hows my tune ???????????????????

[Skyliner70cc]

The problem is you are tuning your engine for kph, you need to tune for mph, it makes all of the difference in the world!

[Fabian]

Scroll down to Number 38 for info on setting up an EGT on a motorized bicycle

[Fabian]

Simply playing around with jets can be problematic because it doesn't take long for the I.D. threads to wear. This allows fuel to potentially leak along the threads making the mixture richer than the jet number may suggest.
I have been through this process and it was the EGT which allowed me to find out why the jetting changes were not doing what they were supposed to be doing.

Once you have an EGT on your bike, it eliminates going on a wild goose chase.
The fast response sensor is brilliant, even allowing you to pick up ignition misfires. Typically a spark plug will begin to misfire before you can feel it and the EGT momentarily drops 3 degrees celcius every time the ignition misfires.

[Fabian]

This also has benefits for diagnosing the rest of the ignition system.
If the spark plug is replaced and the engine is still intermittently dropping 3 degrees Celsius, whilst the engine appears to be running smoothly, you know to look elsewhere along the electrical path back to the magneto (with a multi-meter), before small issues become major issues.

[thearcticfisherman]

I'll have to keep posting this, RUN CLIP AT TOP NOTCH!!! RUN A UNI FILTER!!!! USE A BR9HS NGK PLUG!!!!!!!!

[Fabian]

The ignition system on a Chinese bicycle engine is barely adequate for the job, so placing a resistor spark plug in the way makes things even more challenging for the already weak ignition system.

Please explain the logic of using a resistor spark plug?

[thearcticfisherman]

because you haven't tried to use it yet

[Fabian]

Again, i only ask for you to explain your logic in using a resistor spark plug on an already marginal ignition system.

Try this for a read:


Recently an interesting thread on this newsgroup discussed the relative merits of resistive plugs as used on many Rotax engines.

In order to get to the bottom of this Spark plug vs. resistance story I decided to do some experiments. I am a electronics engineer (when I am not flying :-), so I have the tools for the job.

First a coil was rigged for the job to create the high voltage required for the plugs. I used a standard car coil combined with an electronic interrupter/generator. Spark plugs with and without resistors as well as caps with and without resistors where obtained. The plugs where all equally gapped to 0.4mm. I used a scope to monitor the voltage at the plug tip as well as at the coil (via high impedance probe - scopes are expensive !). The result was quite interesting.

As expected, the voltage at the cable (before any resistor) rises at the same rate regardless of resistance until the point of firing. Thereafter however the picture changes.

The coil generates a certain amount of energy. This energy wants to go somewhere. At a voltage of about 7KV the plug fires (irrespective of resistance). Until that happens NO CURRENT FLOWS. Whether you have resistance or not does not matter. A paltry 5KOhms does not do anything when compared to the nearly infinite resistance of the gap itself (until the plug fires that is).

Once the plug fires the resistance comes into being. The coil cannot get rid of its energy in the shortest possible time due to the resistance.

This reduces current flow in the spark and it takes quite a bit longer until the energy in the coil has expelled itself via resistor and spark gap. This results in a longer spark. However the spark is weaker due to energy loss in the resistor.

The scope shows this very nicely and it also gives reason why the resistor helps to suppress RF. With the resistor changes in the rate of current flow are much less resulting in "flatter" edges on the voltage vs. time curve that the scope shows you. This implies less high frequency components of the signal in the cable feeding the spark plugs.

Conclusion: It is quite safe to insert a resistor. It will not stop the plug from firing at all. High values will however lead to a weaker spark -but it is going to spark, no matter what.

However, contaminate the plug with fuel (even just a little) and a high value resistor will cause the plug not to fire. 10K plugs as are used on some motorcycles now are about maximum I would guess.


So would it be far to say that a non resistor plug like an NGK B6HS or the projector nose version BP6HS would be a better choice for a spark plug when it comes to a marginal ignition system?

I have ordered every single spark plug from the SickBikeParts catalogue and found through trial and error that the most consistent running plug (over time) was the NGK BP6HS and BP7HS.
Surprisingly the thin wire (resistor) platinum spark plugs became inconsistent after a relatively short time with irritating misfires, despite being a better performing spark plug when new.
My oil/fuel ratio is 20:1 and the thin wire platinum plug should be superior in such circumstances, yet it was not the case in practice.

[Fabian]

The big advantage of a CDI ignition system when used on a 2-stroke is it's ability to create a short duration but a very hot spark in an oil contaminated environment, as is the case with 2-stroke fuel.

Adding a resistor spark plug into the system just weakens the short and intense energy delivery; negating the benefits of a CDI ignition system.

[wrongway]

My bike has the bp6hs 10 and a different cdi and coil which a seperate I will go a video tomorrow over the whole bike