Fouled Right Plug

[Manfred]

I think I've seen this addressed before but was unable to find it. If it's on the forum, please direct to the thread.

On my recent trip to Arkansas, my bike fouled the right plug while going up and down big hills - lots of closed throttle coasting downhill. The bike also consumed about a quart of oil over the 2,000 miles.

I recall reading about an oil breather or something that fouls the right plug and causes oil consumption.

Anyone know more?

Thanks :-)

[20774]

I'm not sure on the '87 bikes, but on my /7, the oil breather directs any oil mist to the RH carb. I suppose under a lot of trailing throttle, oil splashing forward/backwrd, etc., an extra amount of oil mist could be generated and head out the breather.

Here are a couple of threads I found regarding fouled plugs:

http://www.bmwmoa.org/forum/showpost.php?p=233408&postcount=1

http://www.bmwmoa.org/forum/showpost.php?p=121898&postcount=1

Is this a problem at any other time or just on up/down hills and coasting throttle?

Wait a minute, there are "big hills" in Arkansas? :stick Define big!!

[Manfred]

I'm not sure on the '87 bikes, but on my /7, the oil breather directs any oil mist to the RH carb. I suppose under a lot of trailing throttle, oil splashing forward/backwrd, etc., an extra amount of oil mist could be generated and head out the breather.

Here are a couple of threads I found regarding fouled plugs:

http://www.bmwmoa.org/forum/showpost.php?p=233408&postcount=1

http://www.bmwmoa.org/forum/showpost.php?p=121898&postcount=1

Is this a problem at any other time or just on up/down hills and coasting throttle?

Wait a minute, there are "big hills" in Arkansas? :stick Define big!!

Thanks! I'll check into those threads.

This happened on BIG hills in southern Missouri - Hwy 86 - about 500 feet up then DOWN. Happened a second time heading south on AR-27 towards I-30. Not as big but lots of closed throttle coasting. Hasn't happened before. I am running a cooler plug than normal, as recomended by Snowbum for the hot clime I live in. It was plenty cool in the hills - 65 or so.

After the plug fouled - each time - it kinda cleared up and the bike would run fine and pull OK up to 5,000 RPM; no power above that (made passing cars exciting!).

[lostboy]

If this problem occurred while, or after, all this hill work, the oil consumption is due to the extreme vacuum generated while coasting down hill with the throttle closed. It is time to pull the heads and cylinders and check for wear.

[Manfred]

If this problem occurred while, or after, all this hill work, the oil consumption is due to the extreme vacuum generated while coasting down hill with the throttle closed. It is time to pull the heads and cylinders and check for wear.

That's exactly how it happened - but only the right plug fouled. I haven't checked compression since I bought her, will do that tomorrow.

[lostboy]

How many miles does the bike have on it?

[Manfred]

As it sits tonight, the odometer reads 55,555.

[Manfred]

Compression test today, hot, WOT:

Right = 150 psi
Left = 148 psi

Nearly spot on with the specs for optimum compression.

[lostboy]

Unfortunately, an oily cylinder can give you better compression figures than the motor really has. Likewise leakdown testing. You can get a reasonable idea about oil control problems with a good small flashlight. Shine it into the cylinder via the spaark plug hole while slowly turning the motor over. In a healthy boxer, a small amount of oil will be seen on the wall and at the bottom of the piston's crown. A large amount means trouble.

[mymindsok]

If youre fouling the right plug, it's because the breather is blowing excess oil into the right carb and from there into the engine.

Try these maintenance tips:

1) Make sure that you breather valve is working correctly and replace the disk if you have the old style valve.

2) Do a leak down test to see if the rings need a replacement. At 60,000 you are probably ready for a top end refresh, no matter what kind of compression youre running.

3) Are you using 20/50? If not, do so.

4) Fill the crank case to 1/2 way between the full and add marks on the dipstick. Any more and the engine case is too full.

This much info works for 99% of Airhead riders.

[ccolwell]

How low does your oil level go? My '84 R100 used a lot of oil -- at least until I realized that any oil added over 1/4 the distance from the minimum to the maximum level on the dipstick would just be blown into the RH carb. It would drop to that level and no further.

500 ft. isn't very high; these things were made to work in the Alps.

[Manfred]

If youre fouling the right plug, it's because the breather is blowing excess oil into the right carb and from there into the engine.

Try these maintenance tips:

1) Make sure that you breather valve is working correctly and replace the disk if you have the old style valve.

2) Do a leak down test to see if the rings need a replacement. At 60,000 you are probably ready for a top end refresh, no matter what kind of compression youre running.

3) Are you using 20/50? If not, do so.

4) Fill the crank case to 1/2 way between the full and add marks on the dipstick. Any more and the engine case is too full.

This much info works for 99% of Airhead riders.

I've researched the breather and, while I haven't looked at mine yet, the old style that caused this problem was stopped being used long before my '87 was built - but I will look at mine soon and see for myself.

I plan on performing a leakdown test soon, knowing the compression test is only a single data point. I would not think a properly maintained BMW would need a top end "refresh" at 60,000 miles - none of my Yamahas did.

I do use 20W50

I have been filling the case to about 2/3rds between the marks, to see how low it "wants" to be. After the run in the hills, the oil level was at the low mark. I'll monitor it closely in the next couple weeks to see how it does.

I did notice white smoke coming from the exhaust a couple times upon first thing start-up in the morning, parked on the side stand. But that would be the left cylinder.

[Manfred]

I bought a leak down tester, but have to rely on a friend for the compressor. He's out of commission for a while, due to his off-road event on our trip to Arkansas last month.

However - this morning I checked the valve clearances. Both valves on the right side were too tight. No sign of lots of oil pooling up in the cylinder. I adjusted the valves and will keep on eye on it and hope to run the leak down test in a week or so.

[PMonk]

Hi from the guy that forgot to meet you for lunch at Tuffy's.
Am now in Angel Fire NM. Hauled up my old /6 and waiting for the rain to go away.

I have much the same problem with my /6 and ordered the newer breather kit. Yours is a simple reed valve so I don't know if they ever go bad. My blow by is so bad I have oil dripping on the garage floor from my right carb even after driving on our flatland.

Still would like to get together for a ride when we get home from the mountains.

[Manfred]

Paul,

Good to hear from you. Sorry about your oil breather. From what I've read about the newer ones, which is what my bike has, they don't contribute to the oil consumption problem.

Hope you can correct your problem.

I will be going on camping trip with my wife (cage with pop-up) next month.

We can get together when we get back.

[Manfred]

Since I adjusted the valves on the right jug, no oil consumption. I went on a spirited 120 mile ride today and upon safely arriving home, the level is the same it's been for over a week - about 3/16ths above the "ADD" line. From what I've read, that's good.

[beemerPhil]

The breather on your '87 dumps into both intakes, left and right. Ever since the "EPA" airbox w/ the flat air filter, 1981 or so. The previous poster with the /6 has a single breather line that dumps into the RH carb only.

Valve adjustment could contribute- so could altitude, though I doubt this is your problem if you never left Missouri. Big hills- hah!

You didn't mention the bike's mileage- how old are the ignition wires? Guides are pretty predictable- are you sucking oil? A quick look at the plugs will tell you if you have an oil control problem; airheads run pretty clean unless something's wrong. Coasting down a long hill under no throttle is the highest vacuum the intake will ever produce; if anything is passing oil into the chambers, this is where you'll see it first.

Also, have a look at your cold-start levers on the carbs. Make sure they return all the way to the seated position- dirt gets into the cold-start valves through the hole in the air passage created when the gasket shrinks from engine heat, and the spring isn't beefy enough to pull them shut all the way through the crud. You shouldn't be using the cold-start valve gaskets in a hot climate; if you find that they're leaking (spray some carb cleaner at the valve cover while idling, you'll know) clean 'em up and use a good sealant SPARINGLY applied to the cover's egde. These carbs weren't designed for much heat, the gaskets will fail quickly in hot weather or traffic; they shrink, and pull into the air passage at the back side of the valve. The air leak that results is no big deal at first, it's a tiny gap- but it's unfiltered air, and the dirt & dust will soon gum up the valve. I haven't used a gasket here for 25 years.....silicone, etc works better.

Or you could just put in the right plugs and see if it solves itself......:stick

[Manfred]

The breather on your '87 dumps into both intakes, left and right. Ever since the "EPA" airbox w/ the flat air filter, 1981 or so. The previous poster with the /6 has a single breather line that dumps into the RH carb only.

Valve adjustment could contribute- so could altitude, though I doubt this is your problem if you never left Missouri. Big hills- hah!

You didn't mention the bike's mileage- how old are the ignition wires? Guides are pretty predictable- are you sucking oil? A quick look at the plugs will tell you if you have an oil control problem; airheads run pretty clean unless something's wrong. Coasting down a long hill under no throttle is the highest vacuum the intake will ever produce; if anything is passing oil into the chambers, this is where you'll see it first.

Also, have a look at your cold-start levers on the carbs. Make sure they return all the way to the seated position- dirt gets into the cold-start valves through the hole in the air passage created when the gasket shrinks from engine heat, and the spring isn't beefy enough to pull them shut all the way through the crud. You shouldn't be using the cold-start valve gaskets in a hot climate; if you find that they're leaking (spray some carb cleaner at the valve cover while idling, you'll know) clean 'em up and use a good sealant SPARINGLY applied to the cover's egde. These carbs weren't designed for much heat, the gaskets will fail quickly in hot weather or traffic; they shrink, and pull into the air passage at the back side of the valve.

Or you could just put in the right plugs and see if it solves itself......:stick

Thanks for the note, Phil.

I closed off the EPA pipes IAW Snowbum's method (inserted a 5/16th inch ball bearing in each pipe, near the airbox).

I use half-choke on a cold start. I'll check to see if the cables are seating well at the carbs and check the gaskets you mentioned - this would seem to be a more likely culprit. I know about using carb cleaner (or WD40) to check for vacuum leaks - my Yamaha Virago taught me that :-)

I put new spark plug wires on the bike in Feb, more than 5,000 miles ago. Bought them from MotoradElektrik.

I'm using a one-step colder plug per Oak's guidance, based on where I live. Seems to run better than with the stock plugs that were in it when I brought it home.

[beemerPhil]

I closed off the EPA pipes IAW Snowbum's method (inserted a 5/16th inch ball bearing in each pipe, near the airbox).

Those are the "pulse-air" system tubes; not part of the crankcase breather system, their purpose is to inject a dash of fresh air into the hot exhaust gas to promote further combustion of leftover fuel- sort of an economy catalytic converter. They had no effect on performance, but the popping exhaust noise, esp. on deceleration, bugged a lot of folks- myself included. Sounded awfully ratty for a BMW, but it was easily fixed by blocking the tubes as you said.

The early EPA airbox was a problem, though you'd have to ride pretty hard to notice its effect. The idea behind the "horns" on the airbox cover was to produce a pulsation in airbox pressure that would drive the diaphragm air pumps that feed the exhaust air tubes, but the design was shipped prematurely. Airflow was severely restricted at high engine speeds/open throttle; the bikes would choke, and in many cases would actually go faster if you backed the throttle off. (You'd probably never notice this til 90+ mph, so only a few enthusiastic riders objected.)

Service bulletins from BMW described 2 or 3 different stages of drilling strategically located holes in the air horns and/or cover, none of which achieved anything that I could detect. Cutting the horns off completely worked just fine......problem solved, bike ran like an R100 at last!
The later covers(made of plastic) didn't seem to have as much trouble- and the horns could be snapped right off anyway. Put some screens over the holes, or mice will move right in!

As always, YMMV :dance

[Manfred]

I may have discovered one thing that was contributing this problem on my bike: the float on the right side carburetor was too high. I've adjusted it per the Bing manual and hope to see some improvement.

BeemerPhil, I am intrigued by the notion of cutting the horns off the air box and will look at doing so next time the gas tank is off.

[PMonk]

Got the updated (reed valve) breather on, but not running yet. I did the spline lube and couldn't believe how easy that went. My input shaft was replaced 15k miles ago but the splines were bone dry. I think that is going to be at least a yearly chore. Pulled the battery carrier out to bead blast and paint and decided to go ahead and replace the clutch and throttle cables.

I was amazed how much air is moved through the breather. Had plugs out and turned the engine over with the kickstarter and placing my finger over the outlet of the breather cover I could feel some suction on downstroke and lots of air displaced on the upstroke.

Hope you found the problem with the fouling. If it was gas fouled you should have a black powdery looking plug? If oil fouled kind of oily looking?
I have been running NGK BP7ES plugs, but on the ride to Waller the other day I had run BP6ES which is one range hotter. When I pulled the 6ES they looked too white (hot) so I am going back to the 7's. Think you are on the right track running a cooler plug especially during the summer.

[Manfred]

Got the updated (reed valve) breather on, but not running yet. I did the spline lube and couldn't believe how easy that went. My input shaft was replaced 15k miles ago but the splines were bone dry. I think that is going to be at least a yearly chore. Pulled the battery carrier out to bead blast and paint and decided to go ahead and replace the clutch and throttle cables.

I was amazed how much air is moved through the breather. Had plugs out and turned the engine over with the kickstarter and placing my finger over the outlet of the breather cover I could feel some suction on downstroke and lots of air displaced on the upstroke.

Hope you found the problem with the fouling. If it was gas fouled you should have a black powdery looking plug? If oil fouled kind of oily looking?
I have been running NGK BP7ES plugs, but on the ride to Waller the other day I had run BP6ES which is one range hotter. When I pulled the 6ES they looked too white (hot) so I am going back to the 7's. Think you are on the right track running a cooler plug especially during the summer.

Paul,

Glad to hear you're making progress on your old boxer. Some say lube the splines every two years, some say pulling the rear wheel back ain't good enough. I don't have enough experience to know for sure :-)

The fouled plug I had, as best I recall, was hard, black deposits on the plug. After some more time, I'll check the plug to see how it looks.

FYI, I will likely be riding past your part of the state once again as I plan to head back to central La for an airhead tech-day on 9 & 10 Oct. You should join me - it will be a fun weekend.

[pmdave]

Typically, excess oil consumption and oil fouling plugs (black, greasy, soot) are a result of oil being sucked through the intake guides with the throttle closed. IOW, when you are descending a steep hill with the throttle closed, the engine is trying to suck in more air, and whenever an intake valve is open it can suck it past the guide--which happens to have an oil source handy.

The fix in the automobile world has been to install seals on the tops of the valve guides. And I see that one BMW head rebuilder will do this, too.

pmdave

[Manfred]

This has nothing to do with the oil consumption, but I did discover my right side carb float valve was set too high. I set it to spec and get 30 miles more per tank! :thumb