Pazon timing, an old subject. Mk3, 31 degrees at 5000 rpm . Or other ideas ?

Is this correct. 31 degrees at 5000 rpm ? I've always set it at 3000 but noticed today that it went above 31 once the rpms increased above 3000. ? Definitive answer ? Roy. Probable different answers methinks. Roy.

"27. Start engine and run for 4-5 minutes to warm up. Using a white light
strobe, time the engine to the full advance mark (previously used in step
19) with the engine running up to 4000rpm. If running in, you may strobe
time at 3000rpm to the full advance figure less 2°."

Has this chart, just found, have any accuracy ! Seems about right, or is it ? About 32 at 5000 ? When set by the red dot at 31, it was reading tdc at 750 rpm tickover. Easy for starting ! Roy.

Wow, there's a fair bit of variation at tickover going on between those ignition systems. 1 to 16 degrees of advance. May explain why some bikes start easier than others. Does anyone have the factory points / advance unit curve?

Mart UK said:

Wow, there's a fair bit of variation at tickover going on between those ignition systems. 1 to 16 degrees of advance. May explain why some bikes start easier than others. Does anyone have the factory points / advance unit curve?

Click to expand...

It's the curve marked AAU. (automatic advance unit)

Mart UK said:

Wow, there's a fair bit of variation at tickover going on between those ignition systems. 1 to 16 degrees of advance. May explain why some bikes start easier than others. Does anyone have the factory points / advance unit curve?

Click to expand...

There’s a massive difference all the way through the rev range !

I’ve pointed this out before, such a huge difference does make something of an irony of the level of importance most of us place on super accurate setting of the ign timing cos no matter how accurate you set it, do you really know what it’s doing at any point in time !?

The specified ignition advance should only apply when compression ratio is standard and you are using specified fuel and jets. If you change compression ratio, fuel type or ignition advance, you need to rejet to suit the change. For a road bike, it might only involve raising or lowering the needles one notch - the main jets are should be rich enough to cope with a slight increase in ignition advance.

acotrel said:

The specified ignition advance should only apply when compression ratio is standard and you are using specified fuel and jets. If you change compression ratio, fuel type or ignition advance, you need to rejet to suit the change. For a road bike, it might only involve raising or lowering the needles one notch - the main jets are should be rich enough to cope with a slight increase in ignition advance.

Click to expand...

With my bike, I run methanol with 34 degrees ignition advance. One thing I really avoid is moving the trigger of my Boyer. Jetting the carbs is tedious.

The AAU advance curve is optimum for a street engine. An ignition with advance NOT all in by 3000 RPM is giving up some midrange grunt compared to the stock (AAU) curve. For kick starting, the less advance at very low RPM, the better. When we built competition engines (auto) we would set the static timing at TDC to ensure an easy first-start for the initial cam break-in. Virtually all conventional (non-computer controlled) 4 stroke engines that operate in the rev range typical of these motors work best with all advance in by around 3000 RPM or less. Heck, a Honda CB400F motor from 1976 with a redline of 10,500 RPM has an "all-in" advance spec of 2500 RPM!

Just my 2 cents, but I never set the timing over 28 degrees on a MKIII. Too much chance of it kicking back and harming the starter mechanism. You'll never feel any loss in performance.

I see from the chart that the pazon unit gives a bit of a margin for starting at tdc. I'm going to set it at 2 to 3 degrees at 750 rpm and see how it feels . Should minimise chances of backfire ? If I understand it correctly ! Roy.

The pazon curve is not the best for the commando, 5000 rpm peak advance is 2000 rpm too high. The Tri Spark and digital pazon are better for advance curves.

Keep it at 27 or 28 degrees with modern fuels.

"Keep it at 27 or 28 degrees with modern fuels."

Interesting... I've found via testing that on modern fuel my (stock) 850 Commando engine performs best with 32 degrees of total advance using the OEM advance curve (originally determined with the OEM points/AAU now with a Trispark).

But to determine optimum timing requires testing on the individual engine involved. Identical engines can vary in their timing "preferences." Factory timing is conservative to allow the engine to function properly on a variety of fuels and account for internal engine variations due to factory tolerances. Also, if looking for maximum timing/power, the fuel used to determine that (brand/octane) should be used from that point forward.

FWIW, in years of building performance/competition (car) engines we almost never found an engine that performed best at factory timing specs. ALSO, we found some pretty extreme variations in HP between identical stock engines. One that really stands out in my memory were two stock engines, advertised as 425HP. One produced 430HP on the dyno; the other identical engine produced 510!!!!

Did not FE mention at some point in the past that the dyno didn't seem to notice much of a difference in timing settings when it comes to power? For street use kick back and piston holing would be the primary concerns?

On my Pazon I see advance up to 5000, set it at max advance, so at 5000. Just like Pazon say, I think! No, I haven't dragged out the instructions, but I base what I do today on what I settled on at first installation!

I tend to run a couple of degrees less than the 31 for a number of reasons, including long rods, but I have run 30 to 31, which will be absolutely fine.

And yes, FE did recently share the results of dyno testing that indicated you are unlikely to see much performance difference between maybe 27 and 32!

Set the timing at 750rpm /3° . It now starts immediately on the button ! A first in 22 years. No chewing of sprag after 4 goes, (so far) . It has now had about 20 !! Engine sounding sweet and sits at 29° at 4000. Used a cheap (£8.00) rev counter left after working on small strokers some years ago. Dindn't have to get off my stool so often. So far so good. Roy.

"And yes, FE did recently share the results of dyno testing that indicated you are unlikely to see much performance difference between maybe 27 and 32!"

Virtually all of my serious engine building experience (shops with dynos) is with auto engines. A typical US V8 of the 300-350 HP factory rating often gained 20+HP with optimum timing over factory timing. Higher HP factory engines would gain more though the percentage improvement was about the same. I haven't seen FE's results but on a 750/850 Commando I would think 2-3 HP is possible. Think of the bragging rights..."Your Commando makes 47HP on the dyno? Heck, MINE makes 49!"

I think if you get the timing ‘out of range’ you’ll see a drop off that drops off exponentially the further you move away.

But on the dyno, with Triumph twins, triples, Nourishes and Nortons, I have persoanlly found that ‘the range’ is a good few degrees. Meaning that a couple of degrees either side of ‘nominal’ just doesn’t show up on the dyno. But, of course, you do have to know what ‘nominal’ is for your set up.

My other controversial point about timing is the randomness of the ign curves. Depending on which system you have, you can be miles ‘out’ of where you thought you’d be after setting the timing ‘correctly’.

Looking at the dynodave graph posted above (where are ya Dave??) at 5000 rpm and above there is 5 degrees difference between the lowest and highest. At 2000 rpm there is what looks like 14 degrees FFS! So two identical bikes with their timing set perfectly, and exactly the same, could be running wildly different actual timings riding side by side on the road.

If precise ign timing mattered that much, only ONE of those systems would be ‘right’ and the others would run like shit! And by now, we’d all know which one that was.

Of course, this is NOT to say that ign timing doesn’t matter. Experimenting to see what suits your bike best (where ‘nominal’ is) can’t be a bad thing. But I’d eat my Shoei if anyone with a stock ish Commando got a meaningful power increase by tweaking their timing by a couple of degrees from the recommended setting.

Conversely, my own personal experience is that these old / crude engines need the biggest, most powerful spark we can reasonably provide, this can yield tangible benefits and is therefore more important than choosing 28 or 30 degrees of advance.

FWIW my own preference is Tri Spark with the high output coil sold by cNw.

And ‘nominal’ is unlikely to be far away from these figures (courtesy of Mr Maney)…

Fast Eddie said:

I think if you get the timing ‘out of range’ you’ll see a drop off that drops off exponentially the further you move away.

But on the dyno, with Triumph twins, triples, Nourishes and Nortons, I have persoanly found that ‘the range’ is a good few degrees. Meaning that a couple of degrees either side of ‘nominal’ just doesn’t show up on the dyno. But, of course, you do have to know what ‘nominal’ is for your set up.

My other controversial point about timing is the randomness of the ign curves. Depending on which system you have, you can be miles ‘out’ of where you thought you’d be after setting the timing ‘correctly’.

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Time for torque, jet for horsepower. I have very little dyno time, just once for a Triumph race bike. Timing assumptions minimally impacted though I moved from 39 degrees to 37.

The Pazon curve is odd, and it more suited to a bike revving out to 7500 rpm or higher, though I have to admit I am not sure I would want to run it on my Triumph. The Tri Spark is a good middle road and up until the norton unit failed I have not had an issue with them. The same one on my Triumph from 2011 is still going. The norton Auto advance curve really is the best option out there. I am running a static trigger off the auto advance and it really woke up the mid-range over the pazon.

Also after seeing the photo above I would highly recommend a Tri Spark over a Pazon even more when running a single carb.