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Old 12-17-2010, 05:27 PM   #1
jimbee OP
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Location: Vancouver BC / Reno NV
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r100gs - cooked - overheated - dead?

Hello Everybody,

My little brother may have killed my dear R100GS. I keep track of receipts and know exactly how much stupid money I've spent on this bike, but I have no idea how many long nights, weekends, and "sick days" I've allocated to this needy mistress. In any case, something has happened and I'm not sure where to start to try to fix it.

Long story short: my little brother used the bike to try to jump start and then charge a tractor mower he was trying to sell. He started the bike and let it run in a stationary position until it started to smoke and eventually died. The choke was on and he explains that it was fast idling at about 4,000 rpm for about 45 minutes standing still before it died.

He didn't explain all this to me until the next day when I was unable to start the bike and noticed that there was a small silvery puddle on the ground beneath the bike. The starter was able to crank the motor, but the engine wouldn't start and the starter seemed to be struggling a little bit (it is Nippondenso starter and usually has little trouble).

I have had way too much on the go for the last few days to touch the bike, but I have noticed that it is now leaking oil from both cylinders at one or both sides of the heads and its also leaking from either the base of the cylinders or the pushrod tube seals (they were new and leakfree). The oil on the dipstick is very low and very very burnt!

So where do I start?

Do I pull the cylinders and see if the pistons seized and left a mark?

How do I know if the pistons seized and bent the piston rods and damaged the main crank bearings?

Less than 1,500 miles ago I had the heads reworked (new valve guides, springs, machined, etc.) and new piston rings. Does the leaking oil from the cylinders suggest the heads are now warped?

Am I even asking the right questions?

In any case, my purpose here is not just to rant, but to ask what is the prudent course of action and where should I begin? I am a shadetree mechanic, comfortable taking the cylinders off, changing the rear main seal, removing the transmission, etc., but when it comes to the deeper insides of the engine, I have not experience.

I guess the bigger questions is, should I start tearing into it and see what I can see (if there is anything to see), or is this one of those cases where you drop it off at a real shop and get a engine head to take a look? Money is tight, but I have A LOT invested in this ride and would hate to see it sit broken for too long.

Your adivice is appreciated.

Happy Ho! JB
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Old 12-17-2010, 05:33 PM   #2
Ben Carufel
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Quote:
Originally Posted by jimbee View Post
So where do I start?
Start by kicking your brother's ass.
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Old 12-17-2010, 05:34 PM   #3
OLD GREEN
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I would start by beating the shit out of your brother!
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Old 12-17-2010, 05:48 PM   #4
Steve G.
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Pretty clear the pistons have seized in the cylinders. The oil leaks are from the rubber seals being cooked. The crank should be ok if there was oil in it. But at this point, the engine and the oil have been overheated to such a degree, that, unless you ran full synthetic engine oil, it's time for a total rebuild, including the heads. If it were mine, this is exactly what I would do.
And rather than kill my brother, or even slap him around, I would make him financially responsible. And if he did not look after things, I would make his entire life a living hell.

Steve
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Old 12-17-2010, 05:49 PM   #5
fishkens
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Originally Posted by jimbee View Post
The choke was on and he explains that it was fast idling at about 4,000 rpm for about 45 minutes standing still before it died.

So where do I start?
First, enroll you little brother in a school for mechanical idiots. Then,

1 - Get a $2,000 deposit from him
2 - Change the oil, remove the filter, inspect the filter.
3 - Adjust the valves
4 - Crank the engine w/out spark plugs to get the oil circulating
4 - Do compression and leak down tests
5 - If it has decent compression, start it, warm it up and see if the oil pressure is 10 - 15 psi at idle
6 - If yes, take it for a ride and see what happens.

Report back.
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Old 12-17-2010, 07:44 PM   #6
anonny
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Take your brother and the bike to a reputable BMW repair depot and have your brother arrange to pay what it costs to bring the engine back to what it was before he hit the start button.
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Old 12-17-2010, 07:52 PM   #7
Tosh Togo
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Quote:
Originally Posted by Steve G. View Post
Pretty clear the pistons have seized in the cylinders. The oil leaks are from the rubber seals being cooked. The crank should be ok if there was oil in it. But at this point, the engine and the oil have been overheated to such a degree, that, unless you ran full synthetic engine oil, it's time for a total rebuild, including the heads. If it were mine, this is exactly what I would do.
And rather than kill my brother, or even slap him around, I would make him financially responsible. And if he did not look after things, I would make his entire life a living hell.

Steve
The OP rather clearly stated that it cranks in the same manner that it did before being fried, so that sorta rules out any chance that the "pistons have seized in the cylinders." The rings may be unhappy, and the pistons themselves probably have their own problems, but it ain't "seized".

Get in line behind his brother...
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Old 12-17-2010, 08:29 PM   #8
jimbee OP
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Quote:
Originally Posted by Tosh Togo View Post
The OP rather clearly stated that it cranks in the same manner that it did before being fried, so that sorta rules out any chance that the "pistons have seized in the cylinders." The rings may be unhappy, and the pistons themselves probably have their own problems, but it ain't "seized".

Get in line behind his brother...
Thanks All Much. Esp for understanding my emotional response (kill kill kill kiill)

Kicking my brother's ass isn't going to stop this from happening again (I HAVE THOUGHT ABOUT IT). Helping him get a clue about how things mechanical behave, or at least helping him realize that he knows so little that he should think twice before playing with machines could help maybe.

Dropping it off at Shail's, the local non dealer BMW shop, is an attractive idea, but my brother doesn't have a couple grand, and even if I do, I hate to write anyone such a blank cheque by dropping off a problem that I don't have a handle on myself.

So at this stage I'm just trying to figure out what the best and worst case scenarios are.

With this in mind, thanks Tosh Togo for inching back towards shedding some light into my black hole of understanding engine inards.

A few more specifics questions:

If a piston seizes, can it unseize after everything has cooled down (e.g. just becuase it can turn over now, is that conclusive eveidence that it never siezed and thus didn't cause deeper damage?

If the heads are warped, does that mean new heads or just that they need to be machined again?

If I do the labout and drop off an engine at a shop, what is a conservative guess on what a total rebuild should cost? This could be a good middle ground, where I get my brother to help with the labour and he learns in the process.

Fishkens, what would measring compression and leak down tell me? I assume that both would say something about the piston rings, but anything else as well?

Time for a scotch JB

PS - noticed there are a few other BC and other PNW posters here. I'm just moving back to BC and happy to know that there are other airheads this way.
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Old 12-17-2010, 08:32 PM   #9
Boojum
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Quote:
Originally Posted by Tosh Togo View Post
but it ain't "seized".

Get in line behind his brother...

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Old 12-17-2010, 08:46 PM   #10
Steve G.
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Quote:
Originally Posted by Tosh Togo View Post
The OP rather clearly stated that it cranks in the same manner that it did before being fried, so that sorta rules out any chance that the "pistons have seized in the cylinders." The rings may be unhappy, and the pistons themselves probably have their own problems, but it ain't "seized".

Get in line behind his brother...
kiss bobo, togo!
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Old 12-17-2010, 09:42 PM   #11
Beemerguru
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After the torture your brother (do a DNA test to be sure) inflicted , it's very likely it did seize up.

And when it cooled down, the piston gap came back so it would sorta turn over.

The potential killer part of this is that you have Nikasil barrels. Depending on how the pistons scraped along before they froze, you may have flaked off the coating and ruined the cylinders.

The only way to tell - and my recommendation - is drop the heads and pull the cylinders. Clean them up and look through the bore into a light. Look at ALL the cross hatching for small pockets..like inverted dimples. They may be in a circle around the bore where the skirt skidded to a halt. If the surface isn't perfectly consistent and smooth, the rings won't seat and it will ALWAYS burn oil..itwill run fine for a long while..but smoke like a destroyer smoke screen.

Also run your fingernail up and down the bore at a few places. If you feel a ridge line, your cooked.

Look at the pistons and see if you have any vertical grooves in the skirts. Run a new ring into the appropriate groove to see if the piston has collapsed. You might also tell if the ring doesn't rotate around the piston like it should.

Also look at the heads when you take the valve covers off. If the front towards the exhaust is a golden or dark brown, you've cooked the head and probably needs to be planed. Also look at the valves to make sure they're not cracked.

Good luck and tell us what you find..about your brother too.

If the heads are OK, you might get away with new pistons/cylinders, gaskets, bearings, etc. for around $5-700 depending on how good a negotiator your are. Add another $400 if the heads need a rebuild.
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Old 12-17-2010, 11:12 PM   #12
Padmei
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Jimbee will you be my big brother? Man you're one patient character.

If you strip it down could you please take lots of closeup pics of the internals so the experts can point out exact signs of abuse - Beemerguru gave some great instructions but actual diagrams would be priceless.

Best of luck
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Old 12-17-2010, 11:31 PM   #13
fishkens
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Fishkens, what would measring compression and leak down tell me? I assume that both would say something about the piston rings, but anything else as well?
Basic diagnostics w/out having to tear down the engine. Health of rings and valves. Leaking out the rings or the valves or both or none.

That said, these things are so easy to take apart that you could have the heads off in little more than the time it takes to do those tests. But I'm curious and like data points.

Quote:
Originally Posted by Beemerguru View Post
Also look at the heads when you take the valve covers off. If the front towards the exhaust is a golden or dark brown, you've cooked the head and probably needs to be planed. Also look at the valves to make sure they're not cracked.
BG: Is this discoloration really indicative of cooked heads? I've got that same discoloration and have heard of others with the pulse air system (whether or not it's still installed) having that as well.
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Old 12-18-2010, 05:55 AM   #14
mcma111
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Engine Work

Pull the heads and inspect the head gasket for leaks, distortion. No leaks = no distortion. Have the head surface checked for flatness. May need to be machined. Pull the cylinders and look at the pistons and the cylinder walls. Marks = no oil = bad. Pull the rods and look at the bearings and crank journals. Everything OK? Install new rod bearings. The main bearings will probably still be fine. Big ball bearings after all. Remove and inspect the oil filter. Metal or alloy = not good but probably from the piston/ cylinder sleeve's.

If the pistons or cylinders are bad I have the set from my 91 with 40k available. Still look fine. Just needs a clean up. Bolt on and go.

Total expense for the above? Rod bearings and rod bolts. Cylinder O'rings, head gaskets, head check fee, cylinders. Not as bad as it could of been.

Also your brother must buy all of the beer necessary for the above work to be preformed and stand by, watching you work in his underware, freezing his ass off. Some people have NO clue and I guess you have one. Sorry.
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Old 12-18-2010, 07:37 AM   #15
Jasper ST4
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With brothers like that you don't need enemies. 45 minutes?!!!! I wouldn't lend him anything again. If he's really that loopy he could have at least called you to ask. It's no small wonder why he doesn't have any extra money laying around.
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