When does it spark

surfdude · May 18, 2008

Hi all,

I'm a bit confused about the ignition time on my FE550 04. When i look at the explanation of a 4 stroke engine on Wikipedia http://en.wikipedia.org/wiki/4_stroke, i see that out of 4 strokes only 1 ignition takes place on the power stroke.

When i turn my flywheel 360 degrees, it does 2 out of the 4 strokes, does this mean that my Husa sparks twice on 4 strokes? If not, is there an other way to find out on which of the (upper) strokes it sparks?

Perhaps it is a silly question, but i rebuild the engine, and alligned all the dots correctly, but just ain't sure about the ignition.

whosahberg · May 18, 2008

it fires on one stroke of 4 , the ignition system has sensors to detect the correct stroke .

surfdude · May 18, 2008

That's what i was afraid for, so how can i find this stroke?

whosahberg · May 18, 2008

have a think about the 4 stroke cycle ... intake , compression , power stroke , exhaust . also the link you gave gives the info you require .

surfdude · May 18, 2008

Not sure what you mean exactly, but i need a way (if one exist) to find the powerstroke with the camchain on, but not linked. So i can't do it by trial and error just yet. Or do i need to take my 50% change and give it a go?

Chas · May 18, 2008

whosahberg said:
it fires on one stroke of 4, the ignition system has sensors to detect the correct stroke .

If true, this would be very unusual as most four stroke engines fire once every 360 degrees with a 'wasted' spark every other time.

whosahberg · May 18, 2008

i stand by my answer ... sorry

Taffy · May 18, 2008

beat me to it chas.

as i'm aware if you put the ignition pick up on the crank you get a very accurate soark but you also get a wasted spark. it doesn't hurt for the engine to have a spark when the gases are burnt up and being pushed out past the exhaust valve.

the ignition surfdude is on about will have been slowed to half crank speed by being fitted on the camshaft or as in old fashioned cars a shaft that came out the side of the block that as i say had been slowed to half engine speed.

regards

Taffy

awilksch · May 18, 2008

if it sparks every revolution then there will be a spark at the top of the compression (up) and power (down) stroke as well as between the exhaust (up and before the intake valves open in the induction (down) stroke.

Im in the school of thought that the coil only fires every second revolution (??) otherwise there would potentially)be risk of damage to the piston / barrell from a secondary detonation of residual unburned fuel??

Confused... wheres sparks, he would know for sure.

Azza.

sparks · May 18, 2008

awilksch said:
if it sparks every revolution then there will be a spark at the top of the compression (up) and power (down) stroke as well as between the exhaust (up and before the intake valves open in the induction (down) stroke.

Im in the school of thought that the coil only fires every second revolution (??) otherwise there would potentially)be risk of damage to the piston / barrell from a secondary detonation of residual unburned fuel??

Confused... wheres sparks, he would know for sure.

Azza.

If you have a flywheel ignition, depending on how it is triggered you will either get a spark every 360 or a spark every 180 degrees.
If the spark is triggered by a pulse coil as is the Kokusan and the SEM you will get a spark every 360, if the trigger coil is also the source coil doing two jobs then you will get a spark every 180 this is because you are using either two norths or two Souths to trigger the spark from the magnets in the flywheel.
There is no chance of causing damage to the piston because on th exhaust stoke you are just pushing gas out some still burning hence if the ignition timing is to far out his could cause valve burning as the temp of the out going gas is very hot.
Damage can be caused to the piston on the ignition stroke called detonation, this where the fuel is burnt unevenly in numerous small explosions and will usually lead to the perimeter of the piston being eaten away, holed pistons this is usually caused by mal adjusted ignition timing.

We've all run a four stroke engine with no headers attached and what do you see yellow or blue flames coming from the exhaust port, yellow is a cool flame and blue is hot.

Regards

Steve.

whosahberg · May 18, 2008

my answer is as per the otto cycle [ refer the link above ] my answer is deep within the context of the question .

surfdude · May 18, 2008

Gave it a try, and found out that there is a spark when the lobes are at 11 and 1, but also when the lobes are at 7 and 5. So there seems to be a "wasted" spark. On the flywheel there is a lump, which passes the pulse coil every 360 degrees (2 strokes), which triggers the spark i guess. Anyway, it looked good, but i still have to start the engine, once completely rebuild.

Thanks for your help.

When does it spark

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