Adjustable ignition timing

[Venice Motor Bikes]

It's important to remember that air cooled engines need a certain amount of retard in the timing or the engine will run too hot!
Setting the timing 'by feel' on one of them to where it runs the fastest isn't a good idea.

 

[bairdco]

bigbutterbean, i can respect your opinion, but you know that there are people out there (like me) that just ain't happy leaving an engine alone.

for us, there's no such thing as "good enough."

 

[flybytaco]

I could be wrong about speed and mileage, but a stock setup is still easier to maintain.

I agree I've been running stock setups with bolt ons no internal mods and I'm having way better luck theese days with good runners

 

[flybytaco]

It's important to remember that air cooled engines need a certain amount of retard in the timing or the engine will run too hot!
Setting the timing 'by feel' on one of them to where it runs the fastest isn't a good idea.

also agree..

 

[FlyGuy]

From what i undersand....

Adjustments in timing advance or retard have the most impact on the temperature of the exhaust gases that exit the exhaust port.

Senario 1 Ignition around 2.5mm before TDC..... (Retarded Ignition Timing)
The combustion process has more time to complete before the exhaust port opens. The hot gas has more time to transfer heat to the piston cylinder and head. So the exhaust gas comes out of the port cooler.

My question is dose this mean the engine head cylinder and piston are actually getting hotter? Since more heat is being transfered to them?


Senario 2 Ignition around .5mm before TDC..... (Advanced Ignition Timing)
The combustion process has Less time to complete before the exhaust port opens. The hot gas has less time to transfer heat to the piston cylinder and head. So the exhaust gas comes out of the port hotter.

My question is dose this mean the engine head cylinder and piston are actually running cooler? Since more heat is being transfered out the exhaust?


The secret of the story..........

In pertaining to the Expansion Chamber this could be a benifit.
Hotter gases move faster.
Cooler gases move slower.
The speed the gases are traveling impacts the powerband of the pipe.
Slower gases put the powerband in lower rpm.
Faster gases put the powerband in higher rpm.

Look at these CDI kits.
Says universal.
Can we use these????
Horse Power Ignition

 

[corgi1]

I would think the exhaust gas would be just as hot ,it was just in "contact with the head cylinder and piston for a longer duration thus allowing the transfering of more heat"(it is still a ball of fire when it leaves the cyl.maybe even hotter as a complete(more time to) burn),the expanction chamber can be lenght altered to adjust for the fuel/power waste (the blow back thing exp chambers do packing the escaping mix back into the chamber befor the port closes)

 

[FlyGuy]

I'm positive the exhaust gases out of the port will vary in temperature with ignition timing. The magic is with a dual curve cdi that advances and retards the timing vairably you flip a switch to changes curves. Based on that you can actually gain a broader rpm range where the pipe hits. Extending that seat of the pants pull of the pipe.

 

[ferball]

Just a quick idea for the more electrically inclined than myself, but here is a concept just based on a quick review of how a CDI functions. Dual curve cdi..... There are two wires coming off the engine into the CDI my understanding is that one of these wires carries the "signal" from the "hall sensor" which fires the spark. What if we could introduce an intermediate circuit that is manually controlled that retards the "signal". Slow it up some how with resistors or something. This would offer a cheap dual curve bolt on for standard engines.

 

[leezy_1]

errr, think you can make a good clear step by step video no this...

 

[ferball]

Well I did a lot of reading on HT timing last night, it appears that the "signal" is just a portion of the sine wave. In one of the post it was mentioned that adding a small resistor between the CDI and blue wire retards the timing slightly. I am planning on experimenting with this after I get my bike up and running. It would be easy to wire a switch that could "activate" the resistor circuit to retard timing at certain speeds. It would be like cool like a nitrous switch or something if you could get it to work right.

 

[corgi1]

That sounds good

 

[FlyGuy]

HPI makes a Dual Curve Cdi it cost 50 bucks.
You just flip a switch to change the ignition timing curve.

Here is the graph for the coil pack.
Click it for a bigger view.
You can see the timiing changes with RPM.

 

[FlyGuy]

OMG

Here is every bit of info about the HT ignition that exist straight from Grubee.

Great Magneto Mystery

 

[ferball]

OMG

Here is every bit of info about the HT ignition that exist straight from Grubee.

Great Magneto Mystery

Great Stuff thanks for sharing it.

 

[maintenancenazi]

Wow, great read here. Think I will do some experimentation! Oh, sorry for the old thread bump!
Peace out.....

 

[biknut]

OMG

Here is every bit of info about the HT ignition that exist straight from Grubee.

Great Magneto Mystery

According to this the ignition fires at 15 degrees BTDC. Jim said 12 degrees is good too.

 

[chris619]

can my bike still run without the split collar? i found out my engine didnt come with one. and im having problems starting.

 

[biknut]

can my bike still run without the split collar? i found out my engine didnt come with one. and im having problems starting.

I think you could probably use a star washer.

 

[chris619]

can that be one reason my bike wont start?? what does it look like? where can i buy one??

 

[biknut]

can that be one reason my bike wont start?? what does it look like? where can i buy one??

Check your timing. When the piston is TDC the keyway should be at about 2 o'clock.

This is what a star washer looks like.

http://www.primefasteners.com/pages/catalog/washers/star.htm