Timing an R100RS (Dual Plug).

[Rotifer]

Greetings from Yorkshire, England.

My '78 RS has not been sounding too happy for a while, and though I am fairly sure the carbs are somewhat out of balance, I've a feeling the ignition may be slightly retarded -- so I'd like to check that first.

The PO had electronic ignition fitted, and the dual plug conversion carried out, and I understand the latter affects the timing, making it retarded at the standard setting.

If anyone can advise on the correct procedure, particularly the appropriate view through the timing window, I'd be grateful.

Rotifer.

[Barry]

Dual plugging doesn't affect the ignition timing in itself rather the improved combustion provided by dual plugging allows you to retard the timing which improves efficiency and economy. Retarding the timing on dual plugged engines is the excepted norm. You can just retard the timing by anything from 6 - 9 deg or leave the static timing alone and limit the maximum advance by 6 - 9 deg or some combination of the two. There lots of debate and info on the net about timing dual plugged airheads. Tom Cutters document actually shows how retarded static timing should look in the timing window.

http://rubberchickenracinggarage.com/Downloads/TomCutterDualPlugIgnition.pdf


Also check out Snowbums page on dual plugging

http://bmwmotorcycletech.info/dualplugging.htm

[tvrla]

I tried everything and didn't have too much luck. The R100RS I got was dual plugged and also has the 1050 kit. The jetting had been modified and it got rotten gas mileage, ran so so, and made me wonder why go to all the trouble and expense for this?

I read Cutter's info and tried that, and Snowbum and Curve, but it was Oak that set me on the right track.

Contact Oak and get his write-up on the subject. He was probably the first to research dual plugging and has the best info. He mailed me his paper from the early 80s documenting the research and development that went into dual plugging. It'll help you understand what's going on there so you'll be able to think with the data.

My main jets were drilled out 170s, and the timing was very retarded. Now it's got 150s, static timing is at the normal setting (or slightly retarded), full advance is another 500 or 1,000 rpm higher but retarded a couple degrees. It now gets between 45 and 52 mpg and goes like stink! A real blast to ride.

I highly recommend getting in touch with Oak. He da man!

[Rob Valdez 79 R65]

I highly recommend getting in touch with Oak.

AskOak at aol.com

[Lucky_Lou]

I highly recommend getting in touch with Oak.

AskOak at aol.com

I will second that i emailed a question and got a very quick solution.
Lou

[Rotifer]

Oak came through with a speedy response, so thanks for the tip folks.


"1) At idle speed, the timing should be adjusted so that the OT mark ( Top dead center) rests in the timing window about half way between the middle and the top of the timing window. If any jitter in the mark, raise the mark slightly. ( Ignore the S mark )

2) When the engine speed is throttled to full advance ( 3500 or so RPM) the F white dot should be just ever so slightly below the lower edge of the timing window".

I've borrowed a fancy timing light, so I'll set my plug gaps, and valve clearances, warm her up, and see where we are.
I'm fairly sure that Oak's advice differs from that which I originally followed, so I'm very interested to see how the old Frau goes when she's sparking like she should.

I'll let you know the result, as soon as the wet winter weather relents. Many thanks for the help -- much appreciated.

Rotifer.

Too young and thin to ride a Harley.

[Barry]

What Oak describes is equivalent to retarding the ignition by about 3 Deg at idle and by 4 or 5 Deg at full advance.

Did Oak mention anything about the notch in the timing window ?

The factory put a notch in the left hand side of the timing window as reference for setting the timing. In an ideal world this is in the centre of the window as shown in Tom Cutters illustrations but it can be off centre quite a bit my own is approx. 2 deg below the centre of the window. You may want to allow for this if yours is also off centre.

[Rotifer]

Hi Barry, thanks for pointing that out - Oak referred to the window as a whole (no pun intended), and certainly I've seen an illustration of a notch well above centre, so maybe there's a connection.
The notch is central on my RS.

What I did find difficult, apart from the poor operation of the Draper ignition light, (its ceramic magnet's sensing of the pulse in the plug lead was erratic at best, and absent at worst), was the fact that I've read of the importance of getting my eye level with the inspection hole.
This afforded me a splendid view of my 40mm Bing, so I had to compromise as best I could.

The upper, of the two lines below OT, was level with the mark, so I reckon when last I timed the ignition, I was working on the wrong information -- unless there's some way the timing can "creep."
The end of the camshaft, where the sensor fits, is decidedly gnarled, but I'd expect any movement to retard the timing ?
The tappets are fine, so I don't think I've hammered the valve seats, and no pinking has been evident, so I'm hoping no damage has been done ...

I was unable to get any strobelight at 3,500 rpm, so until I get access to a proper light, I'll leave things as they are. A test ride confirmed a much happier and more relaxed engine, though the carbs still need to be balanced, and the mixture weakened slightly.  

The main lesson here for me, was that the Draper light is a waste of £23.50.

Rotifer.

[Barry]

What I did find difficult, apart from the poor operation of the Draper ignition light, (its ceramic magnet's sensing of the pulse in the plug lead was erratic at best, and absent at worst), was the fact that I've read of the importance of getting my eye level with the inspection hole.
This afforded me a splendid view of my 40mm Bing, so I had to compromise as best I could.

Yes the carbs do get in the way when you are trying to eliminate parallax error. I have flat top Bings so I can just about sight over the top of them. I find anyway that I need to look down slightly towards the imaginary centre of the crankshaft rather than dead horizontal.

Shame about the timing light . I suppose you tried the other 3 plug leads. Assuming it's not actually misfiring I wonder if temporarily opening up the plug gaps would help to force a stronger spark and therfore a stronger signal to the timing light pickup.

[Rob Valdez 79 R65]

I have heard that it can be a good idea to use an independent 12v source for the timing light, rather than power if from the motorcycle battery.

You might try working next to the car, and using the car battery for your power source.

[Rotifer]

You're right Barry, line of sight is a compromise. Looking to the crankshaft centre, OT was just above the notch -- on the level, (guesstimate) it was midway between centre and top.

Spark gap was 25 thou, and as there was no miss, I didn't try other leads. It seemed to work best with the lead pressed tight against the ceramic magnet. I suspect function has been sacrificed for the sake of ease of use.

I agree Rob, a power source that's not part of the system is a must. I discovered that two spare batteries are duff, and ended up using a battery charger as my source of 12 volts.

Then I took my trailer to store it in my mate "12sheds" garden. He was in his workshop, surrounded as usual, by strange ephemera, with a newly acquired electronic singing and dancing frog which lip-syncs to "It's a Wonderful World."  He's stripped off the frog exterior, and has attached an animal skull to the jaws, and is well on his way to a singing dinosaur of truly horrifying demeanor.
Then we lingered over a beer in his kitchen, next door to the barn where until recently, Chinese Triads were growing medicinal herbs ...
Nothing ever happens round here.

Rotifer.