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Misc: Ignition Optimum Kickstart Ignition Advance


Oldhaven

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I'd like to get some opinions about the optimum kick starting ignition advance number for a normal road going twin or Comet. (close to factory size carbs, 7or 8 to 1 compression, 140 to 190 pound 65 to 75 year old kick starter pusher, magneto replaced by a coil system). I know the factory provided the ATD and Lucas distributor which were theoretically set to 4* BTDC static timing, and I have heard this figure repeated many times on this forum and elsewhere.

I am asking since the programmable ignition I am using has this curve as its default setup:

vincent 1.0 first.jpg

It is a multi spark system with three sparks. As you can see, at kick start speeds the first programmed spark occurs at 12 BTDC, the second at 5, and the third at 0. I don't have too much trouble kick starting my Rapide, generally 2 or 3 kicks from cold and first kick when warmed up. I very occasionally get a pop through the carb when cold starting. I can easily change this and I may reprogram to a lower first spark when I get up north to the summer place where the bike is hibernating for the winter, but I hope I can get some opinions about whether it makes any difference that the starting advance at very low engine RPM's is 8* higher than the factory recommendation. I can change that and not affect the rest of the advance curve.

As a related question, what is the average kickstart RPM, given a good stroke with follow through?

We have 3 twins running on this system now.

Ron
 
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vibrac

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12 BTDC did I read that right?
Is that an invitation to kick back, what do others think?
 

Oldhaven

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I think I need to clarify what I wrote above a bit. I can see that it can be confusing. The way this ignition works is that during installation it is timed to TDC with an LED and degree wheel in the normal manner (or at least normal for an electronic ignition). After that when the engine has been put into what you want for a starting position you turn on the ignition and and kick . It will fire at 0*/TDC when it sees it for the first time. After that it goes to its programmed settings as shown in the chart above. I think 12* would be a bit too advanced for that first firing, but it should not kick back at 0*. The ignition will reset to the initial resting state if it sees no motion of the encoder, (if it does not start) and the starting sequence firing at 0* TDC will be re-enabled. I do notice that Pazon and some other starting curves are lower than 12 (about 5*) at starting and low idle and flat up to about 500RPM, so I was curious what your experiences have been.
 
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Vincent Brake

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I use on all bikes a pazon for the last 5 years. The high end one (well..)
And do very rare have a slight kickback, and a bit more a smoke cough from the carbs.
I run with mikunies 28. Bit on the rich side.
And a 1:8 or 8,7 comp.
When cold or damp from overnight i need 2-3 hard kicks. With releasing the valve lifter at the end to start it.
 

greg brillus

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Kicking speed at the engine is around 250 to 300 rpm, the Vincent engine likes around 4 to 5 degrees initial advance. If you run close to or around TDC the engine will be hard to start and the exhaust pipes will get very hot at low engine speed, anymore than about 8 degrees can start to kick back if you are a bit " Limp wrist ed" with your kicking effort. Full advance using modern fuels and normal compression's between 7 and 8 to one ratio I use 34 to 35 degree max, some get away with more, but this could well depend on the fuel used and your local climate. The old school Hemi combustion chambers of all old bikes and modern fuels do not go so well together.
 

Oldhaven

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Thanks Greg, just what I was looking for. I hope to get some dyno time this year to test out a few new ideas. The advance of technology and the availability of programmable ignitions may require some rethinking of old dogma since we have so many options available. I will at least drop the first spark after 0 to 10 BTDC. I wish I could reprogram my personal ignition this easily.
 

vibrac

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I don't think you will get a better summary than Greg's ,every engine is a little different the Dyno or a rolling road is the only way to get it spot on.
Do put an m8 boss on the back side of the exhaust pipes about 10 inches from the ports for a lambs sensor for the testing, stuffing a probe up a dirty silencer is a poor substitute.
 

Oldhaven

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A friend of mine sent me this picture of a temporary adapter he made for a lambda sensor that does not require welding on the exhaust pipes. While not in the ideal location and a bit farther from the port it could even be used on the road.

DSCN3043.JPG

(Later edit---I had a picture of an M8 rivet nut here as an option, but the sensor is M18, so no good for that)
 
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greg brillus

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Hi there Ron, why not just go with what is in the picture.......Just make a short adapter that fits between the end of the header pipes and the muffler. Then just make up a temporary bracket to support the muffler off the right side pillion plate. Most all of these old bikes run quite rich..... and lean off quickly as the throttle is opened, my guess is that it takes a tiny amount of time for the fuel to catch up to the increasing airflow as the slide lifts. They need to run rich being air cooled anyway, but changes in carburetion will show up well using the lambda sensors. If you can change the ignition, you may see some gains there as well, but a dyno wont show the effects of an engine pulling hard up a long hill on a hot day, so be careful what you aim for. Cheers............. Greg.
 

bmetcalf

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Is there much left for the 3rd spark to ignite? Can't hurt and the programmability (is that a word?) is good.
 

Oldhaven

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I read varying opinions on the necessity for multi spark for relatively mildly tuned engines. I do think my exhaust note is a bit crisper and I have a very nice idle with the three sparks. I have heard that from the other users too, and Bill Norton uses one of these on his Comet engined car and likes it a lot. It would be interesting to try both, and would be quite simple to do with the programming software. it can be changed in a matter of minutes while on the bike. If I do use a AFR meter, the change could probably be detected. Here is a graph I just did of single spark and adjusting the initial sparks down to 5* BTDC. ( I can't do that with 3 sparks because there has to be 5* between the spark events so the coil can recover)

single spark.jpg
 

Cyborg

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I'm about to start dabbling in the world of A/F meters. I bought one for the Comet, but haven't had a chance to use it yet so no real world experience to share with you.... but I believe if you use a heated wideband sensor then I don't think there is any disadvantage to being a bit farther down the pipe.

How are you finding that software? I have it and the adapter, but haven't played with it yet. Figure there is no point, because by the time I'm ready to program things I will have forgotten everything.
 

Magnetoman

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but I believe if you use a heated wideband sensor then I don't think there is any disadvantage to being a bit farther down the pipe.
Like the saying about investing in real estate, it's all about location. There's a big disadvantage to having the sensor too close to the end of a tailpipe on a single because fresh air is sucked quite a way back up the pipe on each revolution, negating the meter's reading.

After encountering this problem with a ~12" clamp-on sniffer sold for this purpose for use on multi-cylinder engines, I made a "blanket" from a high temperature silicone material that wraps around the end of a tailpipe and serves as a Bunsen valve to let exhaust out but not let air back in. That system works fine, although I wouldn't trust it to hold at highway speeds. More recently I came into an old Gold Star pipe to which I welded a bung for the sensor allowing me to swap the pipe between my bikes and not have any limitation on the speed.
 
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Oldhaven

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I was following that subject in your Comet Mongrel thread. What AFR system did you finally get?

I think you were leaning towards this one:


Does it also report Lambda in addition to AFR? I'm thinking it may be something I didn't know I couldn't live without, especially if i am messing around with ignition curves. I like the idea of that short adapter. something like this would make it easy:

pipe adapter.jpg

The software is pretty easy to use, and has a nice help file and a new curve wizard, in case you want to start from scratch, though it is faster to just modify an existing curve, saving it as something else. I have done that for single fire and dual fire Vincents. and could send you those by email if you want to play around a bit. You have dual plugs so you may want to modify the curves down to the 20's anyway unless you are using one of those holes for a Compression Release.

Ron
 

Robert Watson

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I have an Innovate tailpipe sniffer (A/F) that we used to try and sort out a very rich Comet some time ago, and within a short while we had it to a very reasonable tune. I tried it on the TTR but the pipe was wrong and had some much turbulence at the end that I could not get any reading. Maybe this summer I will try it again, although on a twin two right in the pipes with readouts on the handlebars has been done around here on a couple of bikes with good results. If you zoom in on these you can see the setup.20160109_100402.jpg20160109_100415.jpg
 

Cyborg

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Like the saying about investing in real estate, it's all about location. There's a big disadvantage to having the sensor too close to the end of a tailpipe on a single because fresh air is sucked quite a way back up the pipe on each revolution, negating the meter's reading.

After encountering this problem with a ~12" clamp-on sniffer sold for this purpose for use on multi-cylinder engines, I made a "blanket" from a high temperature silicone material that wraps around the end of a tailpipe and serves as a Bunsen valve to let exhaust out but not let air back in. That system works fine, although I wouldn't trust it to hold at highway speeds. More recently I came into an old Gold Star pipe to which I welded a bung for the sensor allowing me to swap the pipe between my bikes and not have any limitation on the speed.
Thanks for that. I was planning on welding the bung in about 5" from the rear of the header pipe. I can easily mount it upstream as the proposed location was just to have it tucked out of sight. As for a Bunsen valve, I'm using (at this point anyway) a reverse cone setup, so that would complicate things. I didn't think about reversion although that is something that I keep in mind while setting up the water cooled exhaust on the barge.
 

Cyborg

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I ended up spending a bit more for the extra digit. Bought it off Ebay, but same price as the site. A far as lambda as well as A/F ratio... it has a 0-5V output for tuning, so I assume yes. Also come with a long enough harness to mount it in a bus.

AF Gauge .jpg
 
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Magnetoman

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I was planning on welding the bung in about 5" from the rear of the header pipe.
For what it's worth, the photo shows where I welded the bung on my extra Gold Star pipe. The sensor shouldn't be too close to the head (because it could get too hot) or too close to the end of the pipe (because of the fresh air. Also, it needs to be toward the top of the pipe (so water condensation at startup won't hit the hot sensor), and somewhere out of harms way. The location I picked satisfies all of those constraints. Although it makes no functional difference, for aesthetic reasons I took a little extra time to make an angled adapter piece between the bung and pipe so the sensor would be vertical.

Since Oldhaven asked about A/F meters and Robert mentioned 'Innovate', I use Innovate's portable LM-1 meter. The company replaced this with the LM-2 model in 2008, but haven't make any changes since then. I mention this because a larger company acquired Innovate c2010 and as best as I can determine there haven't been any improvement to their portable A/F meters in a decade, which is nearly a century in electronics-years. Although I'm happy with the performance of my LM-1, and it's possible the decade-old LM-2 may be as good as anything else currently on the market, if I were in the market for a portable A/F meter today I would research all the alternatives before buying one.

As an aside for any LM-1 readers looking at this post, I hadn't used my LM-1 with my current laptop and when I recently did I discovered to my chagrin that the latest 3.37 version of the Logworks software for it has a glitch that won't let me transfer saved data from the meter (the program crashes when I try). Innovate's technical support was completely useless, leaving me to deal with this myself. Luckily, I had a copy of the installation file for 3.01 on a CD and, despite Vista having been the version of Windows when it was issued in 2009, it installed on Win10 without any error messages and works.

There are several (big) advantages to a unit that has several inputs and also logs the data for later study. I use mine with a tachometer input along with a (universal) throttle position sensor I made based on a potentiometer and AAA battery. Looking at the logs in the comfort of my home, rather than trying to memorize a few numbers as I fly down the road, lets me see see what is happening with the A/F ratio at various throttle positions, as well as see transients when I, for example, slam the throttle open (it records data at 12 Hz).

26747
 
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Cyborg

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I appreciate your guidance. Any chance you could post a photo of the bunsen valve?
At the risk of sounding like one of those infernal rivet counters, shouldn't you have a 1 1/2" GP on there. RRT2 stamped on your gearbox? Just jealousy on my part...
 

Magnetoman

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I appreciate your guidance. Any chance you could post a photo of the bunsen valve?
At the risk of sounding like one of those infernal rivet counters, shouldn't you have a 1 1/2" GP on there. RRT2 stamped on your gearbox?
I'll see if I can find a photo but, if not, take one later today.

That Gold Star is actually one of 365 U.S.-only 'Competition' models and has the stock SCT gearbox. However, since I have it configured with rearsets I replaced the kickstarter with one from an RRT2 to get the lever out of my way. Its GP is in a box because it's more fun to ride a motorcycle that actually idles... That's a 1036 Concentric on it now.
 

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