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Old 10-20-2013, 07:42 PM   #1
rustygardhouse OP
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1980 R65 timing

I've got a bit of a mystery about the point of full advance on my 1980 R65. The frame & engine match with 6348245 on both. The previous owner has installed a Boyer electronic ignition.

Manual - full advance RPM
Haynes - 3000
Clymer - 3500
BMW - 3000
Original Owner's handbook - 3000
Boyer installation info - 3500

Does anyone know which it is or how I can sort this out?

Thx
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Old 10-20-2013, 11:42 PM   #2
Padmei
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What difference does it make?
I'm no expert but everyone has told me 3K.
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Old 10-21-2013, 12:27 AM   #3
disston
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It's not that important. The advance unit will reach full advance at around 3000 to 3500. Will make little difference. If the unit is broken and it reaches full advance at idle you have a problem and idle will be too high. The engine will likely knock on hard acceleration. If the advance unit does not advance at all or enough you will have poor performance and poor gas mileage.

The ignition timing can be adjusted statically with a test light. This is an initial test and is usually used to get the bike running. After static timing is set the full advance timing is checked and reset if need be. From idle the engine rpm is raised slow enough to watch the timing marks climb in the timing window. They should reach what ever mark is used for your model and year at around 3000 to 3500 rpm and stop there. They should not go higher than the middle of the window even if the rpm is raised above the point they did reach full advance.
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Old 10-21-2013, 01:11 AM   #4
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Original BMW spec for the bean can is it starts at 1500 RPM and reaches full advance at 3000 RPM. If the Boyer gives a choice of curves you could experiment but probably no reason to slow down the advance unless you are getting some pinging.

The Boyer advance curves may not be spot on accurate to 500 RPM in any case.
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Old 10-22-2013, 08:06 PM   #5
rustygardhouse OP
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So..

The 1980 R65 was a cross over year & there are at least 2 different horse powers available. The easiest way to change horse power is to change the carb: smaller carb, less horse power. This way, they don't have to stock different rods, pistons or cams for the different horse powers.

But!

A smaller carb at the same full advanced timing runs too lean so advance timing has to be taken out.

This is not simply rotating the ignition for less timing as that changes the initial timing & the idle characteristics. Thus, the springs or fly weights are changed to reduce the amount of full advance without affecting the idle.

If this was a Ford/Chevy/Dodge, I could just run down to Pep Boys & buy different springs to change the full advance.

Since the initial timing is the same for all but the full advance (expressed as rpm for some reason) is different, knowing which rpm for max advance is important.

Why?

Well, if I have the low horsepower & run full advance at 3000 rpm, the engine will run lean, idle like crap & be doggy in the high revs.

While if I have the high horse power & run full advance at 3500 rpm, the engine will run rich, idle like crap & be doggy in the high revs.

It's a Goldilocks thing: right full advance for the carbs give best idle & performance.

Does this really matter?

I don't remember what the rated horse power of the R65 is (44 hp & 50 hp rings a bell). If I got 2 hp more from the right timing, well, that's significant in a bike.

If Boyer has done their home work properly, the electronically induced advance would be very consistent. It may be 3495 rpm or 3505 rpm but it wouldn't be 3250 rpm.

The problem is that if my bike is full advance at 3000 rpm, I can't just turn the distributor as this affects the idle timing & thus the idle.

This is why I like products like Pertronics; they just replace the points & nothing else so the original timing curve is unaffected.

Why do I think there's a problem?

With a fresh carb rebuild, I timed the bike as per Boyer & it ran like a dog above 4000 rpm. A plug cut showed very lean above 4000 rpm. Upped the main jets one size & the bike came alive. Classic timing curve is wrong for the jet size

I'm sure there'll be LOTS of comments on this...
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Old 10-22-2013, 08:30 PM   #6
pommie john
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If it's one of the old black box Boyers ( as opposed to the newer Red box ones) they keep on advancing to about 5000 RPM. I time mine to full advance at 5000 and let it take of itself at lower RPM.
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Old 10-22-2013, 09:57 PM   #7
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Quote:
Originally Posted by pommie john View Post
If it's one of the old black box Boyers ( as opposed to the newer Red box ones) they keep on advancing to about 5000 RPM. I time mine to full advance at 5000 and let it take of itself at lower RPM.
WOW! Really? Full advance not till 5000 seems pretty radical.
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Old 10-23-2013, 01:22 AM   #8
pommie john
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Google helped me find this for Norton Commandos but I'm pretty sure they all have a similar advance curve. As you can see it keeps on advancing even past 5000.
The analogue Boyer is the dark blue line.

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Old 10-23-2013, 02:57 AM   #9
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Quote:
Originally Posted by pommie john View Post
If it's one of the old black box Boyers ( as opposed to the newer Red box ones) they keep on advancing to about 5000 RPM. I time mine to full advance at 5000 and let it take of itself at lower RPM.
Where does the red ones advance to? I tried mine set to ~3.5k and the bike pinged like mad on mild accel. I've just backed mine off until the pinging practically went away on 97octane.
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Old 10-23-2013, 03:02 AM   #10
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Originally Posted by regomodo View Post
Where does the red ones advance to? I tried mine set to ~3.5k and the bike pinged like mad on mild accel. I've just backed mine off until the pinging practically went away on 97octane.
The red box Boyer is the green line in the graph. I have no experience of them so I can't say how they work on an airhead.

As I said, that graph is a for a Norton. It's quite possible that the red ( Micro Digital) Boyer has a different advance curve for airheads but I'm fairly sure the older black boxes had a similar curve for most of the bikes they were used on.
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