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Which piston do I have?


BamBam

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I am inquiring because my local BMW certified repair dealershop has no idea.

 

Last month my 2002 r1150rt was cruising down the highway when the engine RPM's dropped significantly. After a lengthy diagnosis it was determined that the right cylinder had lost most of its compression (<5 bars) while the other had a compression in the good range(approx. 165 lbs).

The right side was taken off and severe detonation had occurred between the rings. To the point where the rings could not be removed and the piston and cylinder were scratched up beyond repair.

I was told there were 2 different pistons for that model a 583-593 gram version and a 593-603 version. This weight included the rings and I believe the hardware to connect the piston to the rod.

My mechanic said they weight my piston and it was 657 grams.

Supposedly the serial number from the piston is not fully legible and they cant determine which one I have.

Now they want to take apart the good side to weigh the piston on the left side to help them figure it out.

 

Does anyone know what I can tell the to look for so they don't have to do this?

Thanks,

BamBam

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Evening BamBam

 

See if they can find the code AB+ or AB- on it --

 

(AB+ = 593-603GR AB- = 583-593GR

 

Otherwise remove the rings, pin & clips & re-weigh it.

 

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I am inquiring because my local BMW certified repair dealershop has no idea.

 

Last month my 2002 r1150rt was cruising down the highway when the engine RPM's dropped significantly. After a lengthy diagnosis it was determined that the right cylinder had lost most of its compression (<5 bars) while the other had a compression in the good range(approx. 165 lbs).

The right side was taken off and severe detonation had occurred between the rings. To the point where the rings could not be removed and the piston and cylinder were scratched up beyond repair.

I was told there were 2 different pistons for that model a 583-593 gram version and a 593-603 version. This weight included the rings and I believe the hardware to connect the piston to the rod.

My mechanic said they weight my piston and it was 657 grams.

Supposedly the serial number from the piston is not fully legible and they cant determine which one I have.

Now they want to take apart the good side to weigh the piston on the left side to help them figure it out.

 

Does anyone know what I can tell the to look for so they don't have to do this?

Thanks,

BamBam

 

What's the mileage? Also, how could the engine speed drop all of a sudden due to low engine compression?

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Dirtrider,

Thanks for the help I'll check with them on that. They mentioned trying to gently clean some identification on the piston. and evidently got to the point where they could see something but that it did not match what they had been told to look for.

Seems the rings cannot be removed. you can see on two sides of the piston where the head itself had pieces missing. They were in a V pattern to the first ring and sort of hourglass between the first and second ring.

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What's the mileage? Also, how could the engine speed drop all of a sudden due to low engine compression?

 

Kalali,

Mileage is 15 k(3 k by the first owner in 9 years, 9 k by the second in 3). Not sure how the first owner stored the bike. It may have been on the side stand leading to the issues in the right cylinder???

Compression may not be the only problem. when the RPM's dropped the engine light came on. It was not overheating and it acted as thought it was run out of gas. My guess is that the bike went into a "safe mode".

Checks from the BMW playbook were preformed and this was eventually the first glaring issue. Before it was taken apart it was found out that it would idle about 900 rpms with the choke on. With the choke off it would stall out in less than a minute. Adjusting the idle screw did nothing. There was an electronic device to help with the surging these bikes were prone to have but they also removed it as well stating "they would probably get it to run smoothly and that they had not seen those devices in years. Time will tell.

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Morning BamBam

 

When they get it back up & running have them check the ignition timing as some riders diddled with that on the early 1150's to try to remove surging.

 

With all that sitting & few miles per owner I think I would also send the fuel injectors out for cleaning & flow testing. A partially restricted injector can cause a lean cylinder & piston/ring/valve damage.

 

I would also run a fuel pressure/flow test as internal fuel tank hose leaks (very common on older 1100/1150 bikes) can easily cause a lean-run condition.

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Morning BamBam

 

When they get it back up & running have them check the ignition timing as some riders diddled with that on the early 1150's to try to remove surging.

 

With all that sitting & few miles per owner I think I would also send the fuel injectors out for cleaning & flow testing. A partially restricted injector can cause a lean cylinder & piston/ring/valve damage.

 

I would also run a fuel pressure/flow test as internal fuel tank hose leaks (very common on older 1100/1150 bikes) can easily cause a lean-run condition.

 

Thanks for the extra help. Earlier this year I had them do a replace all fluids job (I think basically a 12k mile check). At that time I know they replaced some plastic fuel connectors from the tank with metal ones. I would hope they checked that out then(???)but I'll ask anyway. They called me last week to get my permission to take apart the left side to weigh that piston. I'm not exactly confident in them at this point. After it did take 3 weeks to tell me the compression was low in the right.

 

I know the second owner did all the work through the dealership but I know nothing of the first owner. I'm guessing since they removed the fuel surge fixer that when they get it back together they will have to check the ignition timing?

 

Also, wouldn't the computer adjust the fuel flow to avoid the damage?

 

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Also, wouldn't the computer adjust the fuel flow to avoid the damage?

 

Afternoon BamBam

 

The fueling computer can only adjust the fueling when running in closed loop & then only within reason. It can't make up for one side running real lean under heavy load.

 

As for removing the other side piston-- that probably wouldn't be a bad idea anyhow as it is probably carboned up & should be cleaned to match the new piston side anyhow.

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Often the techlusion "fuel nanny" type devices make the mixture very rich. This can lead to heavy carbon buildup on the piston and eventually a piece of carbon will break off and cause expensive damage.

Normally, I've seen the carbon wedge a valve open causing interference but I guess it's possible the damage can cause this problem too.

I would really think about pulling the other head to check carbon build up or use a good bore scope to see what's going on inside the other cylinder .

 

 

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Noted about checking the other piston. This fix will be expensive for the right alone. I'm not exactly what device was used but the piston was quite black. They mentioned trying to gently clean the piston to see the serial number and still really couldn't make it out. That is why they wanted to take apart the left side. Compared to Snakepliskins's post the piston is quite dark. There is no shine to the top of it. is there some sort of additive that would clean up the piston chamber. maybe a fuel additive?

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There are many additives, some do something, (Marvel Mystery Oil) but most are snake oil.

If heavy carbon is an issue, I would be concerned about a product loosening a chunk of carbon.

Like others, I suggest just bucking up and having the other head pulled to de-carbon and to help ID the piston. Get it over with.

 

And in my jaded "dealer mentality" opinion, put it back to stock with the correct CAT plug and spark plugs, don't baby the thing, rev it, and if the surge is THAT bad, up shift to get away from it.

I may suggest having a dealer set the synch and valves the first time as an individual who does this several times a day, every day, for perhaps a few years has a much better "feel" than a person who maintains 1 or 2 motorcycles a few times a year.

 

 

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