Can this Piston be Salvaged?

[Ken H.]

Can this piston be salvaged? A rhetorical question obviously. My questions go beyond the piston though.

 

 

The short story – Last week I hard low sided our R1200GS. Full slam down on the left side as I just started to crank into a hard lean around a street corner last frosty Wednesday morning. (Other than a jammed thumb and a few sore spots, I’m OK. ATGATT.)

 

So the vale cover is smashed into the valve train, the head has a big hunk out of it and one intake valves leaks, the cylinder is cracked through near where it enters the block, and well, the piston didn’t fair so well either. The deflection that happened when the bike hit the ground was so great it even sheared off the alignment dowel pins between the cylinder and the head. Interestingly, the long head bolts seem to have survived though.

 

Ugh, what a mess.

 

Plus of course a whole long list of non-engine parts on that side are trashed.

 

My questions are these:

 

1) The piston to connecting rod wrist pin and its bearing in the connecting rod, as well as the connecting rod itself appear visually fine. But how likely is it that there is damage at the connecting rod to crankshaft bearing? And how can I be sure?

 

2) The service manual speaks of the left side and right side pistons must be within 10 grams in weight of each other. The parts list shows five different weight ranges for the left piston:

 

- 563 - 570 G

- 563 - 573 G

+ - 568 - 578 G

+ 573 - 583 G

+ 576 - 583 G

 

For one thing the weight range's overlaps and "+ -" nomenclature are kind of strange. Can anybody explain these ranges?

 

5) The manual says to remove the opposite side piston and weight it to find a match. How critical is this? I’m loath to pull the right side apart too, but will if I have to I guess.

 

6) If I do have to pull the right side, should I put new rings in when reassembling? If I do, should the right side (being reused) cylinder be honed first?

 

7) Should a new BMW left side cylinder be honed prior to installation of the piston?

 

8) What cylinder to block sealant to use during reassembly? Presuming I ever get to that point. )

 

9) Anything else to look for from such a hit? Visually the block itself appears fine.

 

At least it's November and riding season is winding down instead of it being April.

 

Thanks for any insights.

[bimmers]

how many miles ar eon the bike? That would determine if you will have to (or should) have a go at both sides. To get them to same diameter and even.

The rods do take some abuse but I would suggest you at least pull them all out and if you have enough miles then it is worthwhile to do the bearings t the same time.

YOu obviously are not insured for this, otherwise just leave it to the dealer to figure out.

 

good luck even if I cannot help you more than (common sense)

 

h

[Mr. Frank]

For even more input from a diverse and savvy audience, I'd suggest you post this to the IBMWR list.

[smiller]

Besides my condolences a couple of thoughts Ken...

 

I guess there's two ways to go about it: the total 'do it right' way which would essentially entail a major tear down and rebuild, or the 'use logic and hope' approach. In the latter vein... short of a teardown I'm not sure that you can be certain about whether the bearing(s) were damaged or not, and since you can assume that the pistons were matched at the factory if you replace the damaged piston with one of a similar weight you should probably be pretty close. No doubt there will be disagreement but I'd be pretty tempted to just replace the damaged parts and ride it away. If there was any internal damage and you subsequently have to tear into it then you won't have lost much as the work will be near the same either way. I think the odds are enough on your side as to be worth the gamble.

 

If you do decide to tear into the good side I see no reason to replace the rings or re-hone the good cylinder. As for the new cylinder, I would think that it would come ready-to-install (p-honed) but that's a question for your parts guy I guess.

 

Really sorry to hear about this...

[BeemerLover]

Ken,

 

Turnabout is fair play!

 

Thank you for your help with the Hyperlites today.

 

I've worked on "old car" V-8 engines for years. Seth has it right - you should be conservative in your approach. Otherwise it will never run right and you you will be taking it apart to solve problems in the future. That engine suffered a lot of trauma and you really do not know what is right and wrong. A bent crank can visually look perfect. A connecting rod can look perfect but have hairline cracks and you would never know.

 

Good Luck, Gael

[bobbybob]

What beemerlover said and more: a blow that severe could crack the case, even though you can't see it. You might want to have it magna-fluxed, or use some dye penetrant.

[Tony_K]

Wow! Bummer, so sorry that happened. I know the feeling and it aint good.

 

Getting a pistion weight match isn't hard but you do need the other piston out to do it. Of course you can skirt this and just hope that the replacement is within reason of the other.

 

But as Gael had said you may want to split the case... ugh I know that is the last thing anyone wants to do but if the slam was that hard and it was on the top of the stroke (as it appears) that can transfer a lot of force to the crank and bearings.

 

May I suggest a complete engine swap that may save you time and money in the end?

 

Again glad YOU are ok!

[ShovelStrokeEd]

Damn, Ken,

You do pull some beauties. Glad you're OK buddy and doubly glad Donna wasn't aboard as well.

 

Given the bang that thing took, I wouldn't leave the rod in there and would have some concerns about the crank as well as the crank case. Takes a hell of a whack to shear off those cylinder base dowels.

 

If it were my bike, I'd look into a short engine assembly from BMW. That and a new head along with the rest of the parts salvaged from the old engine and you'll be back in business. After a whole bunch of work, of course.

 

What has your insurance company to say. Might just be better to total the bike if you are covered, or look for a wrecked bike with no real damage to the motor and purchase that.

[smiller]

That engine suffered a lot of trauma and you really do not know what is right and wrong. A bent crank can visually look perfect. A connecting rod can look perfect but have hairline cracks and you would never know.

All true but I think you misunderstood my opinion. If you are going to worry about all the potential issues then you will end up throwing so much money at the thing that you might be (financially) better off by looking for a good salvage engine. I haven't seen the damage but if it were me I think I'd be temped to just fix what is obviously broke and go for it. Considering that the odds are in your favor (I think) and the alternative total tear-down and inspection would be enormously time-consuming I think it's a reasonable gamble. Replacing just the bad jug, piston, and head isn't so much labor that you will have lost much in the unlikely event that you do end up having to really tear into it later.

[Stan Walker]

WOW!!!

 

I'm impressed big time!!! I didn't know you could do that just by dropping the bike. Maybe the hexheads aren't as tough as the earlier oilheads?

 

Very glad your OK.

 

My gut level feeling is that you stopped the engine at ??? rpm in the space of a few degrees of rotation. I would suggest the the main bearing, rod bearing, rod, wrist pin, as well as the piston are all suspect on the failing side. I would inspect the crank, engine casing, etc. for additional damage.

 

It might be cheaper, and surely will be easier to drop in a short block.

 

Paul Glaves is the only one I know who has ever been that far into an Oilhead engine. He rebuilt Voni's RS when it fragged a cam chain guide many years ago. You might ask him for an opinion.

 

Stan

[smiller]

I didn't know you could do that just by dropping the bike.

Yeah, that's a good point and I was gonna say...

 

I don't think I've ever heard of actual engine damage of the type you describe in any other oilhead slow-speed lowside. Were there any unusual circumstances?

[Don_Eilenberger]

I would be looking for a new/used engine. If you have insurance - now is the time to use it..

 

As far as honing a replacement cylinder - nope. It's Nikasil coated, and unless you're using diamond hones nothing is going to touch it anyway. They come from the factory ready for use.. and even a used one really can't be honed (or bored or much at all..) Used cylinders with > 100k miles on them typically still exhibit the factory cross-hatch.

[Ken H.]

how many miles are on the bike?

28K

[Ken H.]

if you replace the damaged piston with one of a similar weight

The thing is, I'm not sure how I'm going to figure out the weight of the damaged one? Too much of it is missing.

[SageRider]

Ken,

I can't contribute to your questions, but I'm sure glad you're OK!

[Ken H.]

that you stopped the engine at ??? rpm in the space of a few degrees of rotation. I

The engine was at idle. I had pulled the clutch to glide down a long, straight downhill exit ramp and make a sharp left at a T intersection at the bottom of the ramp.

 

My feeling based on the camshaft position when I took it apart is that side was on the intake stroke when it was stopped. The crack and gouge in cylinder is toward the lower portion of the stroke. This wasn't a valve crash, even though one intake valve now leaks solvent by even when closed. Not the one across from the piston damage. There is no sign of hard contact with the valves themselves or the combustion side of the head. It wasn't until I hit the starter just to see what would happen after I got the valve cover off, that it piled debris up against the head and locked.

[smiller]

The thing is, I'm not sure how I'm going to figure out the weight of the damaged one? Too much of it is missing.

OEM pistons are often imprinted with a weight grade or marking of some kind, which is what I was assuming. If not, and the broken-off piece is not in a single (weighable) chunk then yeah, bit of a problem there...

[SHIMHEAD]

The thing is, I'm not sure how I'm going to figure out the weight of the damaged one? Too much of it is missing.

Weigh the remaining piston (less the rings), then remove a similar section of the material and weigh it again. That should give you a very close estimate of the missing piece, double that amount and add to the original weight of the damaged piston and you should be close enough to select the correct piston. What happened to the missing piece? Please post more pics of the engine, I'm sure we are all curious about the other damage.

[Ken H.]

What has your insurance company to say. Might just be better to total the bike if you are covered,

I only carry liability on the bike. So it's fix it out of my pocket, or no bike.

[Timmer]

Can you get a closeup photo of the area where the cylinder is cracked through near where it enters the block? And also the block area.

 

Sorry to hear about your mishap. Glad that you're ok...well at least as ok as you can be under these circumstances anyway.

[Ken H.]

Were there any unusual circumstances?

The bike ended up with that side against a curb. The front exhaust pipe, right where it curves down out of the head on that side is crushed, so a lateral hit of the pipe against the concrete curb might be what did the head & cylinder damage rather than the side fall.

 

I didn't see it hit, I was rather occupied at the time.

[Ken H.]

OEM pistons are often imprinted with a weight grade or marking of some kind, which is what I was assuming.

According to the service manual they are, "...on the crown, which are no longer visible once the engine has been ran." Brilliant.

[Ken H.]

Weigh the remaining piston (less the rings), then remove a similar section of the material and weigh it again.

Now there's a clever idea! Thanks, I'll do just that if I decide against a total tear down.

What happened to the missing piece?

I didn't read about the whole piston weights thing until I had already cleaned up most of the mess. Suppose I could still go pick all the pieces out of the garbage...

 

Think this whole piston weight matching thing is that critical? Apparently it's all new to the hexheads. The oilheads didn't differentiate that I know of.

[smiller]

The oilheads didn't differentiate that I know of.

The oilhead service manuals also state that pistons should be weight matched.

 

As far as how important... probably not critical as long as they are reasonably close but a better match may result in a smoother-running engine.

 

Does the damaged piston have no weight class markings on it?

[big-t]

Ken, sorry to hear about your mishap.

 

It sounds like you could easily install a new jug,piston and head and drive away,but one aspect of that repair you will have to deal with is going to be a mental one.

 

Everytime a little vibration or noise shows up,you will be wondering is the rod coming loose,or is going to blow?? Not particularly comforting feeling when your 2k away from home

 

Given your description of the impact and damage,I would be concerned with the rod alignment and the relationship between the crank and cylinder alignment,thats something that might not show up for several thousand miles.

 

 

 

Good luck.

[Ken H.]

Can you get a closeup photo of the area where the cylinder is cracked through near where it enters the block? And also the block area.

It's tough spot to photograph down inside the bore, but here's one from the head side:

 

 

And from the block side:

 

 

And anouther spot where the cylinder is cracked:

 

 

Here's the surface of the block:

 

 

And of the head. The marks at 5:30 are from debrie pushed up against the head when I tried to turn it over. The valves look untouched but the upper right one (intake) one in the photo lets sovlent poured into the intake runner through. I haven't pulled the valves yet as I lent my valve spring compressor tool to someone awhile ago and I've got to get it back.

 

[Ken H.]

Does the damaged piston have no weight class markings on it?

Nope. According to the service manual they are, "...on the crown, and are no longer visible once the engine has been ran."

[smiller]

"...on the crown, and are no longer visible once the engine has been ran."

Crap.

[StuGotz]

I am not a Tech moderator, but FWIW:

 

I would think your options are limited to three here:

 

1. Trash the bike, buy a new(used) one..

 

2. Rebuilt motor/used motor.

 

3. Rebuild yours with new parts...this would be extensive, and the only way in my opinion would be the correct way, leaving nothing to chance. You'll want to check the crank, so dissasembly happens. A good crank man can check it for you. They are pretty tough, so I would guess even if affected, it could be reworked. Check crank bearings. New piston and rod for the damaged side, along with head work. Look at "good" head side. It will probably be ok for reassembly ...you have only 28k on this motor?

 

While dissasembled, weigh the "good piston" and rod assembly. You can match by taking weight from the bottom of piston area. A gram scale aids in the weighing process. Dremel tool does the job. Start slow , weighing each time. Do not remove too much from any one particular area. Do not remove any material from piston face or skirts.

 

All the other stuff is your choice...clutch,tranny, seals, etc...probably all ok. (but seals are cheap)

 

Maybe I didn't catch all the info:

 

Was this motorcycle insured? Why are you doing this yourself?

 

MB>

[Ken H.]

Was this motorcycle insured?

No.

Why are you doing this yourself?

Only way I'll be able to afford to fix the bike.

[StuGotz]

Ken:

 

glad to see your oil level is up

 

Remove the head studs and roll 'em on a good flat table.. this will tell if the block took the big "hit"..

 

Your head looks ok, except for the piston material hit. You can clean it up yourself. The valves look ok also. But removal and check might be in order.

 

Looks like you are on your way,

 

Good luck.

[kcscout]

Ouch. This is a painful one to read. I know how much you enjoy that bike and have put in to making it better than "like new".

 

Can't help you much on the technical/mechanical side, but if you need someone to share a beer/scotch/vodka/water with and help put the pieces back together, let me know.

[Twisties]

What has your insurance company to say. Might just be better to total the bike if you are covered,

I only carry liability on the bike. So it's fix it out of my pocket, or no bike.

 

Sounds like only one option to me... fix out of pocket.

 

So sorry to hear of the mishap. You might have seen that I dropped my RT on the way to Torrey this fall, just a mile from home. Never did figure out what I slipped on, but was just like the rear wheel had been greased. I imagine yours was a similar feeling, and I just remember thinking "this just isn't right" as I tried to pull it back under me.

 

Anyway, on the tech issue, although I admit to having no particular expertise, count me on the do the full rebuild or replace engine approach, e.g. +1 to mbelectric and others. I think you need that piece of mind, confidence, or whatever.

 

On the insurance front, don't know how much your bike is worth, but I can say full coverage on my RT is only $250/yr. My wreck, which was purely cosmetic except for a leaking cylinder head cover, and mostly one sided, came in, astonishingly, just over $7500.00.

 

I have a few things to say about that figure, which I won't say here, except that I think it could have been done well for half the amount. But either way, that covers something like 15 to 30 years of insurance. Bike ins is a great deal compared to car ins. You should think about it when you are back on the road.

 

We're pulling for you. Best wishes in getting running.

 

Jan

[Blast54]

Ken, If it were mine, the hell with new engines, splitting cases, sending crank out and all that.

I have put motors together using good ole Yankee Inginuity when neccessary and whatever was available for parts for 40 years. Everything from diesels,lawnmowers,motorcycles and even helped out on a couple of Corliss steam engines.

 

Call Recycle or Beemerboneyard, get a used jug/piston and slap it on. It will probably outlast you and the final drive I am not saying this is the RIGHT way to do things but if I doubted the condition of the crank/connecting rod and didn't have collision insurance, this is the route I would take....worse comes to worse...you are out a couple of hundred bucks....big deal.

[Ken H.]

Your head looks ok, except for the piston material hit. You can clean it up yourself.

Unfortunately the other side doesn't look so good. Can't think of a way to repair this:

 

 

And what of the fact that liquid poured into the intake runner gets by one closed intake valve. That's an issue, yes?

[ShovelStrokeEd]

The gouge in the sealing face could be repaired by JB Weld. The boss that is broken, depending on what it supports, could be replaced by a machine shop. Bore out the old, cut some threads in the bore, insert a threaded plug, stake in place with a small roll pin, face to height and drill and tap a new hole. There appears to be enough undamaged thread down there to pick up the center of the bore.

 

A couple of new intake valves and guides won't add all that much to the total $$$ for the repair.

[StuGotz]

 

<quote>

And what of the fact that liquid poured into the intake runner gets by one closed intake valve. That's an issue, yes?

 

I thought you were going to disassemble the head? You can look at guides, seats then..prob just a cleanup in order...

 

Speaking of cleanup, I'm assuming you have dropped the pan already..find any good alum stuff there? Check your pump, I hope you didn't distribute

debris to other areas.. You got to be careful about losing piston material, it has to end up somewhere..

[KDeline]

In my very limited knowledge, I would think the pistons would have to be spot on balanced. I think I would go the used engine route, if you could find one for a reasonable amount. Plug and play......???? Glad you are O.K.

[Ken H.]

The boss that is broken, depending on what it supports, could be replaced by a machine shop.

That is one of the four bosses that holds the valve cover on.

 

I guess I'm more concerned about the other side head surface between the head and the cylinder. There was a steel alignment pin between them, when the pin was pushed sideways it sheared off, but in the process it pushed up head material around it. Hard to photograph otherwise I'd post it. Admittedly there's a head gasket between them so I suppose a machine shop could mill the surface around the hole flat again. But the pin hole would still be elongated. It (and a new cylinder) could be drilled by a shop for a larger pin, but it would have to be pretty darn accurate for head to cylinder alignment. I guess the question is how far does one go on trying to repair this head vs. a new one?

[Ken H.]

I thought you were going to disassemble the head? You can look at guides, seats then..prob just a cleanup in order...

I'm going to, the guy who borrowed my valve spring compressor tool is suppose to bring it back to me today.

Speaking of cleanup, I'm assuming you have dropped the pan already..find any good alum stuff there? Check your pump, I hope you didn't distribute

debris to other areas.. You got to be careful about losing piston material, it has to end up somewhere..

Good thoughts, there is no pan to drop on a boxer motor however. The engine block/case is two halves bolted together down the middle. You have to disasseble the bike off the motor (literally as the rest of the bike is bolted onto the structural support motor) then split the case in half to gain access to the innards. Where I still may have to go...

[Ben_Ricci]

Sorry to read of your mishap. Glad you avoided injury. If anyone can tackle the bike repair, you can.

 

[smiller]

You got to be careful about losing piston material, it has to end up somewhere..

But not necessarily in the sump. Considering that material was only lost from the top of the piston and the engine stopped immediately thereafter it seems likely that the debris stayed within the bore/combustion chamber.

[ShovelStrokeEd]

Again, Ken, a machine shop should be able to repair that fairly easily. The locating dowel goes around the head bolt hole. It wouldn't be that difficult, given a new dowel, to determine the center of the hole, bore out the area and insert a plug, then bore the plug for the new dowel and clearance for the mounting stud. I have done this type of repair many times with nothing more than a vertical mill and a center finder.

 

If there is a raised area where the dowel was pushed over, it can easily just be filed flat with the sealing surface of the head. Again, a fairly simple operation that does call for some skill on the part of the operator to be sure he doesn't take too much off. Just mention draw filing to the machinist, he will understand.

[Ken H.]

You got to be careful about losing piston material, it has to end up somewhere..

But not necessarily in the sump. Considering that material was only lost from the top of the piston and the engine stopped immediately thereafter it seems likely that the debris stayed within the bore/combustion chamber.

That was my first thought too. But upon closer inspection of the piston, on the back side near one of the wrist pin supports there is a sliver of the piston missing. That piece most certainly went inward. One theory would be that it (and any other big pieces) will just work there way to the bottom and never make it through the oil pickup screen. Or downstream the oil filter to do any damage.

 

But I'm getting pretty long on 'wishes & a prayer' "theories" here.

 

I'm kind leaning toward putting a (used if I can find them) piston, cylinder, head and such on it, and fire it up and see what happens. If there is rod, bearing or crank damage it should be pretty obvious pretty fast, right? I would think it would knock and shake like a SoB. Then if I clearly have to tear it totally down then, the only thing I'd have lost is the time to put it back together the first time. But I'm still listening and thinking it all through...

[SHIMHEAD]

You got to be careful about losing piston material, it has to end up somewhere..

Don't forget that the missing material may well be in the exhaust system and can re-enter the cylinder on negative exhaust pressure pulses, destroying any repair work just done. It could also be in the intake tract. If you go the repair route, don't overlook these possibilities. Good luck and be thorough!

 

SHIMHEAD

[Ken H.]

The locating dowel goes around the head bolt hole.

Yes those are deformed too, but they're not the one I'm talking about. This pin is a solid pin not a hollow dowel, located at about 12 o'clock. So far I haven't been able to locate it on any parts drawings.

 

[BereIsland]

Glad your ok Ken

Steve

[George Brown]

Ken,

Sorry to hear about this, but glad you are OK! Bikes can be repaired or replaced.

[big-t]

If there is rod, bearing or crank damage it should be pretty obvious pretty fast, right? I would think it would knock and shake like a SoB.

 

Depends on how badly the parts are damaged.If they are only tweaked a little bit,it could be several hundred or several thousand miles before that little tweak or nick does enough damage to show up.

[Rotor]

Again, Ken, a machine shop should be able to repair that fairly easily. The locating dowel goes around the head bolt hole. It wouldn't be that difficult, given a new dowel, to determine the center of the hole, bore out the area and insert a plug, then bore the plug for the new dowel and clearance for the mounting stud. I have done this type of repair many times with nothing more than a vertical mill and a center finder.

 

If there is a raised area where the dowel was pushed over, it can easily just be filed flat with the sealing surface of the head. Again, a fairly simple operation that does call for some skill on the part of the operator to be sure he doesn't take too much off. Just mention draw filing to the machinist, he will understand.

 

Ken,

Having a working knowledge of car engines (and some bikes), I have to agree with Ed. If you decide to go with the repair option, I'm confident that head can be saved. Key is to find a "good" machine shop to do the work. As for the valve, it's probably bent just enough to leak.

 

Having never been past the valve covers of a Boxer myself, I wouldn't want to preform this job. But, if I were in your position and it was a do-it-myself or not ride situation; I'd dig in. I would, however, want the correct parts and it would drive me crazy until I knew both pistons matched.

 

Just my opinion on the matter...

 

Good luck, glad you're alright.