Hi Forum, I have a Chinese 300cc 4x4 quad bike that has no spark. The quad is sold here in Australia under the brand 'Atomik' but it is also known elsewhere, as a BuYang FA-H300.

Firstly, the majority of the electrics are working. The starter motor cranks, the lights, indicators, instruments, horn etc. all work fine. The battery is less than a year old and holds charge ok. It seems like the problem is limited to no spark.

The quad's ignition system seems to be a bit non-standard and I haven't had had any success getting information or a wiring diagram for it. The main difference from typical CDI systems is that the stator doesn't have the typical 'exciter' + 'trigger' coils. It has two wires from the stator to the CDI unit, but both wires are connected to a single coil that has a resistance of 200Ω and both wires show open circuit to negative/earth. The other anomaly, that I haven't come across before, is the ignition coil has two wires connected to it, apart from the plug lead. One wire is Red/White and is connected to a 6.8mm spade terminal on the coil and has +12V when the ignition switch is on. The other wire is Black/Yellow and connects to a smaller 4.8mm spade terminal. This Black/Yellow wire runs back to the CDI unit.




Resistance readings of the coil are a bit confounding. The two low-voltage wires and the spark-plug wire, are all open circuit to negative/earth. Resistance between the Red/White and Black/Yellow wires is 4.4Ω



Resistance between the spark-plug wire and the Red/White is the same as the resistance between the spark-plug wire and the Black/Yellow wire. 4.7kΩ



I don't really understand how I can get these readings unless there is electronics in the coil.

If anyone can shed some light on this ignition system, I would be extremely grateful.

This is the style of CDI unit I have.






There are also a couple of components I am unable to identify. Does anyone have any idea what these are?






Sorry my second only post is a massive "gimmee", but I have been trying to sort this out myself and I'm stumped. I'm hoping you knowledgeable people on this great forum can steer me in the right direction.

 

There are DC and AC CDI's, do a google search as there are ways to tell the two apart, hope this helps.

 

Thanks mate, that did help a bit.

It looks like I have a DC ignition, based on a TPI (Transistor Pointless Ignition) system.

The 8-pin TPI ignitor unit seems to be common in older Yamaha and Honda motorbikes.

As I haven't been able to troubleshoot properly, I'll probably just start replacing components blind. The easiest component to source is the ignitor. The 2-wire coil has been a bit harder to find.

 

Sorry, I edited the two ignition coil resistance diagrams, but that has broken the links in my first post, and I can't edit it now.

Here they are again.

Red/White to Black/Yellow



Spark-plug wire to Red/White and Spark-plug to Black/yellow

 

I had a Chinese quad that went through a bunch of the DC CDI's. Each time it stopped running I put in another CDI and it would run awhile longer. If you put in an AC CDI ( if it takes the DC) it will instantly go up in smoke, ask me how I know

 

Well I finally found a wiring diagram for my quad's clone (BuYang 300 4x4) and it looks pretty close.

So it seems like I have a DC CDI system, and I may have a faulty ignitor.

The readings on the coil make a bit more sense now. I realise the circuit from the spark-plug wire to the black/Yellow wire has both the primary and secondary windings in series, but the meter is only 'reading' the high resistance of the secondary winding. So both readings from the two wires look to have the same high resistance of the secondary winding.

My two mystery components appear to be the speed limiter and the "Freezer Proof Unit" (a tad superfluous here in tropical Australia)

Is there anybody that can tell me the relationship between the gear-shift Up/Down switches and the speed-limiter?

Also, does anyone know the principle behind this type of DC CDI system? Does the Ignitor unit simply pulse the negative to the ignition coil, similar to points? Or does the Ignitor raise the pulse voltage above 12V, across the primary winding of the coil?

BuYang 300cc 4x4 Wiring Diagram