He there I was wondering if anyone could shed some light on why my Kazuma 250cc has a weak spark on one cylinder, cyl 1 is fine and does most of the work and cyl 2 is a bit erragular and misfires/cuts out and often on cold starts it wont fire at all.
The bike runs rich and fouls up the plugs which certainly doesn't help but I just cant understand why one cylinder can put up with it and the other cant.
The bike has only done 200 miles so its got me there.
Any help much appretiated.
Cheers
Liam aka NoMudNoFun

 

I'm completely unfamiliar with your quad, so I need some info:

1) Do you have one ignition coil with two spark plug leads coming out of the coil, or two ignition coils?

2) What does your CDI look like? By chance does it look like this (only you will have to ignore the fact the the text labels only specify one ignition coil output....). If it doesn't look like this can you post a link to a picture of your CDI so I can take a look?



3) How are you determining that you have weak spark? Are you actually looking at the spark with the plug outside the engine, or are you deducing this from other data?

If you have two ignition coils, and you have a "wasted spark" ignition system (most common) where each cylinder fires on every stroke (including the top of the exhaust stroke), then I would try reversing the ignition wires. If it is the ignition system then the problem will switch cylinders, if it is engine or spark plug related it will stay with the same cylinder.

 

Hi LynnEdwards,
There are two ignition coils and the cdi looks just like the one your photo shows.
The cylinder would only fire after I cleaned the spark plug, and it seemed to get worse and eventualy I had to clean the spark plug several times and also preheat the plug to get it to work.
The cylinder no. 2 would be very vulnerable to spark plug fouling, after cleaning and heating the plug it would run ok all day but then the next morning it would again not fire.
Anyway, I have replaced the spark plug and it has been running sweet for two days now, maybe that was the problem.
I will keep you posted.
Thanks a lot.
Liam

 

Hi Liam,

A bad plug could very well be your problem. The spark is supposed to jump across the gap, but on a bad plug there may be a weak spot in the internal spark plug path that allows the spark energy to leap to ground at places other than the electrodes inside the engine. And this is more likely to happen on a cold plug then a hot plug. Electrons jump off hot surfaces more readily than cold surfaces, and once the engine starts the electrodes inside the cylinder will be *way* hot compared to any rogue discharge path inside the plug on the way to the much cooler input. All of your descriptions fit your diagnosis so far.

On your CDI, be aware that if you ever have to change it it is *not* the common CDI like the one I pictured. You need a dual ignition coil output version like for the Honda Rebel ("honda rebel CDI" is a good google search term). This is really frustrating to the novice, but there are at least three CDI's out there that look *identical*, yet are totally incompatible with each other:

1) AC powered single coil output CDI (like the one I pictured)
2) DC powered single coil output CDI (12 VDC goes in where AC power normally would)
3) AC powered Dual Coil Output CDI. The second coil is driven by one of the two ground wires depicted in the one pictured above. These CDIs are rarer, and harder to find.

Be careful if you buy a CDI. Make sure the vendor specifies that it is dual output. Keep in mind that many vendors don't have a clue as to what they are selling, and will tell you what they think you want to hear, so phrase the questions such that they are led into a trap - like:

"So this CDI is the same as for a Honda Rebel? And it has one ignition coil output, right?"

If they say yes, walk away. If they say your question makes no sense since Rebel CDI's have two coil outputs then that's a good sign.

 

Hi LynnEdwards and anyone reading this thread,
I have had a whole week of trouble free cruisin in the Kazuma after installing a new pair of spark plugs, but today the problem returned .
It all started when I used the bikes battery to run a small tyre compressor to top up the tyres, it only took like a minute and the air compressor doesnt use much power at all, anyway later I tried to start the thing and it once again only fired on one cyl, this time cyl 1 was dead and cyl 2 was firing, unlike last time which was vice-versa. I cleaned the plugs and it went ok again but later it failed once more while driving down hill, so I did some swapping of plugs and it then ran ok for the rest of the day.
So I was wondering if anyone could reccomend a spark plug that can put up with being run rich, the plugs in the bike are always black with carbon and I believe it would be easier to select a realy good plug (a iridium for example or a plug that burns hotter then the ones that are in it) that can burn up the exess fuel then fix the running rich issue that I have already failed with.
It was originaly running NGK C7HSA plugs.
Does anyone have any ideas?
Much appretiated.
Cheers
Liam aka NoMudNoFun

 

Is this a new quad? You mentioned something about 200 miles...

I'm wondering about something... What would happen if someone took a cheap single cylinder CDI ($10) and tried to use it to drive two ignition coils wired in parallel (the dual output CDI being much rarer and much more expensive)?

Let's do some tests:

1) Turn on the ignition.
2) Set all kill switches to the "run" position.
3) Unplug the CDI.
4) Set your meter to measure ohms starting off on the 2K ohm (2000 ohm) scale.
5) Place the black lead on the negative battery terminal, and use your meter red lead to measure resistance of each pin on the wiring harness connector to ground.

What are the resistances of each pin looking into your CDI wiring harness to the negative battery terminal? That's six pins, and I need six answers. Use the diagram below and give me the resistance of each of those pins to ground. Identify the pin readings by the name in the picture - i.e.

"AC Ignition Power" pin = 1389 ohms (1.389K ohms)

For the two ground pins use "Left Ground" pin and "Right Ground" pin looking at the connector picture. Remember that when you unplug the CDI and flip over the harness connector everything mirror images...

If you measure a low reading close to zero (which you should) then switch the scale to a lower and lower value untill you're reading a value as close to full scale as possible but not overscaling. [Some fancy meters are autoranging, and do this automatically].

Along with values I need scale info too. If you say I got 0.734 that doesn't help me unless I also know where your meter scale was set. It could be 0.734 ohms, 0.734 K ohms (734 ohms), or 0.734 M ohms (734,000 ohms). That's a huge difference.

The question I'm trying to determine is whether you have the right CDI installed. Your symptoms are very strange, and I'm looking for strange explanations. Here is the generic single output CDI picture (all I have) which should not match you CDI pin functions. But use my labels to identify the pins to give the answers...

 

Just wondering I also have a kazuma cougar 250cc that's getting no spark ive replaces both coils both plugs are good but I cant find a cdi that will fit and work anyone know where I can find one