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ignition timing #417635
02/08/12 6:09 pm
02/08/12 6:09 pm
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gastonia .. NC
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limeyrider Offline OP
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Finally getting around to the ignition timing .. having read some horror stories about holed pistons etc., and not wanting that experience. Can one .. or more.. of the knowledgeable fellows out there offer some guidance?.
Best way to check mag. contacts opening?.. cigarette papers are scarce these days!, buzzer box?.I will be using a degree wheel and finding TDC in the prescribed way.
Appreciate any and all help,thank you.
James

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Re: ignition timing [Re: limeyrider] #417637
02/08/12 6:25 pm
02/08/12 6:25 pm
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Magnetoman Online content

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Originally Posted By: limeyrider
Finally getting around to the ignition timing .. having read some horror stories about holed pistons etc., and not wanting that experience. Can one .. or more.. of the knowledgeable fellows out there offer some guidance?.
Best way to check mag. contacts opening?.. cigarette papers are scarce these days!, buzzer box?.I will be using a degree wheel and finding TDC in the prescribed way.

A buzz box, or equivalent, is by far the easiest as well as best way to set the openings. The ramp on the magneto cam is nearly 0.002"/degree, which means if your cigarette paper is 0.002" thick you will be off by a degree. Also, pulling cigarette paper from between the points in a reproducible way isn't the easiest thing to do anyway.

If you put an ohmmeter across the points the reading will change from 0 ohms when they are closed, to 0.5 Ohms (the resistance of the primary coil) when they open. Clearly, not an easy change to detect. But, resistance is the wrong electrical property to measure. The inductance L changes from ~0.6 milliHenry when the points are closed to ~4 mH when open. That factor of ~10x is the basis for the operation of a buzz box, which is an oscillating circuit. When L changes by 10x so does the pitch of the audio output.

Rather than a buzz box, an inexpensive inductance meter can be used. More on this if there is any interest.

Re: ignition timing [Re: Magnetoman] #417670
02/08/12 9:52 pm
02/08/12 9:52 pm
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Farmington,Connecticut,USA
JBMorris Offline
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Originally Posted By: Magnetoman
Rather than a buzz box, an inexpensive inductance meter can be used. More on this if there is any interest.

Yes there is interest here,
Static timing to be sure.
Somewhere was a reference to a "Factory" buzz-box to set timing?

Last edited by Brien Morrissey; 02/08/12 9:52 pm.

1978 Bonneville T140V PX
Re: ignition timing [Re: limeyrider] #417672
02/08/12 10:25 pm
02/08/12 10:25 pm
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new jersey usa
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pushrod tom Offline
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Not to sound too weird, but, I have used a timing light to set my Goldie. If you can lock the degree wheel to the big nut on the crank and also have a well fixed pointer, then you can set it up static, start it with the primary cover off and read directly with the light. At least then you know where to begin tuning. PRT

Re: ignition timing [Re: JBMorris] #417680
02/08/12 11:28 pm
02/08/12 11:28 pm
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Originally Posted By: Brien Morrissey
Yes there is interest here,
Static timing to be sure.
Somewhere was a reference to a "Factory" buzz-box to set timing?

Originally Posted By: pushrod tom
Not to sound too weird, but, I have used a timing light to set my Goldie. If you can lock the degree wheel to the big nut on the crank and also have a well fixed pointer, then you can set it up static, start it with the primary cover off and read directly with the light. At least then you know where to begin tuning. PRT

The thought of myself keeping a Gold Star running while a big disk is spinning on the crank with gears and chains lashing about, and at the same time reading a non-vibrating(!?) indicator to the nearest half-degree and adjusting the magneto, makes me dizzy. Anyone who can do this deserves my admiration.

As for inductance, take a look on eBay for a Newcason 4070L LCR meter. You can get one for only ~$20 and it will do several useful things for you, including telling you without ambiguity when the points open. If you get more serious about electricity, there are better (but more expensive) instruments to buy, but this one will do the timing job just fine. Set on its 20 mH scale, it will read ~0 when the points are closed, and will jump to ~4 the moment they open. The only advantage a much more expensive buzz box has over it is you don't have to look at the scale to know when the points open. But, compared to dodging flying clutch plates and spinning disks, looking at a scale is child's play.

A buzz box uses the same change in inductance as the meter does to tell you when the points open. A very simple oscillator circuit can be made with an inductor and a capacitor, with the resonant frequency the square root of LC. That circuit is connected to a speaker, and the value of the capacitance is chosen such that the frequency is somewhere in the audio range (50~15,000 Hz). Since the inductance changes by a factor of ~10x when the points open, the frequency changes by the square root of that, a factor of ~3, a difference that is very easy to hear.

I have much more expensive and precise instruments for measuring inductance. But, if you're only going to use a meter to time your ignition, it doesn't matter if the meter jumps to an accurate 4.397 mH when the points open, or it just jumps to somewhere around 4. I actually do use my good instruments at home, but I keep a Newcason in a portable tool bag for use in situations where I want to be able to assist someone on the road.

Re: ignition timing [Re: Magnetoman] #417682
02/08/12 11:48 pm
02/08/12 11:48 pm
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Posts: 977
gastonia .. NC
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limeyrider Offline OP
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Thanks Magnetoman.. truly amazing to have such knowledge.In an article by Hughie Hancox he mentioned attaching a wire to a radio antenna,tuning to station then fading it out as the points gap opened .. or something of that nature.However,I will follow your advice and look on e-bay for a meter.
Thank you again for your help.
James.

Re: ignition timing [Re: limeyrider] #417712
02/09/12 6:33 am
02/09/12 6:33 am
Joined: Aug 2001
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scotland
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I'd say it's worth checking with a strobe on a pointer and mark you make on the sprocket, to see what the timing does as revs go up. The mechanical aspect of points can cause some odd jumps in timing.


Amateur Loctite enthusiast.
Re: ignition timing [Re: triton thrasher] #417741
02/09/12 3:44 pm
02/09/12 3:44 pm
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Originally Posted By: triton thrasher
I'd say it's worth checking with a strobe on a pointer and mark you make on the sprocket, to see what the timing does as revs go up. The mechanical aspect of points can cause some odd jumps in timing.

It's worth mentioning that as the rubbing block on the points wears, the points open slightly later, i.e. the timing becomes retarded from where you initially set it. This is good, because the effect of it is to slightly reduce h.p. rather than punch a hole in the piston. However, if you want your magneto set to a fraction of a degree of that called for in the factory manual (and leaving for another day the effect of modern fuels on the optimum timing), the rubbing block requires some thought.

As I mentioned in an earlier post, the slope of the ramp on the cam in a Lucas magneto is ~0.002"/degree. If we assume the rubbing block in the new set of points installed in your magneto isn't completely smooth and perfectly aligned with the cam (which is a pretty good assumption), it will wear more rapidly at first until it beds in with the cam. Even if you set your freshly-rebuilt magneto at exactly 39.0-deg. (or whatever), if this initial wear is only 0.002", within a few hundred miles it will be at ~38-deg. Because of this, you might instead plan to time your rebuilt magneto pretty well, and save any extraordinary efforts to get it timed "perfectly" only after it has run several hundred miles. Assuming your rebuilt magneto lasts that long...

I realize few people are set up to do this, but after I rebuild one I run it for the equivalent of ~1000 miles at 3500 rpm before installing it in a bike (that's one day in a test rig I built that uses a 1700 rpm electric motor). That not only beds everything in, if no problems develop in the first 1000 miles, there's a pretty good chance the magneto will last quite a bit longer than that without problems.

Re: ignition timing [Re: limeyrider] #417839
02/10/12 1:34 am
02/10/12 1:34 am
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Posts: 50
vancouver, canada
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GS 4112 Offline
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Thank goodness for rolling papers

Re: ignition timing [Re: limeyrider] #420337
02/23/12 12:14 pm
02/23/12 12:14 pm
Joined: Oct 2010
Posts: 35
Melbourne, Australia
nick nick Offline
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Melbourne, Australia
this neat little unit could be of interest to some here, i'm curious to know if anyone has any experience with it?

www.beckelektronika.nl





(click image for link with google translation)

Last edited by nick nick; 02/23/12 12:16 pm.
Re: ignition timing [Re: limeyrider] #420409
02/23/12 7:44 pm
02/23/12 7:44 pm
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Elko, Nevada USA
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Magnetoman ... For many years I've used a timing light checking and setting Goldie ignition timing, as have many others. 'Way back when' I set timing with both paper in the points or home made a buzz box with a 'calibrated' rod down the spark plug hole. That worked ..kinda OK.

With the SRM/Boyer or Crank Triggered Boyer electronic ignition it's imperative you check timing with a properly calibrated degree wheel on the crank and a electronic timing light. Setting the static timing of a Boyer will get you into the ball park good enough to start the engine but not the optimum timing.

With the Boyer Micro Power ignitions on a Goldie the engine needs too be tested at 3000 rpm for full advance. I set my dual plug ignition timing to 36 degrees BTC using a gen-u-wine BSA degree wheel, with an assistant on the throttle and holding up the bike and me with the timing light.

If any of you not done this, here's my method that works well. It's the same old procedure used by mechanics for many many years on all brands of engines from airplanes to farm tractors and even Triumphs. Certainly not my invention!
It's a bit long and mournful, but I'll try to cover everything for those of you who haven't had the fun. Don't forget when you are finnished you can stand back and say,"I did that". It's one of those deals that takes more time to read the procedure than to do the job.

Remove the crank cush drive spring, put a large thick washer on the shaft up against the cush drive cam and sleeve, then the degree wheel, another thick washer and then just snug up the crank nut hand tight. The cush drive cams will now be mechanically locked. But of course with a belt drive pulley there's no cush to fiddle with.

I've made up a pair of heavy welding rod pointers. One bolts to the engine case for bench work doing cam timing. The other pointer is bolted to a pair of the forward inner primary holes setting ignition timing.

Always use a 'bump stop' to calibrate the degree wheel for a dead on TDC '0' setting. A 'stick down the hole' won't get it for this!.
It's a bit fiddly until you get the hang of it. But here's the drill.

With the spark plug removed, put your finger over the plug hole and slowly push over the engine until you can feel pressure. You are now coming up on the compression stroke toward TDC.

With the rear wheel off the floor engage 4th gear. Now with a 'stick down the hole', slowly turn over the engine and find the approximate TDC and slip the degree wheel around for preliminary '0' degrees setting.

Using the rear wheel rotate the engine backwards 10 to 20 degrees. With the bump stop snug in the sparkplug hole, adust the screw unil the stop hits the piston. Note the degrees on the wheel.
Again using the rear wheel rotate the engine back around until the piston again strikes the stop coming up from the opposite direction of rotation. Ideally the degree wheel would read the same as the previous step. But it never does. Now carefully slip the degree wheel to halve the error between the readings. Turn the engine back the other way and compare degree wheel readings. Repeat as required to 'get in the ball park' of near equal readings within a couple of degrees.

Now carefully tighten the crank nut securing the degree wheel. Again rotate the engine forward/back and look for equal degrees when the piston hits the stop. But now bend the wire pointer to indicate equal degrees before TDC as a final touch. Remove the bump stop and replace the spark plug.
You're calibrated!

Now the easy part. With the wheels back on the floor. Hook up your timing light, start the engine and with Her on the throttle, read your timing and adjust as required. With a ET ignition check the timing at idle to insure it's retarding.
There you go, 'Bob's yer uncle'.

I wouldn't bother hoping a cardboard degree wheel will 'be OK', it won't. Motion Pro the MC tool supplier sells a nice steel one that will need the hole enlarged with a step drill bit. You can make a bump stop from an old spark plug body with a threaded in bolt, but why bother, buy a nice one.



Last edited by dave - NV; 02/23/12 11:50 pm.

dave - NV
Re: ignition timing [Re: dave - NV] #420425
02/23/12 9:55 pm
02/23/12 9:55 pm
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Magnetoman Online content

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Originally Posted By: dave - NV
Magnetoman ... For many years I've used a timing light checking and setting Goldie ignition timing, as have many others. 'Way back when' I set timing with both paper in the points or home made a buzz box with a 'calibrated' rod down the spark plug hole. That worked ..kinda OK.

With the SRM/Boyer or Crank Triggered Boyer electronic ignition it's imperative you check timing with a properly calibrated degree wheel on the crank and a electronic timing light.

Now the easy part. With the wheels back on the floor. Hook up your timing light, start the engine and with Her on the throttle, read your timing and adjust as required. With a ET ignition check the timing at idle to insure it's retarding.

I was being a little facetious when I said how difficult this was, but for me it's a two-person job for any bike where I use a timing light; one to operate the throttle and the other to mess with the timing.

More relevant is that I don't use a Boyer or equivalent magneto replacement. I test my magnetos (with auto advance, if they have them) on a modified distributor tester, which determines how they behave as a function of rpm before I install them. Unlike what can be done with a Boyer, I am able to then lock my magneto's auto advance in the fully advanced position and install it on the bike that way. Because of this, just like the proceedure you describe, the limit on absolute accuracy of where the device fires is the limit on being able to determine TDC.

The difference is, unless you have a similar type of distributor tester, you have no way of knowing how much electronic advance a given Boyer will actually give you, so you have to rely on the manufacturer's literature and install it using the static value in the hopes it will be close enough to get the bike started. Because of this, for you a timing light is essential, because otherwise you would have no way of setting it to fire at the hoped-for value when fully advanced. In essence, my use of my distributor tester is the same as your use of a timing light -- I do all the measurements you do, except I am able to do them with the magneto off the bike.

In the end, we both can set our ignitions to fire at, say, 39-deg. BTC to better than a degree. The more problematic issue for both of us, that we haven't addressed, is whether 39-deg. (or whatever) is the value that should be used with modern gasoline. These change their composition, amount of ethanol, etc. a number of times during the year. The change in composition changes the burn rate, and thus a set-and-forget, one-advance-fires-all timing doesn't work like it did with the less-variable fuel available 50 years ago.

In other words, the real issue we face with our bikes isn't so much whether one technique can set the timing closer to 39.0-deg. than another. It's whether 39-deg. is the right value in the first place (and whether, even if it is for "December gasoline," it still is for "June").

Re: ignition timing [Re: limeyrider] #420447
02/23/12 11:46 pm
02/23/12 11:46 pm
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Elko, Nevada USA
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Magnetoman sez ...
In other words, the real issue we face with our bikes isn't so much whether one technique can set the timing closer to 39.0-deg. than another. It's whether 39-deg. is the right value in the first place (and whether, even if it is for "December gasoline," it still is for "June").
..............................................................
How very true! I too am concerned on what is the proper ignition timing with today's fuel. Or for that matter the differences in pump gas between the different suppliers. This is why many/most racers use 'race gas' to eliminate at least the fuel variable from their tuning issues.

We know that ideal timing will result in a 'happy motor' that's making it's peak power. This can be easily tested on a dyno, but only a very few road guys will bother.

Back in an earlier era, BSA and others I'm sure used the open road 'dyno' for this. Here's thier procedure I've read about but not tried.
With the bar manual advance lever at half travel set the ignition timing at the prescibed value. While pulling max revs in 4th gear adjust the timing with the bar lever for highest revs. Leave the control in that position and measure the timing back in the shop. Adjust the lever for full advance and reset the timing for the newly arrived at value.

I use my 'dyno road' hill outside of town for tuning experiments. With my little digital tach hooked up I pass the 'yellow sign' at exactly 5k revs in 4th and wack it on. I then read the revs when I pass the 'blue sign' about a 1/2 mile up the long hill. It's repeatable, seems to work nicely and it's a 'real world' performance test seems to me. (prolly complete with real world NHP troopers too) ooohh


dave - NV
Re: ignition timing [Re: dave - NV] #420470
02/24/12 3:38 am
02/24/12 3:38 am
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Originally Posted By: dave - NV
This is why many/most racers use 'race gas' to eliminate at least the fuel variable from their tuning issues.

While pulling max revs in 4th gear adjust the timing with the bar lever for highest revs. Leave the control in that position and measure the timing back in the shop. Adjust the lever for full advance and reset the timing for the newly arrived at value.

Unfortunately, this problem has so many variables, and changes with time, that I'm not sure there's a realistic way to deal with it, short of either always using race gas from the same supplier, or running a few degrees less advance than what might be ideal.

Your "road dyno" is a fine, albeit time consuming, technique, but even if you determine the optimum timing for Brand X gasoline that you purchased in mid-February, the blend of Brand X sold in a different part of the country (let alone, a different country entirely) at the same time will be different. I'm on a trip right now so can't check the precise number, but the U.S. is divided into quite a few regions, each of which gets a different blend at a given time. So, even if you find your Gold Star works best at 38.5-deg. for a fresh batch of Brand X gas sold today, that information is useful only to other GS owners living in the same region. Also, there's no guarantee the blend sold a year from now will be the same.

This is a tough problem, for which I can't see an obvious solution as yet.

Re: ignition timing [Re: limeyrider] #420488
02/24/12 7:15 am
02/24/12 7:15 am
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scotland
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The rule of thumb on checking timing by hand on the road used to be set timing to what you think is the best figure, at full advance, then retard it slowly with the lever, while travelling at the rev range you're interested in, with the engine pulling hard.

If the engine perceptibly loses power (rpm) with any tiny amount of retardation, then your setting was too retarded. You should be able to retard it and not lose power in what equates to a couple of degrees of retarding.

If the engine gains power when retarded, the setting was too advanced and you are actually doing the test the way Dave describes.

The differences are small, but if you set off on your test run at full advance, you know exactly what your timing is. Timing is liable to move, if dependent on cable and lever from standstill in the workshop, to 100mph on the test track.


Amateur Loctite enthusiast.
Re: ignition timing [Re: limeyrider] #420534
02/24/12 4:46 pm
02/24/12 4:46 pm
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england
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GS DAVE Offline
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england
SRMs electronic ignition that I have fitted to my Goldie recormend 37-36 deg btdc.
Mine is a dream to start so I have never altered the timing, only checked it with the strobe.

Re: ignition timing [Re: GS DAVE] #420683
02/25/12 3:07 pm
02/25/12 3:07 pm
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Magnetoman Online content

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Originally Posted By: GS DAVE
SRMs electronic ignition that I have fitted to my Goldie recormend 37-36 deg btdc.
Mine is a dream to start so I have never altered the timing, only checked it with the strobe.

The correct amount of ignition timing for a given rpm and load is determined by the fuel and characteristics of the specific engine, such as compression ratio and valve overlap, so any recommendation by an aftermarket manufacturer is necessarily general (and, likely, conservative). If the optimum value of advance for your particular engine and fuel were, say, 38-deg., it should run just fine at 36-deg. It's just that it wouldn't be giving you the maximum possible power. If for a different fuel it were 37-deg., you still would be safe having set it at 36. If on the other hand they recommended 39-deg., and you actually set it up at 40-deg. because you didn't take the time to get it spot-on, detonation very easily could end up damaging your engine.

It's always safest to err on the side of too little advance. What Dave-NV and I were discussing wasn't the safest advance to deal with all fuels we are likely to encounter, but rather the advance that gave maximum hp (so we would get 40.7 hp from our Gold Stars rather than settling for a mere 40.1...).


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