Would that go through the carbon filter too?

Anyway, I sorted that problem out. The vent hose is attached the back of the rear mudguard so it doesn't make a mess all over my bike. Just don't put your windscreen wipers on if you're following me.


No problemo I have the Snotpal ordered.
It's only in development but I'm sure it will work.
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pepperami
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PostPosted: 20:06 - 08 Apr 2019    Post subject: Reply with quote

Well that’s just bad luck Evil or Very Mad , a detailed write up with plenty of pictures of the repair jobby please Thumbs Up

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Islander
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PostPosted: 20:41 - 08 Apr 2019    Post subject: Reply with quote

I've seen an example of this in a BMW airhead but they're a bit of a special case as the valve is two part (stainless tulip with a carbon steel stem welded together). IIRC it's only the exhaust valve that's made this way. Is it possible that RE use the same technology for their exhaust valves?
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stinkwheel
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PostPosted: 21:26 - 08 Apr 2019    Post subject: Reply with quote

Islander wrote:
I've seen an example of this in a BMW airhead but they're a bit of a special case as the valve is two part (stainless tulip with a carbon steel stem welded together). IIRC it's only the exhaust valve that's made this way. Is it possible that RE use the same technology for their exhaust valves?


Looking at the now extracted valve stem, it may well be. Either that or it has sheared VERY cleanly at a perfect 90 degrees to the stem. I'm going to show it all to my engineer pal tomorrow, he'll have a better idea about these things than me. Then I can make a list of what I need to buy to get it up and running again.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.
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ThunderGuts
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PostPosted: 21:29 - 08 Apr 2019    Post subject: Reply with quote

That’s pretty painful looking Sad hopefully repairable with a minimum of bits needed. At least it failed gently too and didn’t throw you off.
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flearider
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PostPosted: 22:10 - 08 Apr 2019    Post subject: Reply with quote

looked like my rs 125 from yrs ago .. just sold it as seen
what a mess ..
it blew at 90mph and locked up arse twinge but funny now
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MCN
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PostPosted: 22:34 - 08 Apr 2019    Post subject: Reply with quote

https://fpsdistribution.com/ae-explains-valve-breakage/

From the pic it looks like the surface of the break has been changed by the results of falling into the piston. Perhaps the other side on the stem holds some clues.
If it's a crack you can normally see the starting point and direction of the split. Maybe require microscopic inspection though and some sort of light filtration.
Someone trained in 'Failure Analysis' in machinery show be able to guess better.
Like the advice in the link, finding out the root cause is vital.
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Robby
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PostPosted: 08:21 - 09 Apr 2019    Post subject: Reply with quote

Seeing as it is an Enfield and you're always going on about how bad the machining can be on some of the OE parts, is it possible that the valve was OK but the valve guide is slightly out of line? That would give the same effect as a bent valve.
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stinkwheel
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PostPosted: 21:48 - 10 Apr 2019    Post subject: Reply with quote

From looking at the stem. It was (and is again) a 2-piece valve, friction welded. The weld has failed. It was also jammed up in the guide past where it was supposed to be (presumably because the spring pulled it up in there when the head came off.

However, having drifted it out, the stem is a very loose fit in the guide all the way along suggesting excessive wear on the guide. This could well have lead to wobbling.

The sheared surface of the stem is perfectly square across the axis of the valve and is blued suggesting extreme heat. It is totally smooth, no crystaline appearance.

I think Petes suggestion of repeated flex leading to fatigue fracture at the weld is pretty bang on. I suspect the wear on the guide preceeds the failure. So my story is it's probably carbon scoring of the valve seat/valve edge leading to blowpast, and excessive wear on the vlave seat. The resulting play/flex has caused a fatigue fracture of the stem at a stress point (where it tapers in at the weld).

In any case, going to attempt to repair it. My engineering guy reckons he can recut the seat in-situ and fit and ream a new guide. That should put everything back into line. The annoying thing is this was a fettled head so I can't blame Indian build quality. British made valves and guides and seats cut to suit.

What's bothering me now is if the damage to the inside of the head is too much. I've had a go at "buffing out" the damage to the alloy but I'm going to be left with a certain amount of pitting where the valve has hit the inside.

I've run old 2t heads looking WAY worse than that which had needle rollers hammered into them but is this going to cause major problems on a 4t? I suspect it'll all be full of carbon in fairly short order anyway. It's not a massively high performance engine and it'll be running 8:1 at an absolute maximum. I'd expect 15bhp absolute top-whack.

This took a LOT of elbow grease!
https://lh3.googleusercontent.com/JRHI7BVFKZD_zURey5uN5FqM9Yi1JR_xtx_cFX2uzxFbjUqPxu8m7_XD_N2_sqCM4Bd2RPiIQcA3ql3FKop3jmjWFv3WP_t2s8JcRhIrmxvEpK99L-3Eb8KsTgY_NBC4jeHMB2_2Vw=w1163-h872-no

In other news. The crank is scrap. For an entirely unrelated issue. The drive shaft is loose in the flywheel, only being prevented from spinning up by the woodroffe key so the shaft and flywheel are both suspect. You can't buy seperate flywheels. A shame because the (fail prone) floating bush big end is in good order despite having had 80k miles of thrashing.

So maybe as well this happened. A crank failure was imminent.

I've sourced a recon crank with a needle roller big end fitted. I'll keep hold of this one and keep my eye out for a scrap one on ebay. They are bolt together so if I can find one with a good drive side flywheel, I can assemble a spare.

Also managed to source an early 60's NOS 8:1 Accralite piston for less than the cost of a standard one. These do not come halfway sawn through behind the oil control lands and are not made of melted down rupees mixed with elephant poo. Win.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.
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Shaft
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PostPosted: 22:33 - 10 Apr 2019    Post subject: Reply with quote

I've seen worse than that on heads that haven't dropped a valve, you should see some of the shit that BL put together in the 70s!

I assume it's the chewed up seat on the right that's being recut?

Once that's done, I wouldn't worry about the rest of it, as you say, it's not exactly a high performance motor; if you spent the next month polishing it to perfection, I doubt you would notice the difference.
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Islander
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PostPosted: 22:55 - 10 Apr 2019    Post subject: Reply with quote

stinkwheel wrote:
From looking at the stem. It was (and is again) a 2-piece valve, friction welded. The weld has failed. It was also jammed up in the guide past where it was supposed to be (presumably because the spring pulled it up in there when the head came off.

However, having drifted it out, the stem is a very loose fit in the guide all the way along suggesting excessive wear on the guide. This could well have lead to wobbling.


That's a perfect description of the airhead exhaust valve failure mode. Thumbs Up

It looks like you're on top of the situation though (not that i'd have expected anything else Very Happy ). I'd say you've been lucky in a way, a catastrophic crankshaft failure could have caused a lot of expensive damage.
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