Whoa Smoke, me too!

[awshucks]

'81 R100T 41k, starteds smoking a bunch left side on cold start. Eliminated side stand issue and I think reed valve, disconnected air box to intake set up and let oil collect in air box for 140 miles or so. Didn't solve smoke problem. Had put about 1000 miles on new to me bike w/o problem.

Pulled heads and cylinders today, lot's of burnt oil build up on left, minor signs of same on right.

Minor delay to get spring/valve compressor tomorrow, pics then. Did find both pistons had ring gaps aligned. Left w/ in 1" for all 3, right side, nearly a straight line for all 3. Compression test shortly before all this showed about 115, same both sides.

Mechanic buddy says it's normal for rings to spin on pistons whilst running, what are the odds they both ended up the same or nearly so? Does his airplane engine knowledge apply to Beemers?

Also, had rumors of one of two PO doing some valve work due to '81-84 having exhaust seat/valve condition. Can't get any paper work, but did check valves w/ magnet, both exhaust valves non magnetic, both intake are magnetic.

Does anyone know what's up w/ that? Were they that way from BMW or does this tell a tale?

We're going to check the end gaps on rings tomorrow, will know more then. Tia for advice or comments!

 

[20774]

The main issue with the '81-84 bikes was the seats. They were of a metallurgy type that didn't conduct heat well. I've not heard of way to determine what kind of seats are in the head. If there's doubt, then there's doubt...change 'em.

 

[pmdave]

Valve guides are often the culprit in letting oil into the combustion chamber, especially if the valves are not closing properly.

This is typically an intake guide issue. On the intake stroke there is a vacuum in the combustion chamber. Oil from the outside of the valve area gets sucked in through the guide, especially when the bike is slowing down under compression.

Many cars and some bikes use seals on the tops of the guides, but I've never seen them on BMW bikes. If there is excessive clearance, the fix is to replace the guides and valves.

Of course, oil can be pumped past the rings as well. I'd measure the rings to ensure they don't have excessive end gap. Insert the rings into the bore, and check the gaps with a feeler gage. Use the piston upside down to push the rings square with the bore, and check both high and low in the cylinder to check for taper.

Bear in mind that carbon on the upper end increases the compression ratio. So, If I were doing one side, I'd pull the other side, decarbon, and touch up the valves (at least.)

pmdave

 

[pmdave]

Non-magnetic indicates stainless steel. I'm under the impression that stock BMW exhaust valves are stainless steel valve heads friction welded to carbon steel stems. I'm sure if I'm wrong about this someone will correct me.

However, some airhead owners have been taken in by the hype from aftermarket suppliers who sell valves made entirely of stainless steel. And there have been a number of catastrophic failures of these aftermarket valves. I'd suggest checking the exhaust valve stems with your handy magnet. If the stems are stainless, I'd replace the valves with the latest BMW stockers, including the latest valve seats. I believe the "latest" valves and seats have a 33 degree angle rather than the earilier 45 degrees.

So, beware aftermarket parts advertized as "longer lasting", "more power" or "cheaper than BMW". If you need a little convincing, I could probably find those photos of the piston that tried to eat a loose valve top, and another that bent the valve after the (tapered) aftermarket exhaust valve stem hung up in the guide. I can assure you that it cost me quite a bit more than a full valve job with BMW parts.

pmdave

 

[James.A]

I'm with Dave on this one. I personally experienced a valve failure with an all stainless, after market exhaust valve on a 750. Less than 1000 miles on the head work. High RPM but never close to red line. Valve bent, top of piston hit. No way to know for sure exactly how or why. Only BMW valves for me from now on.

 

[awshucks]

thanks! gotta check those valves out in an hour or so when mech get's here.

What's up w/ my new oil filter being a folded two piecer? Seems like there's an extra gasket w/ embedded big white 'o' ring.

Dealer says it's all they make now, I don't do 'new' well, lol.

 

[pmdave]

Out of curiosity, I checked some valves with a magnet. I don't have any record of which is which.

All of the intake valves (including two new BMW) are magnetic heads and magnetic stems. That would indicate steel alloy, and possibly the valve heads being the same material.

All of the exhaust valves (used) had non-magnetic heads. Most had magnetic stems. Some have non-magnetic stems.

I'm thinking that BMW valves are probably stainless steel alloy heads welded to hard steel stems. It could be that the valves with non-magnetic stems are some of the aftermarket SS valves that didn't fail but got changed to avoid future disasters.

pmdave

 

[pmdave]

For some time there have been two oil filter designs, on straight for non-oil cooler models, and one hinged to make it easier to remove and install.

Max BMW shows the straight filter as part no. 11421337570.

It's possible that BMW could have deleted the straight filter, but I'm suspicious that your dealer has a lot of hinged filters in stock and wants to move them. I usually buy filters in small quantities, but I'm about out. I hope I'm not in for any surprises.

Bear in mind that the filter cover must provide the correct pressure on the white O-ring, and that's controlled with shims. I suggest doing a search for the correct techniques and acceptable depths. Both Glaves and Parkhouse have discussed this many times.

pmdave

 

[beemerguru]

Most dealers only stock the hinged filter now..one for engine with coolers and one for engines with no oil coolers.

Rule of thumb, watch what comes out and the order of things. Take the old white O ring that came out and roll in between your fingers..it should be slightly flattened on both sides.

That tells you whatever came out is what should go in. All the oil filter kits contain extra parts that may not be needed for your model bike.

You'll know when you finish an oil change and start the bike...red light better go out immediately and stay off at idle...if not..STOP and go back and look again at what came out and what went in...or this becomes what's known as the $2K "O" ring..

Matt's article is very good at educating you on why and how everything goes together and each compoment's relation to the whole..read it first.

 

[mneblett]

If the stems are stainless, I'd replace the valves with the latest BMW stockers, including the latest valve seats. I believe the "latest" valves and seats have a 33 degree angle rather than the earilier 45 degrees.

This is the only thing I would *not* do. When I took my heads to Tom Cutter for dual plugging, he removed the valve springs while I was there so we could see what condition the valve guides were in. They were (my words) terrible -- very loose, permitting a lot of side-to side play at the valve head (certainly explained the oil residue build-up in the combustion chamber) -- this on a motor with only 16K on it. Tom immediately put it down to BMW's having switched from 45 degree valves to 30 degree valves in 1988. My heads had the guides replaced, seats recut to 45 degrees, and new 45 degree valves fitted to the new guides.

 

[jforgo]

Why the change?

This is the only thing I would *not* do. When I took my heads to Tom Cutter for dual plugging, he removed the valve springs while I was there so we could see what condition the valve guides were in. They were (my words) terrible -- very loose, permitting a lot of side-to side play at the valve head (certainly explained the oil residue build-up in the combustion chamber) -- this on a motor with only 16K on it. Tom immediately put it down to BMW's having switched from 45 degree valves to 30 degree valves in 1988. My heads had the guides replaced, seats recut to 45 degrees, and new 45 degree valves fitted to the new guides.

Yes, I have also heard the 45's give better service life. I have not heard the other side; why BMW changed this.

 

[20774]

You'll know when you finish an oil change and start the bike...red light better go out immediately and stay off at idle

Greg -

I'm not sure if it's universal on all the bikes, but on my /7, the oil pressure light is amber. The charge lamp is red.

 

[awshucks]

The intake valves are magnetic at both ends, exhaust magnetic at opposite end from seat, appears to be stock valves. The exhaust valve is shot, sharp edge on outer diameter and seating area stepped. Seats in heads 'looked good' but intake guide clearance seemed too big compared to exhaust valve guide clearance. Couldn't mic the bore of guides, knew they were getting shipped tomorrow any how.

Can't make heads or tales of my Clymers on rings. What's w/ the color codes? [figured that one out] We couldn't mic the pistons or cylinders either, will have to go to shop in town and have another mechanic buddy do that. Didn't understand the letter grade[A,B,C] pistons, is that marked somewhere on them?

I'm guessing if I know the piston, cylinder, diams and ring gaps, proper replacement ring size won't be a problem? Not quite clear on concept whether or not diff ring sizes are available?

Didn't measure accurately the rings end gaps, but will. Couldn't get rings square to bore of cylinder, noticed slight bit off there appears to make big diff's in gap. Kept thinking about Clymers instruction to 'use piston', that finally sunk in a few minutes ago, lol.

One bright side, the finned exhaust nuts came off great thanks no doubt to liberal apps of Kroil.

 

[carlo]

My 1982 R100RT will smoke out the left side after parking on the sidestand every once in awhile, sometimes more often, sometimes less often. The Brown sidestand on mine allows it to lean way over when parked. So much so that I put a piece of 2x4 under it when I park it in the garage at night.
I've always attributed the random nature of the smoking to be due to piston rings ending up with their gaps aligned towards the bottom of the cylinder bore occasionally. If your bike does it all the time, perhaps your rings are stuck? They are supposed to rotate as the engine is running.

(edited) I presume that yours quits smoking after a few seconds? Mine does on the times when it smokes on start-up.

'81 R100T 41k, starteds smoking a bunch left side on cold start. Eliminated side stand issue and I think reed valve, disconnected air box to intake set up and let oil collect in air box for 140 miles or so. Didn't solve smoke problem. Had put about 1000 miles on new to me bike w/o problem.

Pulled heads and cylinders today, lot's of burnt oil build up on left, minor signs of same on right.

Minor delay to get spring/valve compressor tomorrow, pics then. Did find both pistons had ring gaps aligned. Left w/ in 1" for all 3, right side, nearly a straight line for all 3. Compression test shortly before all this showed about 115, same both sides.

Mechanic buddy says it's normal for rings to spin on pistons whilst running, what are the odds they both ended up the same or nearly so? Does his airplane engine knowledge apply to Beemers?

Also, had rumors of one of two PO doing some valve work due to '81-84 having exhaust seat/valve condition. Can't get any paper work, but did check valves w/ magnet, both exhaust valves non magnetic, both intake are magnetic.

Does anyone know what's up w/ that? Were they that way from BMW or does this tell a tale?

We're going to check the end gaps on rings tomorrow, will know more then. Tia for advice or comments!

 

[carlo]

thanks! gotta check those valves out in an hour or so when mech get's here.

What's up w/ my new oil filter being a folded two piecer? Seems like there's an extra gasket w/ embedded big white 'o' ring.

Dealer says it's all they make now, I don't do 'new' well, lol.

I don't think they sell anything but the hinged filters anymore. Those are supposed to allow you to replace them without removing the exhaust system. I found that to be a bad idea, and will go to the trouble of removing my RT fairing lower and exhaust headers whenever I replace the filter.
I don't recall exactly where the white o-ring fits, but I've always been able to see where it goes when I've replaced my filter. All the parts that come in the kit seem to match what I've always found inside my filter housing.