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Old 11-07-2010, 06:55 PM   #31
bikecat OP
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Quote:
Originally Posted by supershaft
I guess that busted ring didn't gouge the bore?

The broken ring was still in place, so I guess it did not affect the surface of the piston.


Quote:
Originally Posted by supershaft
... I wouldn't be surprised if those exhaust guides are looser than a goose.

Exhaust guides? Is this something I can check during valve clearance or I have to address it now? Thanks loads.

Cheers
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Old 11-07-2010, 07:06 PM   #32
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I meant the surface of the cylinder bore.

Rings do effect the piston's ring grooves! I would call that the surface of the piston. Ring grooves have specs just like the rest of the stuff in question.

Knowing the specs is one thing and taking accurate measurements is another. It takes skill, tools, and experience. And then it takes some experience knowing what top end specs BMW pulled from outer space and what specs work here on planet Earth.
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Old 11-07-2010, 07:11 PM   #33
bmwrench
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Those look like Black Diamond valves to me. The black coating often wears on the stem, particularly at the bottom and to a lesser degree at the top-which is where all valve stems wear. It doesn't seem to hurt anything as the stem itself is supposed be nitrided. The thing to watch for on these valves is transfer of guide material to the stem. If this is the case, both valve and guide should be replaced. If no metal has transferred and you measure clearance, be aware that this assembly needs at least .003" clearance to survive.

The right piston crown indicates that it has had water in it-probably from the crankcase vent. I'd bet that the top ring started to rust to the bore at some point and that the ring broke when the motor was started.
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Old 11-07-2010, 07:16 PM   #34
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Quote:
Originally Posted by bmwrench
Those look like Black Diamond valves to me. The black coating often wears on the stem, particularly at the bottom and to a lesser degree at the top-which is where all valve stems wear. It doesn't seem to hurt anything as the stem itself is supposed be nitrided. The thing to watch for on these valves is transfer of guide material to the stem. If this is the case, both valve and guide should be replaced. If no metal has transferred and you measure clearance, be aware that this assembly needs at least .003" clearance to survive.

The right piston crown indicates that it has had water in it-probably from the crankcase vent. I'd bet that the top ring started to rust to the bore at some point and that the ring broke when the motor was started.


Some history might help. The bike stood in tropical weather for nearly 3 years between 2003 to 2005 and then another 3 years in the workshop while the rebuild was taking place.

This is a steep learning curve for me (I have no mechanical background), and I am grateful for the advice given.

Cheers
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Old 11-08-2010, 10:00 AM   #35
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Quote:
Originally Posted by bmwrench
Those look like Black Diamond valves to me. The black coating often wears on the stem, particularly at the bottom and to a lesser degree at the top-which is where all valve stems wear. It doesn't seem to hurt anything as the stem itself is supposed be nitrided. The thing to watch for on these valves is transfer of guide material to the stem. If this is the case, both valve and guide should be replaced. If no metal has transferred and you measure clearance, be aware that this assembly needs at least .003" clearance to survive.

The right piston crown indicates that it has had water in it-probably from the crankcase vent. I'd bet that the top ring started to rust to the bore at some point and that the ring broke when the motor was started.
Have you seen Black Diamond valves with the stems so perfectly polished before? I haven't. I don't think I have ever seen any that didn't flare the keeper grooves quite a bit as well. Were the keepers ground short so the valves didn't rotate? That's the trick to getting crappy wearing keeper grooves to last longer.

I have set up MANY a BMW airhead guide with WAY less than .003 stem/guide clearance. They worked perfectly AND let a LOT less oil by for a lot longer time. Hellfar, I have set up MANY a BMW airhead piston/cylinder with less clearance than that! Don't get me wrong, I am not big on real tight guides on most engines but airheads don't have seals and it makes a big diff! The ONLY way to run tight guides, or even looser guides IMO, is to size them yourself with a Sunnen valve guide hone. IMO, all other methods are comparatively a like using a chisel. Most people don't have access to a cylinder dial bore gauge let alone a guide dial bore gauge. IMO, measuring both with anything else (of course it takes micrometers to use the bore gauges) is a joke.

I bet you're right on about that right piston. That isn't wear. It's corrosion.
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Old 11-08-2010, 10:16 AM   #36
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My post about valve stem to guide clearance applies to Kibblewhite's "Black Diamond" parts, not OEM or other aftermarket parts, and only the exhaust side at that.

Yes, tight guide clearances, where they will work, are a Good Thing; better oil control and valve sealing, leading to longer-lasting valve jobs, less noise,etc.
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Old 11-08-2010, 11:11 AM   #37
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Bloody interesting stuff guys keep it going. If the valve guides are rooted how are they replaced?
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Old 11-08-2010, 11:34 AM   #38
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Quote:
Originally Posted by bikecat

There's also something that looks like a "$" sign?




That "dollar sign"
is just the makers mark. It is a K on top of an S which mean Kolben Schmidt
pardon my German spelling.
Kolben means piston
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Old 11-08-2010, 01:05 PM   #39
supershaft
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Quote:
Originally Posted by bmwrench
My post about valve stem to guide clearance applies to Kibblewhite's "Black Diamond" parts, not OEM or other aftermarket parts, and only the exhaust side at that.

Yes, tight guide clearances, where they will work, are a Good Thing; better oil control and valve sealing, leading to longer-lasting valve jobs, less noise,etc.
Smokey Yunick said that he found tight guides causing power loss through oil suction. I think I know what he is talking about but is is hard to explain. He does a good job of it. Tight guides might also reduce valve seal because they don't allow the valve room to find the seat's center. I have never noticed any leakage caused by that while leaking down hot engines with tight guides but . . . . At any rate, the upside of tight guides outweigh the downside in our engines IMO.

I don't understand why you would run Black Diamond valves if you have to set up the exhaust guides well on their way to being worn out for them to work from brand new?
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Old 11-14-2010, 04:03 AM   #40
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While waiting for my piston rings, I took time to clean the cylinders. Interesting, they seemed similar except for the print "GILAROONI 1" AND "GILAROONI 2" at the base of the cylinders:



There might be also similarities in the "5S C" on the "1" cylinder and "?? C" on the "2" cylinder.





What are these? Does it differentiate between left and right?

Inside the cylinders there are lines and I'm told that they look normal.



Cheers
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Old 09-30-2012, 04:25 PM   #41
sigpe57
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Quote:
Originally Posted by fishkens View Post
Do NOT use silicone on the push rod seals. a) They work fine w/out the goop,
Few questions about a push rod seal replacement.

-No Silicone on the push rod seal replacement job at all?

-Can I put back the head without using the H-alignment piece?

-Some owner leave the piston ring and the head and remove the connecting rod instead. What's the reason? I found remove the piston from the housing is easier.

Thank you for the reply,

TT
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Old 10-03-2012, 06:47 PM   #42
bmwrench
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The reason for keeping the head on the cylinder is to save the price of a head gasket. Hardly worth it in my opinion. It is a good idea to leave the piston in the cylinder so as not to disturb the rings, but if you had you would have not seen that broken ring. Since the late wristpins use external snap rings, I remove the cylinder complete with the piston and remove the piston on the workbench. When reassembling I find it much easier to get the piston and rings into the cylinder on the bench.

It's not surprising that the bike ran well with a broken ring; you just had a second gap in that one!
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Old 10-04-2012, 12:17 PM   #43
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Quote:
Originally Posted by bmwrench View Post
If you have to replace a lifter, soak it overnight (at least) in motor oil. They are cast iron and absorb oil, just as an iron frying pan does. Whether you are replacing them or not, smear the faces with cam assembly lube, or if you don't have this ass'y lube, get some CV Joint grease from the local auto parts store. The first minutes of use for lifers and cam are the most critical in their lives.
In a former life when starting an engine with a new cam and/or lifters it was highly recommended to raise the RPM well above idle ASAP as it supposedly would decrease the load on the lifter face and get it spinning to avoid the initial "first minutes" wear for both the lifter and cam lobe.

Preset everything, valve adjustments, ignition timing, fluids etc etc and double check everything. Engine starts and runs, gets oil pressure, no fluids spraying out or other immediate problems then rev it up a bit and hold it. I think we used to try for 2000 rpm for 20 minutes. However a running airhead will not stay cool so a few minutes may have to be good enough.
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Old 10-04-2012, 01:12 PM   #44
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Quote:
Originally Posted by bmwrench View Post
The reason for keeping the head on the cylinder is to save the price of a head gasket. Hardly worth it in my opinion. It is a good idea to leave the piston in the cylinder so as not to disturb the rings, but if you had you would have not seen that broken ring. Since the late wristpins use external snap rings, I remove the cylinder complete with the piston and remove the piston on the workbench. When reassembling I find it much easier to get the piston and rings into the cylinder on the bench.

It's not surprising that the bike ran well with a broken ring; you just had a second gap in that one!
That's how I do it too. Seems like a better controlled situation for re-inserting rings in the jug.
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Old 10-05-2012, 04:12 AM   #45
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When putting it together use Dreibond or Yamabond on the cylinder crankcase join.

When you have the top end together, check oil flow to rockers by turning the engine over on the starter (plugs removed and grounded, rocker covers removed) and you will easily see that oil is getting to the rockers.
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