Smoking R100gs?
 

Hello. Someone help me out here. Last week i gave my '89R100GS/PD a complete fluid change, motor, filter and transmition. I used Golden Spectro 4 synth. blend 20w50 in the motor(78000miles, runs strong!)Also, as per the Haynes manual i re-torqued the heads and adjusted the valve lash to spec.Motor was cold to the touch. I did notice one exhaust valve had no lash to begin with?!? This valve now makes a lot of noise. The bike now runs 100% better, idles correctly and smoother excelleration, but when i start it in the morning, it smokes like a chimney! Grey-blue with an oily smell. It also seems to fire on 1 cylinder for the first couple of revs until the second cyl. catches up. This smoking only lasts until the bike is warm, which leads me to believe oil is leaking into 1 cyl. overnight. Is this possible on a flat twin airhead? The bike is on the centrestand overnight, so oil can't spill into the cyl.(i'm only assuming this might happen??) Like i said, the bike runs much better, but at the cost of burning oil? This really conserns me, and it never did this when i bought it. Any air-head advice out there?

Ron,

I think you got the one valve at the wrong point on the stroke. If it was tight before and super loose and noisy now...

Another problem on these can be the rocker arm end play - needs to be right. Search the HUBB only on "rocker arm end play" - first hit tells you all you need to know.

As for the smoking, if it's overfilled the oil will leak past the rings. Generally a problem on the left side when on the sidestand, but it could be when on the centerstand. Also, when shutting the engine off, just let it idle for a few seconds, then turn the key off. A little blip and then turning it off sucks oil into the cylinders and will smoke madly next day.

It could also be simply the engine is loose, possibly needs rings, and the synthetic is just too thin when cold. A full compression test could give you a clue there. Test dry, then with a few squirts of oil in the cylinder. Big difference = worn rings. Be sure to test full throttle.

Also could try plain old 20w50 GTX or whatever. If that's the only real change, then ...

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Grant Johnson

Seek, and ye shall find.
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One world, Two wheels.
www.HorizonsUnlimited.com

Hello. Thanx for all the great advice, today was a day of discovery. Before tearing into the bike, i took some time to study the maintinence history. The previous owner took meticulous notes, oilchange every couple thousand miles religeously. It appears that one valve, and never the same one was tight every time the valve-lash was set. This no longer concerns me, as it matches the history and the bike still runs strong. Today, i preformed a compression test. Here are the results:
L.side:120 dry, 122 wet.
R.side:135 dry, 142 wet
This tells me i have a problem with the left side. What concerns me the most is the scratches i see in the cylinder walls on both jugs. They appear to be crosshatch marks from a cylinder hone, but the very deep ones are left over. Could be the compression problem? There is no record of cylinder, rings or head work.I also found evidence of sand in the bottom of the airbox. Hard for me to believe sand could cause such a constant scratch patern. Also the crankcase vent tubes are filled with oil and emulsion. For now i gave this all a good clean while a ponder my next move. The bike has 78000miles under what appears to be a good owner. Any sugestions?
Thanx!

The crosshatching is normal - "they all do that sir". http://www.horizonsunlimited.com/ubb/wink.gif

It's still there from the original factory crosshatching - shows how little the nikasil cylinders actually wear. Mine was also still showing marks at 120,000km.

Valve grind is almost certainly indicated, possibly rings - NO honing, just new rings. But first I'd do a valve job, and leave the cylinders alone. Also new valve guides almost for sure, possibly exhaust valves.

Sand in the airbox = check the little rubber one way valve at the bottom center rear of the airbox - almost certainly perished - replace.

"crankcase vent tubes are filled with oil and emulsion" = water in the oil, probably from condensation. Also possibly overfilled. Change, and done.

------------------
Grant Johnson

Seek, and ye shall find.
------------------------

One world, Two wheels.
www.HorizonsUnlimited.com

Hello. Returned from a final road-trip of 1000 miles or so before i tore down the motor. Left exhaust valve is cracked, split and sunk into the head. This caused mis-alignment with the guide, wearing it out rapidly and causing oil to flow into the chamber. time for a re-build, i'm considering dual-plugging while i'm at it. Ant thoughts on this?

I've heard that it's a good idea?

I believe that you may need to adjust (advance?) the ignition timing to gain best results. This in turn may necessitate the use of a higher octane fuel, which is okay if it's available.

Steve

Bummer on the valve guide etc. Not a big deal to fix though, and then you'll know you're 100%. Assuming you also do the other side...

As for dual plugging, btdt, yes it's good.

Ignition timing gets retarded, not advanced - the dual plug effectively advances it by providing a dual flame front, thus burning the charge sooner than normal with a single plug. This means you can use a lower octane gas without ping. http://www.horizonsunlimited.com/ubb/smile.gif OR raise compression for more power, but that's not our gig here. http://www.horizonsunlimited.com/ubb/wink.gif.

All you need is to get the plug holes drilled by someone who knows what they're doing - VERY important - and the right coils. Mine were installed in 1987, and they're still fine, no idea what is currently available, but shouldn't be hard to find. (They're big yellow guys, I think Accel) Oak Okleshen sold me my mine. (Contact through Airheads).

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Grant Johnson

Seek, and ye shall find.
------------------------

One world, Two wheels.
www.HorizonsUnlimited.com

hi ron
go for the twin pluging makes a world of difference the way they should have been build.also your be able to start it by kick start.hey grant finely started an r100 by kick start o so easy when its twin plugged

nobby

Thanx guys! Nice to hear from you nobby! Cleaned the heads and inspected them yesterday. All but one valve is fine, only need to replace the left exhaust. Valve seats look good, need new guides though. Going to look into the dual plugging today and get a quote on the re-build. Any thoughts on polishing the ports?

Good onya nobby!

Next step is non-twin plugged. http://www.horizonsunlimited.com/ubb/smile.gif

Had a good time with Brighty before he left on his rtw tour. He came by with his R100GS - non-dual-plugged and said ne couldn't kick start it. After much demonstrations etc, he still couldn't. Not sure he ever did manage it. He got really ticked when I started his. http://www.horizonsunlimited.com/ubb/smile.gif Of course I learned how to kick a bike on a Ducati with fixed advance ignition... ANYTHING is easy after that.

Point is, it CAN be done - but yes it's a bitch. Dual plugging does make it easier.

Ron, re polishing the ports - you're not so much after polishing as smoothing the ports. The stock BMW ports aren't well matched up with the intake spigots, and aren't especially smooth. You could certainly get some improvement if an expert puts a little time in on it.

DO NOT POLISH. You need a little turbulence to break the flow up and prevent dead spots on the walls of the ports. Polishing can actually reduce the effective size of a port.

------------------
Grant Johnson

Seek, and ye shall find.
------------------------

One world, Two wheels.
www.HorizonsUnlimited.com

Hello.
Over the past few months i've done considerable work to the bike. Heads were completely re-built , dual plugged and ported. I also had one stripped exhaust thread removed and replaced. Excellent job at a good price provided through a machinist Shail's deals with (Powell st. Vancouver)
I've been using the internet and specificly this site (Thanx Grant http://www.horizonsunlimited.com/ubb/smile.gif and tonight i think i discovered why i might of burned out my valves. When i changed my oil i replaced a gasket for the cover with three bolts. The bike was purchased this way. Tonight i discovered the gasket causes low oil preasure and sometimes even by-pass! Could it be the motor didn't receive enough oil for 3000 miles or more. The lifters were badly scored and needed replacement along with the entire valve-train. I left the bottom end alone, but can't help wonder what kind of damage may have been done? Any thoughts?

Normally "burned" valves has nothing to do with the oil.

The gasket on the oil cover is all part of the infamous "$2000 o-ring" problem.

Ther is a very good article on it by Snowbum, http://home.jps.net/%7Esnowbum/Oil.htm

If indeed you did have the gasket etc wrong, 3000 miles without a disaster is doing well, and if that is the way it WAS, then it's probably ok.

Work through the article and check it out carefully - ESPECIALLY noting YEARS of the problems. I do NOT belive yours is involved in the real problems - just have to make sure that yours is correctly assembled per factory specs.

Note that the bottom end on the airheads is almost indestructible - possible, but unlikely, UNLESS it ran out of oil pressure. You DID grab the rods and try to move them around when you had the cylinders off of course? http://www.horizonsunlimited.com/ubb/smile.gif

You can also pull the rods easily and have a look at the journals when the cylinders are off. Just be sure to replace the rod bolts and nuts.

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Grant Johnson

Seek, and ye shall find.
------------------------

One world, Two wheels.
www.HorizonsUnlimited.com