Offset Flywheel Keys

[Donald E. Jones]

I have been reading on some of the web sites about advancing ignition timing with offset flywheel keys. They tell how it is done, but I have not read how to determine which key to use. In other words, how do you figure out how many degrees of advance to put in the engine ? Is it just trial and error, or is there a more scientific method? What amount of advance would be a good starting point?

Don Jones

 

[machinist@large]

I have been reading on some of the web sites about advancing ignition timing with offset flywheel keys. They tell how it is done, but I have not read how to determine which key to use. In other words, how do you figure out how many degrees of advance to put in the engine ? Is it just trial and error, or is there a more scientific method? What amount of advance would be a good starting point?

Don Jones

Are you running a stock engine? Or do you have modifications that we don't know about? As a general rule, a stock engine will run just fine as is; playing with the ignition timing may not make much difference if everything else is factory stock.

Now, if you're thinking about performance modifications, playing with the timing can have some real benefits; the timing changes needed, however will be determined by what you are intending to do.

In this case, we need more information......

Pat

 

[firemanjim]

If its just a yard kart, you dont need to advance your timing. If its a "racer", then yes , a few (5°) degrees advance can be used to "find hidden power"....

 

[mckutzy]

In the same respect, with what typical mods does one advance/retard timing? And what gains/fails for such?

 

[OzFab]

IIRC (which I probably don't) I think 1/16" gives you around 4°...

Advanced timing is good for bottom end power but, tends to lose the affect at high RPM.
Retarded timing is exactly the opposite, it tends to lag on take-off & is only really useful at high RPM

 

[itsid]

IIRC (which I probably don't) I think 1/16" gives you around 4°...

Advanced timing is good for bottom end power but, tends to lose the affect at high RPM.
Retarded timing is exactly the opposite, it tends to lag on take-off & is only really useful at high RPM

Not exactly
Every 0.006" you remove from the key is equal to 1 degree advance.

so 0.024 is a 4° advanced timing ... that'd be 3/128

And again.. advanced timing is good for higher revolutions, and bad on lower revolutions,
that's why timing will advance in cars as soon as the motor revs up remember?

'sid

 

[Donald E. Jones]

I am building an ARC box stock 6.5 BSP engine with header and silencer. I am adding a + .010 billet rod and possibly a flat top piston. I haven't decided on this yet. This engine has a .615 bored and jetted carb.


Don Jones

 

[firemanjim]

Ahhh..... well, then ask your parts supplier how much advance they recommend. They can give you the low down on it and whats best for the parts you have. They wont screw you around because you are "free advertising".....
And Sid is right about the timing advance. You can file off a few thousandths on a stock key to get a little advance for free... I read about it in the best go kart info source around....... (DIYGK)

 

[Donald E. Jones]

After doing some more research, I have concluded that 8 degrees of advance is about what I need for my particular setup.

Don Jones

 

[Donald E. Jones]

I just took a look at my ARC billet flywheel, and it already has 32 degrees of advance built into the key way. With these particular flywheels, no offset key is needed. So, be sure to check the amount of advance built into your flywheel before installing an offset key.

Don Jones

 

[itsid]

After doing some more research, I have concluded that 8 degrees of advance is about what I need for my particular setup.

Don Jones

strange.. EVERYONE thinks he NEEDS a 8° key...
I can't believe that...
yes.. it revs even higher, but you will losse on the bottom end.
I'd try 4° or maybe 6° first, otherwise you' might end up with a high revving engine that hasn't enough power to even get there
(well exaggerated..)

I just took a look at my ARC billet flywheel, and it already has 32 degrees of advance built into the key way. With these particular flywheels, no offset key is needed. So, be sure to check the amount of advance built into your flywheel before installing an offset key.

Don Jones

No it doesn't!
inbuilt is 8° advance; it's at 32° BTDC
So yeah.. not much choice if you don't pay extra for the adjustable version (25°-39° BTDC)
Or get a timing key and install it the other way around

'sid

 

[Donald E. Jones]

'sid,
If I understand correctly, you are suggesting using offset keys in reverse to retard timing? Good idea, I like it !

Don Jones

 

[mckutzy]

Well this doesnt answer my question above, but it add to the understanding of the whole debate.
http://www.foxvalleykart.com/timing2.html

Any more insight as to my question. Didnt know how to get google to help. Instead got this topic as a result????

 

[itsid]

missed that

In the same respect, with what typical mods does one advance/retard timing? And what gains/fails for such?

With what? you mean like what mod calls for advancing the timing?
None!, well no typical mod that is..
But it starts to make sense as soon as you want to increase the rpm even more.
(stiffer valve springs, billet rod & flywheel etc.)
then you're basically set up to let the engine rev even higher...
the thing is, that will move the ignition timing for lower rpms out of the sweet spot and you loose torque in the low end.
So you need to counteract with a head mod (increased compression, porting etc.) and/or a new Camshaft with a longer valve timing, to get more gases in the cylinder.

But then again, all that could increase the power on all rpms, and you could again advance your timing and start over again.

you shouldn't ever advance timing with stock valve springs,
it just doesn't make any sense.

'sid