Adjust valves - confused.

[azcycle]

I've gotten myself thoroughly confused trying to adjust the valves this evening.  Help!

Right cylinder, bike in 5th, and I have a straw in the spark plug hole to help me gauge when the cylinder is at the top.  I rotate the wheel and the intake opens and closes... rotate and the exhaust valve opens and closes....

Now when I come BACK to the intake there seems to be a lot of pressure. Is THAT TDC? The straw seems to be at the top, but the intake rocker arm has a ton of play in it...I can wiggle it up and down.

Are both intake and exhaust rocker arms supposed to be snug before I adjust... no looseness or play?

When I continue to turn, there is a sudden movement, the intake opens and closes really quickly, and then  I'm back to the exhaust.

Just not sure exactly where TDC is.  

[nhmaf]

TAke the rubber timing plug cover off the left side engine case by the clutch housing bell.   The flywheel is visible through the hole.   a SMALL bit of metal on the outer edge of the flywheel will have some stamped marks in it.   We usually put a bit of white paint on them and wipe it off before it dries - to leave the white paint in the recesses of the letters to make them more visible.  There will be (3) letters/marks somewhat close to each other as far as distance along the circumference goes.   There is an "OT" mark that indicates  TDC.    A short distance from this is an "S" mark which is the timing mark that should be centered in the hole when the bike is idling at ~1000 RPM - this is about 6 degress before TDC.  There is a "Z" mark which is about 26 degrees further which is the full advance point (@3500 RPM).    When the OT is visible in the timing window, the engine is at top dead center, but one cylinder is on the compression stroke and the other is on the exhaust stroke.   The side that is on the compression stroke will have both valves closed at this point, and there should be a gap between the ends of the pushrods and the rocker arms.   There will be no tension/pressure on the pushrods and you should be able to move the rockers (at least enough to take up any gap to the pushrods).   It is under this condition that you set the gap for the valves.    If the valves on one side aren't both closed with some play in the rockers when the OT comes up in the window, then that cylinder is likely on the exhaust stroke and the opposite cylinder is on the compression stroke -> turn the engine some more until the one you're interested in comes up on compression stroke (or just take both valve covers off and go to whichever side is on the compression stroke, adjust as necessary, turn engine some more until TDC and other side is on compression and adjust it).  After I adjust both sides I manually turn the engine through a couple more times to recheck my work - you also

[Mike V]

Graeme,
It may be easier to remove the spark plugs. Near your dipstick you'll find a black rubber plug. Remove it, this is your window to the flywheel markings that will show you where TDC is by a stamped tab with "OT" on it.  Bump the wheel until you see the intake valve close, continue bumping the wheel until you just see the exhaust valve start to open. Bump the wheel in the opposite direction and peek through the hole you uncovered. You want the OT punch or line (which ever you might have) centered straight through the window. This should be TDC. Adjust valves for that cylinder and repeat the procedure for the other cylinder. Here's a picture of what you want to see.

[darrylri]

Rather than do it this way, with the straw, pop the little rubber bung off the bell housing on the left side and shine a light in there.

As you rotate the rear wheel, there are two tabs that will go by the hole in rapid succession.  The first has a hash mark with a Z -- this is full advance.  The second has a hash and an S below a hash and OT.  The S is full retard.  OT is top dead center.

When you position the motor so that the hash mark above OT points to the witness mark on the left side of the hole, one side of the motor will be at the top of the compression stroke and the other will be at the top of the exhaust stroke.  The valves on the compression stroke must be closed, so if they're set right, their rockers will both wiggle some.  The valves on the exhaust stroke should both be at least partially open, and the rockers will be tight.

Your description sounds like you're rotating the rear wheel too quickly.  There is time for two strokes between the intake closing and the exhaust opening.  However, after the exhaust opens, the intake will open before the exhaust closes (this is what's called overlap -- as the last of the exhaust is being pushed out of the cylinder, it begins to pull fresh charge in from the intake).

I just set the valves on my bike yesterday, using the method above.  In 5th gear, you only need to turn the rear wheel about a quarter turn to go through all four strokes.

[nhmaf]

The straw in the sparkplug hole will help you tell when you are getting close, but if things have somehow gotten very much out of wack and the gap between both pushrods and rockers has closed up to nil, you need to go by the "OT" mark centered in the timing hole to make sure that you're on the button.   Again, the TDC on compression side should have looseness in both intake and exhaust pushrod/rockers.

I only put the bike in 2nd or 3rd gear so I can more easily "creep" up on TDC - in 5th gear it is too easy to shoot right past it.  And DO take both sparkplugs out to make things easier to turn.

NICE PIC, Mike V!

[azcycle]

Thanks for the photos... they helped. Spark plugs had been removed. Cracked open the timing cover plug, rotated the engine until I saw OT, and measured what I had done on the right cylinder.  Turns out I did it right.

My problem was that I loosened the intake rocker adjusting nut so much so it had a ton of slack in it, and I couldn't figure out why. But I just tightened the adjusting nut and it snugged up perfectly. Measured intake .002 and exhaust .008, double-checked and I think I'm good.

Will do the left side tomorrow.

And have to buy some valve cover gaskets, as the right one tore when I removed the cover.  

[darrylri]

The intake should be .004".

And have to buy some valve cover gaskets, as the right one tore when I removed the cover.  

Par for the course.  The center stud came out with one of the nuts on mine, and I had a hard time getting the nut off the stud.  If the gasket isn't too bad, you can turn it with the torn part up and use it temporarily.  Using a bit of goop in the tear could help as well, but you shouldn't need any on the sealing surfaces.

[nhmaf]

+1 The intakes should be at .004 inches.

Once you get new gaskets they should last you for years.   Note carefully how they go on (there is a "top" and "bottom").   you will want to put them on so that they tend to stick on the head in proper position - not come off with the valve cover.

[montmil]

Right! 0.004-Intake and 0.008-Exhaust will have your scoot making nice BMW music.

Monte

[azcycle]

Ah, .004 intake... got it.


Okay, so plugs!  These plugs are OLD.  That being said, the right plug looked perfect... nice and tan, perfect. However, left plug was in okay shape: Tan with some carbon deposit and the insulator has just a TINY bit of blistering on it, as does the electrode down near the base.

So, what do you all think? Go with the same plug (NGK BP7ES) and take a look after a bit of running with the new valve clearances?

[Semper Gumby]

Sheesh and I've been using .006" on the intake since 1993.  Must be the older bike...

[Mike V]

I'm using .006" intake and .008" exhaust on my "new" 81 R65 top end. I'm thinking I may want to open the exhaust to .010" until after break-in. Then what? The owners manual states .002 intake and .008 exhaust. Man, .002" intake seems tight to me. I'm kind of glad this subject came up. What are you guys using as a safe operating range with a broken-in motor?

I have the new lead free conversion valve seats and Swiss-made valves.

-Mike V. / 650 newby

[Barry]

.002" intake seems tight to me.

BMW originally specified intakes at  .002" and in a later service bulletin increased it to .004".  I think you can also find .006" in print some place.

Service bulletin attached

[Mike V]

Barry, I think one of the guru's instructed .004" Iintake and .008" Exhaust for the 650, that seems like a good formula to me for a broken-in motor. I currently have the valves set at .006" and .008" but I may want to open the exhaust a bit for a few hundred miles.
Sorry AZ, don't mean to step on your topic here. Just curious what you guys are comfortable with and what works best...Barry, Bob, Rob, Monte, Semper, et.al.?

[Semper Gumby]

I might try it at .004" and see if there is any difference in sound/performance.

The tighter the valve lash the more advance the valve opening.  What effect this has on engine tune is beyond my pay grade -- but there will be an effect.

Other thing is what is good for the Goose (1981 light flighwheel R65) might not be good for the Gander (pre-1981 heavy flywheel R65)

(paging a German engine dynamics engineer who speaks english)