Ignition advance

Small question. When the mechanical advance advances the spark at 2,500-3000, should it do so "smoothly", from no adv to full adv OR does it happen in one quick hit? I would have thought it would happen smoothly but mine does seem to go all at once?

try lubing things up a little bit;)

The ones on my GS1000 and KZ1000 go pretty much all at once. More a switch than a valve.

-Duck

Wireman. I see you answered at the same time. Both GS and KZ advance have been disassembled, cleaned, lubed, and they still go from no advance to full over such a small RPM range that it may as well be all at once. Is this not the way they are supposed to behave? GS pulls smoothly in all gears.

Post edited by: Duck, at: 2006/04/07 17:00

Barney-

Back when the GS was sticking, I could watch it with the timing light and it would jump between full retard and full advance. Took it apart, cleaned with scotchbrite, don't want bits of steel woll around the magnets) and lubed. Now it behaves as per my initial reply. After hearing from wireman I'm not sure that's right

Post edited by: Duck, at: 2006/04/07 17:04

as long as they are moving freely id say youre right.on automotive applications and distibutors we use in the boats you adjust how fast the advance comes in by changing the springs and weights in distributor.my dad bought me a new dyna 2000 but its still at his place ill call and ask him if it comes with differant springs.

Old, tired, springs maybe?

The advance (on mechanical advancers) is operated by centrifical force, as the rpm increase, the force applied to the springs by the weights increases. The springs require X force to extend 1 mm, then X+X force to extend another 1 mm, then X+X+X force to extend another 1 mm, so the advance increases with rpm.

I have not checked, but my guess is that the advance starts increasing ~2k rpm, amd should be at full advance around 3.5k rpm, if the advance starts much earlier there will likely be a problem with detonation.

I'd type more but there is supposed to be a tornado headed this way, and the hail just started, got to go watch for it.

Nothing this time

Back in the day, a spring kit and access to a distributor machine was required for every serious tuner

Ain't progress wonderful, now it's ignition controllers with fully programmable advance depending on rpm, engine load, and rate of rpm increase

Post edited by: steell, at: 2006/04/07 18:14

according to dear ol dad around 1500 is where it starts and should be in around 3500.check at idle then give it some fuel and see where it starts to advance,make sure everything is lubed and not sticking.

Starting point for the advance seems to vary among different motors, but max advance always seems to be 35-38 degrees BTDC, and usually ~3500-4000 rpm. I think the maximum advance is determined by flame travel, since it seems to be the same for all motors running the same type fuel, I think alcohol runs around 45 degrees advance (not sure enough to bet any money on it though)

steell wrote:

Starting point for the advance seems to vary among different motors, but max advance always seems to be 35-38 degrees BTDC, and usually ~3500-4000 rpm. I think the maximum advance is determined by flame travel, since it seems to be the same for all motors running the same type fuel, I think alcohol runs around 45 degrees advance (not sure enough to bet any money on it though)

The ideal ignition is timed to give the maximum pressure at the optimum crank angle. Pressure build rate depends on fuel, compression and mix. Best angle depends on RPM and load.

The narrow range mechanical advance is not ideal but works very well. Adding vacuum input would make it better. Full computer control can be close to ideal. It's not a whole lot of improvement for the $ but IMO worth going to computerized management if you want to get the most from the engine.

-Duck

On the 550, it is a smooth transition.

Post edited by: loudhvx, at: 2006/04/10 02:46