OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines orange spark

Hi gents, i thought i would ask about orange spark from the spark plug and what the cuases may be(blue is gold i take it). I have clamped a new plug to the motor frame and turned over the engine. I get an orange spark. What are the causes?

I have a magnetron retro fitted(you can see the cut wires underneath the flywheel) to my 80202 B+S and have tested the HT lead to frame = 2.6k ohm.I did follow the OEM checklist and I do think the magnetron might be failing in the triggering/primary coil circuit with the darlington transistor bridge as the kill switch wire is disconnected yet, the tab is grounded to the frame.

Thoughts?

Hi elevatorman,

I'm no engine expert.
However, I did find an interesting article (from Briggs) about spark colours:-
Myths about Spark Colours

All very interesting.
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JACK

Wow CyberJack that made for a very interesting read. Thanks that helps me a lot better to understand,cheers.

Hi CJ, yep thats the article i read but every lawn mower man i know swears by the theory of the need for a blue spark so that's why i thought id ask!!

I've read that Briggs article before. Personally I think it is only partly correct. Yes, the nature of the gas in the spark gap can change the spark colour. However the spark colour does indicate the temperature of the gas in the spark gap. Observing the colour is a standard way of measuring that temperature (known as the "colour temperature", because optical instruments are the most commonly used and convenient way to measure it). So, a blue spark is a hot one, and a red spark is a cool one. An orange spark in my experience so far is always an inferior one, but I believe Briggs when they say that having the wrong gas in the spark gap can reduce the spark temperature.

Yes I have to agree with grumpy here.As I have had this very problem before.My VC-160 Auto Drive Mark IV,it had an orange spark and it just would not run.I just went and changed the whole ignition and got a blue spark.It ran like a dream and is still running today the same way.Still very interesting reading,but to call it a wives tale.Hmm it has worked for me.

Ok thanks gents. Does anyone know where you might find a replacement magnetron new or old for sale for a 80202?

Hi all,

Yes, it's nice to have a critical expert on these forums who knows the theory. Thanks Grumpy.
I was always told a blue spark was better than an orange one...

Is there a direct relationship between the intensity of spark and the colour?
Also, some mechanics also listen for the 'sound' of the spark. A 'snap' is good?

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JACK

In principle, Jack, the temperature in the spark gap should reflect the intensity (rate) of energy discharge, which will be voltage times current. However there can in theory be complications. A more conductive gas (compared with pure ionised air) might result in a lower voltage and higher current, with less ionisation, meaning a partial short circuit compared with having to discharge the energy through ionised air. I speculate that this is what the Briggs note refers to when it says that the spark will be orange in the presence of sodium.

In the old days people used to do a sort of party trick, striking a continuous arc between two electrodes then blowing compressed air across the gap. The arc would then take a long curved path across the gap, following the position of the displaced ionised air. This is because it takes a lot more voltage to strike an arc through cool air, than it does to maintain one through ionised air.

I don't have any data on colour versus intensity: is an intense arc white or blue? I think the answer is our eyes can't see far enough into the violet to observe the true colour anyway.

With regard to the sound of a spark, in my experience arcs are noisy, and an arc welder at high current is a whole lot noisier than a spark plug. For sound to reach us, the spark has to have had some duration. If you integrate voltage times current with respect to time, you have the amount of energy discharged. In other words volts times amps is power, or the rate of energy discharge. Volts times amps summed up over time is energy. Or, volts times amps is power, in watts. Kilovolts times amps is kilowatts. Kilowatts times time is kilowatt hours, which is what the electricity company charges you for on your bill.

A standard Kettering ignition system stores energy in a magnetic field, then with the aid of a capacitor, turns that energy into a spark over whatever duration it takes to use it all up. It is possible to create a much hotter spark with a lot less energy, just by reducing the duration of the spark. More kilowatts will flow, but very briefly. That is what a Capacitive Discharge Ignition does: it produces a very intense, very brief spark compared with a Kettering system. Which is better? Depends what you are trying to do. Combustible gas is ignited by raising the temperature of a large enough amount of gas, to a sufficient extent. CDI is marvellous for firing across fouled plugs, but it is poor for igniting lean mixture, because of the short duration.

Getting back to your point, I think the amount of sound you get from a spark depends on the energy discharged rather than the rate of discharge (the spark intensity). My recollection is that CDI sparks are quieter than Kettering sparks - but I haven't really tested this.

I'll repeat a point I've made in another thread. My father and uncle, a pair of vintage racing car enthusiasts, had a problem choosing an ignition system for an old 2 stroke that was very difficult to keep firing because it fouled its plugs. They tried Kettering and found it ran very well until the plugs fouled. They considered CDI but were alarmed to find that if you put a sheet of paper in the spark gap and continuously triggered a spark, the CDI system would just burn a microscopic hole in the paper. The original Kettering system, in the same test, immediately set fire to the paper. So, you can't have it both ways. They experimented and found a CDI system that blackened more paper than the other CDI system they tried, and settled for that. It worked well enough: they never fouled another plug.

Thanks Grumpy for the lesson. I thought i was back at trade school haha. Just as an update i removed the engine from the frame and tried to start it. i finally got it started but i ran out quickly and it was rough as guts. I tried this with the throttle cable off and maybe thats not a good idea. But i do need to have an idea of the carby and the settings of all the bits and how to tune it. Does anyone have a picture of this? I did try to get a manual(subs paid) but we had download issues then and all i got was a parts lists. Can anyone help?

Deejay i will fit the clutch assembly while i have the motor off the frame.

Thanks in advance

EM.

Let's do this one step at a time, elevatorman. First, have you tested the spark? You said at one point that you had the Magnetron tab grounded. The only tab I know of, is for the kill wire. If you grounded that, you obviously would not get any spark whatever.

Can we have a couple of pictures of the 80202 please, including one of the Magnetron installation?

Hi grumpy thanks for the reply. I did say i the tab was grounded to the winding but it might be reading thru the low ohm primary coil. I am yet to find an exact print for the magnetron which includes the grounding tab and switch included. Anyway i reinstalled it and tested the spark, with the grd wire off, and this is when i got the orange spark. I have just retested the spark to frame with the kill wire active to grd and there is no spark which is good. I am still a little dubious as to how good the magnetron is but we will see.

As i said i did get it to start but i think my carby needs to be tuned correctly which why i wanted some help with it. Here are some pics of it. I am still unsure of the choke action and how it is implemeted as i have just a normal speed control level so any pics would be great.

First, how your choke works. You have a Choke-A-Matic feature on your Pulsa-Jet carburetor. Here is how it should be set up:

It automatically pulls out the choke when you set the speed control to the choke position, and opens it when you move the speed control back to the maximum speed position. Please operate the speed control through its full range and check that this is happening correctly. If it is, please report that, and also describe any shortcomings in the way the engine starts, runs, and varies in governed speed when you operate the speed control.

I'm not an SB45 guy, but I'm used to them having a remote control fitted so you can adjust engine speed, choke, and kill switch from the handlebar. Your machine does not appear to have a remote control connected to the governor:

Note that this illustration shows a Vacu-Jet, so the choke pull-handle runs horizontally instead of vertically. Also, this version does not have Choke-A-Matic. However the purpose of the remote control is to operate the speed control lever, whether it has Choke-A-Matic or not.

Here is an SB45 with the normal remote control fitted:

The picture is of tezza98-tnharris's SB45, shown in this thread:
https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=14957&page=5

Note that like the previous illustration, this one has a Vacu-Jet, not a Pulsa-Jet, so the engine is an 80102, not an 80202, and it did not come with a Choke-A-Matic.

Thanks for the reply grumpy. I have a few questions.

On my throttle control i have basically only slow to fast so when you say choke control when or how do you do this? I think i can only do this when i set the throttle to fast speed. Is this the way to do it?

When you say governed speed do you mean a consistant speed thru throttle range?

You mention that your used to having be able to adjust the speed,choke and kill from the handle bars. When i connect the throttle cable(i will do this and then show a picture) i can do this when connected to the speed control lever arm. Is this what you meant?

Just to let our fellow members know i found this on the web describing how the air and fuel work with this pulsa jet carby.
http://www.compgoparts.com/TechnicalResources/BriggsCarburetors.asp

Grumpy do have a write up also of what all the different adjustments that you can do to tune this carby. I assume the main screw is the air fuel adjustment but what should it be set to firstly? And the same for the throttle cable, should you set the kill first to operate(important) then everything after that. I take it that you can adjust the cable length or even at the handle to calibrate stop to full speed as well? I just want to get a idea of what it should be instead of what it was!!

These two instructions from the manual deal with those questions:



See how you go with those procedures, then we can discuss further steps if necessary. Note that the mission is to set up the carburetor and choke-a-matic. Setting up the remote control then simply involves making the speed control on the carburetor cover its full stroke.

Ok grumpy thanks for that. I will try this and let you know. I have taken some more pics so you know where my throttle cable is and the relevant position at the carby.




Fast speed with the position at throttle.




Stop at throttle.



I just thought this is interesting there is holes for adjustments. What do they do?

Another thing is, is when you cycle the throttle cable it appears as if it doesnt do anything to slowly adjust the speed until the level for the choke action moves? Is this right? I also noticed that there is a hole that goes into the crankcase and i imagine this is where the governor is supposed to be, which adjusts the speed to advance the mix as you go(on other vids i've seen) is this right?

Ok i have another issue. On trying to tune after start there is a big screech. I thought it might be a score on the magnetron(as there is a mark on the flywheel and that i noticed the gap changes minutely so it might not be pure round) but when adjusting the gap a little bigger, then trying again the noise was there again and i think it might be the clutch starter. When you hold onto the square shaft it will move in and out from back to front about 2mill or so. How do you judge whether this is worn or not? The plastic cord wheel looks ok but if you replace 1 should you replace the other?

The first time i tested this(its still running really bad) the squeel was high and bad!!

What do you gents think?

First, there is something odd with your choke rod connection to the choke. If you look at Figure 54 you will see there should only be one hole in the choke for the choke rod. You either have two holes, or the rod is not in a hole.

Second, the engine has an air vane governor, not a centrifugal one. The vertical piece of sheet metal with the row of holes is the air vane. Air pressure on the vane, from the cooling fan, pushes the vane in the direction to close the throttle. Pressure from the governor spring (painted orange on your engine) tries to open the throttle, so a balance is achieved between the two forces on the vane.

You cannot see, when the engine is stopped, what speed the governor is set for. Moving the speed control lever pulls on the governor spring. At first, when the engine is not running, the vane just moves closer to the flywheel fan until it runs out of movement. When the engine is running however, the vane is affected by air pressure from the fan and resists going closer to it.
If you look the upper illustration in Figure 56, below, you will see that your throttle butterfly link goes in the uppermost hole in the governor vane, and the governor spring goes in the second hole. The lower holes are for other engines that use the same vane. Note that the lower illustration in Figure 56 shows the later generation of air vane, which was horizontal with a proper pivot.

sounds like it could be the starter ? remove and clean inside where the balls are (if i'm thinking of the correct starter ) as i didnt see it yet but dont put any lube in there as the balls stick in it . just clean all crud and maybe rust from the shaft . a little spray grease works for me well so far and light machine oil in the small hole in top of starter if all is clean and dry inside , shaft lightly lubed all should be good , deafening screech huh hope it helps


, Dave