PE VERSUS RM TIMING CURVES AND CDI BOXES??

[vettepilot]

Does anyone know how the PE and RM timing curves compare?

I found a source for PE replacement CDI boxes, and wonder how they could be used on RM's.  Possibly by advancing or retarding the base timing a bit?  This is also relative to the fact that at some point I will be putting an RM cylinder, head, and pipe on my PE, and I'm curious about the ignition curves.

Thanks!
Vettepilot 

[Admin]

You can find more info in Luke's Pure Enduro One Drive folders about CDI's, Stators, PE degree wheel etc.
You shouldn't, I think, worry about the curves as it's a CDI ignition and primarily controlled by the rpm, you just need the correct stator plate/ stator combination set at the correct position as seen and explained in your owner manual.
Perhaps oversimplified, but I would start with the base adjustment for the ignition and everything should fall in place.
If you change the cylinder head, cylinder, airbox or pipe, those will need to be done through jetting, not the ignition IMO.
I have an RM cylinder on my 250B PE because my friend had one available and the cylinder on the bike when I purchased was seized and he was kind enough to give it to me. it just worked, some fine tuning on the carb but you can always be fine tuning endlessly.....
This info and more can be found on the forum, look at "Other PE Sites which will also have a listing for Luke's RM Info.

And others can add their experience.

[vettepilot]

Hi,

Thank you for the info and links, but I couldn't disagree more with your comments as I understand them.

The static timing is determined by stator position, but overall timing, advance, etc., is controlled by the CDI, referenced by rpm.

For example, from what I've been able to discern, the PE timing is 19.5 degrees BTDC at 8000 rpms, while the RM is 6 degrees BTDC at 8000 rpms.

Most two stroke timing maps start at 5 to 10 degrees BTDC at 1500 rpms, then rise very quickly to 18 to 25 degrees, then at higher rpms begin to reduce the advance to around 5 to 10 degrees at max power. This varies a great deal depending on the bike and it's intended use, power output, pipe, etc., but it is all literally accomplished by the electronics in the CDI. It is also very, very different than what would be the best timing curve for a four stroke engine.

An engine can run with the wrong CDI box, but the timing will not be optimum.

Note that when you set the timing by positioning the stator, you are setting the maximum advance that can be achieved. From there, the CDI itself will adjust the timing, based on rpms, to whatever the engineers decided was best.

Thanks,
Vettepilot

[Admin]

Ok your points are well made, I'm not prepared for that level of discussion.
I would hope anyone on the forum who may have done more can supply your answer. Some did some readings I think with oscilloscopes and such in the past but I don't know if the info is in the archives here. 
There should be some links or information on alternate ignitions and you might find more pertinent information from those companies.
You might find some information on Fabrices site as he is very technical if you look there.
There is a lot of information to research here or in the links.