Go Back   ADVrider > Bikes > Old's Cool > Airheads
User Name
Register Inmates Photos Site Rules Search Today's Posts Mark Forums Read

Thread Tools Search this Thread Display Modes
Old 02-21-2004, 10:13 AM   #1
dp63130 OP
dp63130's Avatar
Joined: Sep 2003
Location: .
Oddometer: 305
1975 bmw r90/6 points

howdy.. I am trying to adjust the points (gap adjustment)on said bike but having a little trouble.
here is what the clymer says.
1. insert an allen wrench into the alternator rotor mounting bolt.
2. rotate the engine clockwise until the contact points are fully open.
loosen mounting screws securing contact blah blah blah..

So I pull off the cover exposing the points and alternator.. fire up the bike and watch the ignition advance unit spin but I dont see the points moving. At all. Nothing. No Movement what so ever.. but the bike is running. Now I have a bit of experince in mechanics but isnt this impossible? I can go take a quick MPEG of it if you want to see it.. dont points need to move? It is possible that they are grossly out of wack.. The bike has not been tuned for a year and half.

And since they arent moving how can I adjust them to be timed correctly -usually I would just rotate the engine until they open all the way then gap them to the correct limit(.35-.40mm)

Thanks for any help.
dp63130 is offline   Reply With Quote
Old 02-22-2004, 05:07 AM   #2
Boon Booni
Red Clay Halo
Boon Booni's Avatar
Joined: Aug 2003
Location: Richmond, Va
Oddometer: 13,764
maybe there's opening just a little bit.. ie: hardly any gap..

Or perhaps it due to the fact that they open and close twice per revolution of the cam, or at the same number of times as the rpms... even at idle 800-1000 times per minute (13 per second) may be hard to see..

Just crank it over slowly by hand and look.. If they still don't look like they're opening, adjust them till they do, gap them, and then set the points up statically with a test light..

Boon Booni is offline   Reply With Quote
Old 02-24-2004, 07:13 PM   #3
Gnarly Adventurer
pmdave's Avatar
Joined: Sep 2003
Location: Port Angeles WA
Oddometer: 105
The usual drill is:
a. disconnect ground wire at transmission (to prevent blowing up your diode board as you remove the front cover)
b. remove the front cover, then reconnect the ground wire.
c. remove spark plugs (to make it easy to turn over the engine)
d. remove rubber plug over timing window (LH side behind carb)
e. get a flashlight, lay down on the floor, and peer into the points cavity. You'll see the advance mechanism on top, and the points stuffed back in the hole. Some mechanics use a points cam tool temporarily installed in place of the advance mechanism. (like an advance mech with no weights on top)
f. If the points are burned or uneven, remove the advance mechanism, unscrew the points, remove, and either dress the points or replace them. If you can't remember ever changing the points, I suggest changing both points and condensor.
g. now, install the points, carefully crank over the engine (counterclockwise looking toward the front of the bike, or clockwise looking back at the front of the engine) to fully open the points. Set gap (as I recall, .014 in.)
h. connect a 12v light between the points wire and ground, turn on the ignition, and carefully turn over the engine until the light extinguishes. At the instant when the light comes on again, the static timing mark should appear in the center of the timing window (back behind the left carb) If it doesn't, unscrew the points screws slightly, and use a screwdriver to move the points until the light just comes on with the timing mark in the window. Yeh, this is difficult because you're squatting down trying to get behind the front wheel and around the advance weights (if you don't have the tool)

Now, when you think you have it timed statically, install the spark kplugs, turn on the gas, and fire it up with an inductive timing light sensing the left plug wire. Assuming it starts, check that the timing mark appears in the center of the window. If it doesn't, shut it down and go back to static timing with the 12v light. Just a smidgen makes a huge difference.

When you finally get the mark in the center of the timing hole with the timing light, rev up the engine and watch the timing marks in the window. You want the marks to advance up to the full advance position at say, 2800 rpm (or whatever the book calls for)

If it doesn't advance to the marks correctly (say it advances too little or too far) you need to remove the advance mechanism and check the little springs, lube the pivot points, etc. The springs are replaceable, so don't scrimp here. And don't forget to apply a dab of points grease to the advance cam. If there's a felt strip in there, lubricate it with a few drops of oil.

i. OK, once you've got it timed, shut it off, remove the battery ground wire, reinstall the front cover, and reconnect the ground wire. (and then do a carb adjustment)

Cautions include: don't try to crank over the engine with the alternator rotor bolt with the spark plugs installed. Don't try to remove the front cover without disconnecting the battery ground. Don't try to adjust the points with the engine running. Don't lay on a cold garage floor without your shorts on. Do paint the timing marks with some white paint to make them more visible in the strobe light.

pmdave is offline   Reply With Quote
Old 02-25-2004, 02:41 PM   #4
Frank Warner
Frank Warner's Avatar
Joined: Mar 2002
Location: Sydney, Australia
Oddometer: 6,593
Originally Posted by dp63130
So I pull off the cover exposing the points and alternator.. fire up the bike and watch the ignition advance unit spin but I dont see the points moving. At all. Nothing. No Movement what so ever.. but the bike is running.

the correct limit(.35-.40mm)
If the bike runs the points are opening...

Have you tried to measure the gap? 0.4 mm is a very small gap to see even when the gap is stoped, to 'see' it when the motor is runing .. well it may be better to watch for movment .. a very small movment.

I'd be measureing the gap, clean and adjust if required.. then re-time the spark.
Regards Frank Warner
motorcycles BMW R80 G/S 1981, BMW K11LT 1993, BMW K75 G/S
Frank Warner is offline   Reply With Quote


Thread Tools Search this Thread
Search this Thread:

Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump

Times are GMT -7.   It's 11:19 PM.

Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2015, Jelsoft Enterprises Ltd.
Copyright ADVrider 2011-2015