Re: Advance timing and revs vs power
Posted: Sun Mar 02, 2014 5:38 pm
It sounds as though your ignition curve or initial setting is wrong for your motor. Adding a variable ignition system (subject to getting the right one and setting it up correctly) should add lots of power lower down the rev range, have just as much power in the mid revs, then lose no (or very little) power at max revs and run a lot cooler.
What you are suffering is that your ignition has retarded too far too soon. If your bike was making good power before at 18 dbtdc (for example) at 6500 RPM then that's what your bike should still be running at @ 6500 RPM. However, it sounds s tough your bike has retarded too far and is probably running at something like 12 dbtdc @ 6500, struggling to burn the mix off and struggling to make any power.
To get over this issue you could a) turn the stator anti-clockwise so that it was then firing at 18 dbtdc @ 6500.... or b) you leave the stator where it is and pick an ignition curve that does not retard so quickly and will still be at 18 @ 6500, rather than 12. Sadly, you can't just guess which is the right course of action as you might well then find you are too advanced at 2500 RPM or 9000 RPM, depending on they way you go about it. This shouldn't be a case of guesswork, you should be determining what is right for you by seeing where it fires at what RPM and then seeing if that is appropriate for your tuning and setup (particularly your exhaust).
I have the benefit of a rev counter on my scoot so I can see what the firing point is (using a strobe and mag housing marked for a range of about 26 to 12 dbtdc) and at what revs. Only by using the combination of rev counter and strobe could I get some idea of how the auto advance/return function actually plays out. I did note that swapping between an Agusto 8000 unit and 6000 unit resulted in a massive difference of initial low rev position, with me needing to extend the slot massively in the stator base to allow me to get the starting, mid and final firing points that I needed, with the rev counter telling me where these revs were.
Many people try fitting an auto advance/retard kit without even having a strobe, let alone a rev counter! In these cases it is either good luck or good dealer advice that allows it to work... if it does! What is very common is to fit one of these at home, without the kit to set it accurately, then find that it loses power or gets too hot and causes problems
If you don't have the tools and knowledge to make one of these work then it is far better to stick with tried and tested static ignition.
It should also be pointed out that the change to auto advance/retard will normally require a rejet of the carb to suit the new hotter spots (low down) and cooler spots (higher up), hence why many people want a decent tuner/dyno centre to set these gadgets up for them, where ignition performance and jetting can be looked at at the same time.
I do have pals that have fitted these multi curve units and simply flicked through options until they found something that worked but that was more luck than judgment!
Good luck with it.
Adam
What you are suffering is that your ignition has retarded too far too soon. If your bike was making good power before at 18 dbtdc (for example) at 6500 RPM then that's what your bike should still be running at @ 6500 RPM. However, it sounds s tough your bike has retarded too far and is probably running at something like 12 dbtdc @ 6500, struggling to burn the mix off and struggling to make any power.
To get over this issue you could a) turn the stator anti-clockwise so that it was then firing at 18 dbtdc @ 6500.... or b) you leave the stator where it is and pick an ignition curve that does not retard so quickly and will still be at 18 @ 6500, rather than 12. Sadly, you can't just guess which is the right course of action as you might well then find you are too advanced at 2500 RPM or 9000 RPM, depending on they way you go about it. This shouldn't be a case of guesswork, you should be determining what is right for you by seeing where it fires at what RPM and then seeing if that is appropriate for your tuning and setup (particularly your exhaust).
I have the benefit of a rev counter on my scoot so I can see what the firing point is (using a strobe and mag housing marked for a range of about 26 to 12 dbtdc) and at what revs. Only by using the combination of rev counter and strobe could I get some idea of how the auto advance/return function actually plays out. I did note that swapping between an Agusto 8000 unit and 6000 unit resulted in a massive difference of initial low rev position, with me needing to extend the slot massively in the stator base to allow me to get the starting, mid and final firing points that I needed, with the rev counter telling me where these revs were.
Many people try fitting an auto advance/retard kit without even having a strobe, let alone a rev counter! In these cases it is either good luck or good dealer advice that allows it to work... if it does! What is very common is to fit one of these at home, without the kit to set it accurately, then find that it loses power or gets too hot and causes problems
If you don't have the tools and knowledge to make one of these work then it is far better to stick with tried and tested static ignition.It should also be pointed out that the change to auto advance/retard will normally require a rejet of the carb to suit the new hotter spots (low down) and cooler spots (higher up), hence why many people want a decent tuner/dyno centre to set these gadgets up for them, where ignition performance and jetting can be looked at at the same time.
I do have pals that have fitted these multi curve units and simply flicked through options until they found something that worked but that was more luck than judgment!
Good luck with it.
Adam