ZX6R Misfire.

evoboy · World Chat Champion Joined: 20 Aug 2009 Karma :

Been having a problem with a misfire on my J1 zx6.

Started after a ride where i parked the bike up and left it there for a few hours. Came back to have it only running on 3, so limped home and removed the rather rusty, old plugs and replaced. It now rides fine, so long as the headlights arent on?!

With the headlights on when the bike is first started from cold, itll idle fine for all of 5mins then starts to run a tad lumpy, which just gets worse as the engine gets hotter, to the point of it running on 3 ( with the odd sign of the 4th coming in very breifly). Once i start riding the bike and theres no load on the engine, it performs spot on, stick some load on the engine ( low revs) it splutters between 3 and 4 cylinders till the revs get up a bit.

It idles and rides fine with the headlights off.
It rides fine at anything over 4k revs, even with the headlights on.
It fires up first time from cold, even after standing for a few days.

Cheers.
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Suzuki GT250 x7------- Fazer 600------CB250RS------Aprilia Rally 70----- Bandit 600

APT Motorcycles

temeluchus · World Chat Champion Joined: 01 Oct 2008 Karma :

I think that would point to a problem with your alternator or maybe battery. You load it up with the headlamp, which does draw a fair whack of current and it misfires as the ignition isnt getting enough juice.

Have you got a multimeter? be worth checking the voltages at the battery with the bike running, with lights off and on.
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Some shite cruiser. Now with guns and FREEDOM!

evoboy · World Chat Champion Joined: 20 Aug 2009 Karma :

Checked the batt with a multimeter. All seems good (voltage doesnt barely drop a volt with the lights on).

It now seems to be suffering from the misfire all the time now, lights on or not!

Guess i should start checking for a duff new plug, but whats the best way of doing this on a bike without HT leads or plug caps? I thought about just disconnecting a coil/plug cap thing one at a time, to see when it just constantly runs on 3 cyl?
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Suzuki GT250 x7------- Fazer 600------CB250RS------Aprilia Rally 70----- Bandit 600

APT Motorcycles

temeluchus · World Chat Champion Joined: 01 Oct 2008 Karma :

get it idling, and rev it up, peak output on the alternator should hit over 14v.

It could be a knackered relay or a corroded earth somewhere?

Its just that one of the first signs of power and battery issues is a misfire as electronic ignition doesnt like low voltages.
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Some shite cruiser. Now with guns and FREEDOM!