Hello, all.  Started with assumption that I'd reshim valves, but I didn't expect that would solve my oil burning issue.  Took head off, cleaned valves and depressions up a bit.  Tested valves via the water/compressed air method.  No bubbles at all.  The cylinders look pretty scratched up and the throttle bodies butterfly valves look really crusty to my untrained eye.  I wager that this is a hone+rings job.  What else am I missing.  Why would the throttle body valves be so crusty?  Pics follow.

cant see the bores that well ...just a lighting issue I guess
but do I see some score marks around the bore ?  down a bit ..? or is it just oil marks ?

don't forget these bores are a nicasil coating ...not steel   so ask questions before going in there to try to refinish them

the throttle bodies do clag up a bit as a natural occurrence ..( the valve overlap spits back a fair bit of carbon crap )

get in there with some throttle body cleaner  for the tbs '
and or perhaps you have a fair bit of leakage of the rubbers from the throttle bodies to the plenum (box that sits on top ) and the crankcase to plenum z type  tube ...often found to be cracked and leaky

perhaps you can add a light for the bores pic ? after you wipe out the cylinder with a degreaser soaked cloth ??

Nicasil bores don't give up easily. I know from experience that they will still show the factory hone marks after 150,000miles+. The carbon on the butterflies should be pretty soft: I cleaned mine with an application of brake cleaner. It near fell off as the cleaner hit it.

As Charlie says, the crankcase-to-plenum chamber link pipe will need changing. If you're pulling the throttlebodies off then change the rubberware top and bottom of the throttlebodies. The intakes (top) will be split and the inlet spigots will probably be split. Not worth not doing if you're that far in.

Looked in the bores again and, indeed, all the marks are on diagonal and crisscross, so that's all original.  Is there a way to tell whether the rings are shot without removing all the pistons and with the engine apart?

No. You need to measure the ring gap but truthfully, I'd be surprised if they were shot. If you do need to replace them, the good news is that the break-in period for new rings in old nicasil bores (according to Moto Guzzi) is as low as 200 miles. I have no idea what the engine loading should be over that period as I used to break my Guzzis in by feel and by ear.

FreyZI wrote:Looked in the bores again and, indeed, all the marks are on diagonal and crisscross, so that's all original.  Is there a way to tell whether the rings are shot without removing all the pistons and with the engine apart?

Are you burning a lot of oil(more than a quart in 800 miles)?  If so, you have your answer.

When I bought the bike, it was inoperable.  It's never been ridden during my ownership, so no way of knowing this for sure.  I think it burned a significant amount of oil the first time I started it up, but I suppose that could have been due in part to not having been on in two or three years.  I've only had it running for a few minutes at a time, a couple of times.

just burning off residue I suspect

take it for a good 200 mile run

after fixing any vacume type leaks as mentioned before
lots of threads in here about replacing rubber bits

you can see the oil level in the sight glass ?

Bricks do not like sitting, a mates bike that had sat for quite a few years was a prodigious smoker. It eventually started to settle with more mileage, and now only smokes if left on the side stand or after sex. If it worries you can try using a high detergent oil for a couple of hundred miles and then change over.
Regards Martin.

The funny thing is, I probably can't take it out for a 200 mile spin, as I have no tags and it has to pass inspection to be registered.  Maybe I can conjure Ferris Bueller and run it (though sadly not in reverse) with the wheel in the air for a couple hours.

Engine rubber, e.g., connections to throttle bodies and plenum, really doesn't look that bad once it's cleaned up a bit.  I did replace the crankcase breather hose.

Yes, I can get a good read on the oil level.

So, maybe put Alda back together and try again?  Or, since I have it apart, except for the bottom, er right, end, just check it all out while she's open.  Other than head gasket, they all look reusable, or can't I get away with that?

I wish I had the problem that she only smokes after sex!

if you have it apart

perhaps a delicate valve grind- lapping would be advantageous ...I do recall you saying no leaks through the valves
also remember that almost all rubbers are or are becoming cactus ...I know I would be popping the valve springs out and installing new valve stem seals

good luck

Good advice, Charlie.  I may as well replace valve stem oil seals while top end is off.  Meanwhile, I took out pistons and at first glance everything looks okay.  Pistons are all within spec.  Seems like there is a very small amount of wear (at least enough to rub off any deposits) on the skirts on opposite sides which would be top and bottom as they sit in the engine, i.e., 90 degrees from the gudgeon pin axes, which I presume to be the normal wear pattern.  I haven't checked all the rings yet, but all of piston 3's rings are well within spec.  Glad to see that rings are probably good -- I priced them (assuming I would at least replace the oil scrapers) and they are ridiculously spendy, especially since they seem to sell them only as a set of three for cylinder.

One little trick I found in inserting the piston rings to check end gap, a beer can (fortunately I had one handy) works perfectly for pushing the ring into the cylinder a bit, past any taper.

BTW, can anybody confirm that the valve seals are the same as those (same part number) for BMW 3-series automobiles?

My 4V RS uses a fair bit of oil so I am rather interested in this thread.  I replaced the valve guide seals with a small effect on consumption.  What is confusing is that the compression on my engine is still good, despite the oil usage.

Did you find a lot of carbon buildup in the ring grooves in the pistons?  When I had my head off I found a fair bit of carbon buildup on the valves and piston faces.  I am suspecting/hoping that carbon buildup may be causing sticky oil control rings.  Am trying to convince myself to do a tear down this winter, but following the problems I had with a cylinder head bolt when I did the valve guide seals, I am a bit reluctant.

Point-Seven-five wrote:
Did you find a lot of carbon buildup in the ring grooves in the pistons?  When I had my head off I found a fair bit of carbon buildup on the valves and piston faces.  I am suspecting/hoping that carbon buildup may be causing sticky oil control rings.  Am trying to convince myself to do a tear down this winter, but following the problems I had with a cylinder head bolt when I did the valve guide seals, I am a bit reluctant.

.75, I did find a fair bit of gunk inside the ring grooves, but I wouldn't characterize it as carbon build-up.  I scraped it off with a micro screw driver and found it to be more of a rusty color, for whatever that's worth.

I also had a lot of build-up on the faces of the valves and pistons.  The Haynes manual suggests metal polish for these parts to make the surface less attractive to would-be deposits.

Point-Seven-five wrote:My 4V RS uses a fair bit of oil so I am rather interested in this thread.  I replaced the valve guide seals with a small effect on consumption.  What is confusing is that the compression on my engine is still good, despite the oil usage.

Whatever happened to regular use of Marvel Mystery Oil? That's second only to emu oil in benefits to humankind. It's red, too!

High detergent oil can sometimes free up sticky rings. Run it for one to two hundred miles or what ever the specific oil's instructions state. Then switch back to your regular oil.
Regards Martin.

Alas, I've tried the high detergent several times, even added a can of engine cleaner to the crankcase before oil changes, all with no joy.  Either the oil control rings are shot or they are coked in place beyond cleaning without disassembly.

I wonder if it is more of a 4v problem than a 2v problem. A mates 4v used to smoke a lot then the smoke eventually settled but it still used oil and I've heard of a couple of others over the years. It might be worthwhile seeing if different pistons and or rings were used between the two. At least on the Brick you can do it with the engine in situ but it is still a pain, possibly a winter job coming up.
Regards Martin.

One big problem with using a high detergent oil is that it can and often does clean the carbon deposits from behind the compression rings causing them to collapse with the usual results.