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Topic-icon Timing RPM

  • Humble Bub
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1 week 4 days ago #6871 by Humble Bub
Timing RPM was created by Humble Bub
A quick question on timing. 1991 R100RT. I have read numerous recommendations as to the optimum RPM for timing which seem to range from 3,000 to as much as 4,500. Mine shows the Z marker centered at 2,800. Further advance of throttle moves the Z up and almost out of view. My question - how critical is RPM and what is best practice?

Thanks as always
Craig

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1 week 4 days ago #6873 by 8166
Replied by 8166 on topic Timing RPM
It's pretty simple, really. The timing should be set at FULL advance.

In your case, the timing is set with too much advance, as evidenced the Z mark disappearing from the window as you increase the RPMs. Loosen the bean can, move it a little bit in one direction, snug up one of the screws, and run the RPMs up until the timing mark won't move in the window any more. That's full advance, and if you're lucky the line next to the Z will be centered in the window. If not, move the bean can, and check again.

8166 Scot Marburger, This email address is being protected from spambots. You need JavaScript enabled to view it.

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1 week 4 days ago - 1 week 3 days ago #6877 by arni
Replied by arni on topic Timing RPM
to expand a bit on Scots comment: the timing is set at full advance and you have no choice about what RPM full advance happens unless you open up the bean can and modify some things. The RPM for full advance is built into the mechanism. So you can forget RPM and just rotate the beancan until the Z mark and the crankcase mark line up.

You do have to wind the engine up enough so you are in the range of full advance. Won't work at idle. Try 3500-4000 rpm. You should be fully advanced by then.

I loosen one screw on the beancan and tighten the other so i can rotate the can and it will stay where I set it. Then I drape a blaze blanket over the nearside header so I don't fry my arm on the header (again), wind up the throttle and lock it with the throttle lock screw then rotate the can to put Z on the mark. Shut down, tighten beancan screws, disconnect battery ground and sew it up.

www.lowes.com/pd/Oatey-Soldering-Flame-P...AvD_BwE&gclsrc=aw.ds
Last edit: 1 week 3 days ago by arni. Reason: spelling

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1 week 3 days ago #6879 by Humble Bub
Replied by Humble Bub on topic Timing RPM
Thank you both.
Craig

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1 week 3 days ago - 1 week 3 days ago #6880 by Wobbly
Replied by Wobbly on topic Timing RPM
► Full Advance is a function of the particular ignition type and brand you have on your bike. Don't forget, we're writing for the larger audience here, which represents 5 or 9 different ignition systems, both stock BMW and aftermarket.

► Your strobe will show you where your engine reaches Full Advance. As you watch the timing window and slowly rev the engine progressively higher, various timing marks will come into, or go out of view. When that progression of marks stops, that is, when the next 100 higher RPM fail to make the marks visually advance... then you have found Full Advance. That is the definition of Full Advance: The engine speed at which the ignition ceases to advance the ignition timing. The strobe lamp simply does the visual "stop motion" effect, which allows you to see this happening.

► The strobe will also show you how sloppy your ignition unit is. If your view of the timing mark is dancing all around in the window, forcing you to do some kind of mental averaging, then you probably have a mechanical points system... and now you see how bad it can get with 40 years of wear on the mechanical advance unit. Or, if the timing zooms from Full Retard at idle right up to Full Advance at a very low point (say for instance) 2200 RPM, then you can see that your advance springs are shot (stretched out due to age). This because it's the springs that resist the mechanical movement toward Full Advance. All this as opposed to the latest EI unit, which will present a rock solid visual of the flywheel timing marks. And this is because the "advance" is a pure mathematical calculation done within the EI software.

Hope this helps

Don't hide 'em, Ride 'em !!
#15150
Last edit: 1 week 3 days ago by Wobbly.

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1 week 3 days ago - 1 week 3 days ago #6883 by arni
Replied by arni on topic Timing RPM
I'm an old man, disabled and my hands shake badly. It is difficult for me to type so I leave the long dissertations on every conceivable situation to snowbum and the like and just answer the OP's problem or question about their bike. I send a short dissertation to Bob occasionally about errors in his dissertations, and they are very few. I am writing for the person who asked. if you wish to publicly include me in a "we're" please consult me back channel first. This gives me the opportunity to bow out if I disagree. Oak alienated a lot of people and I noticed years ago that there was an 800 lb. gorilla in this room too. have you noticed? (hint: where is everybdy?)

Off the top of my head I can think of three ways to determine maximum advance. Two are slow and one is fast. You covered one of the slow ways, I thought I would throw out something about one of the fast ways. Something I have leaned from the pro mechanics is how to be a whole lot faster. Speed = making flat rate or better = making a living. I'm sick of wrenching. I've been doing it a long time and it has gotten old. Fast = more riding time.

If one is truly going to write for the broader audience then one has to mention that some bikes are not timed at full advance at all, they are static timed. When a magnetic, inductive, optical or Hall trigger is used in place of points the bike is timed at full advance. Points are static timed. It is possible to static time the others but one must build a gizmo to display the state of the trigger.

Years to not wear advance mechanisms. Miles and poor maintenance do. When one is worn it wears symmetricly The classic double image on a points bike is a cocked cam nose. I do not know about the newfangled units with all the plastic parts. I could see one of those just blowing up. I protect mine with exotic lubricants. I have never seen stretched springs caused by anything other than hamfisted wrenching. The advance should not be disassembled unless one knows exactly what one is doing and has a good touch. !00k+ miles and the springs were like new. But I haven't seen everything.
Last edit: 1 week 3 days ago by arni. Reason: punctuation, removed streams of profanity.

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