NC30 misfiring when hot

[krisztian_andre]

It's misfiring with the engine behaving like when it's runnig out of petrol when warmed up. Also my fuel consumption is way up.

[CRM]

Assuming you have changed your plugs, next thing would be a coil breaking down when hot.

[krisztian_andre]

I'm soaking the plugs in contact cleaner and will burn the deposits off in a gas flame. Bought coils and CDI from ibby, we'll see if it helps...

[tigerclaw]

Just for good measure have a look at your sparkplug leads to see they arent old , crossfiring or shorting on something... and als make sure your plug gaps are correct

[royster81]

My friends rvf is doing the same. So far the carbs have been cleaned, coil changed, ht changed, plugs changed, carbs balanced, and a new battery fitted. It idle it miss fires but over 3K it rides normal and pulls like a train.

The last thing I can think of is reg/rec but we are at a loss atm

[pip]

Test the plug caps.

Phil

[Cammo]

at idle it miss fires but over 3K it rides normal and pulls like a train.

The last thing I can think of is reg/rec but we are at a loss atm

Sounds to me like a blocked carb idle circuit Rhory, common problem when bike's go for periods of no use. It might take a few sessions in an ultrasonic bath to clear it out.

If you have an infrared thermometer you might be able to find which carb is responsible by measuring the downpipe temperatures which will save you time. That's what I'd be doing.

Also worth checking HT lead resistance and charging system voltage first as these tests are a lot quicker to perform.

[royster81]

It's easy to figure out which cylinder isn't firing as the pipe takes so long to warm where the others where piping hot within minutes. It's the rear right where the vacuum pipe comes off.

He's check plug cap resistances and charging system voltage but at the battery at idle it was a little high at just over 14.1v. He's going to remove and clean the idle circuit again so finger crossed.

[tigerclaw]

Random idea - but try and run it with the airbox off and spray a little fuel into the cylinder (plastic spray bottle or similar), see if the cylinder comes alive ... that should help decide if it is a petrol or electrics issue

[krisztian_andre]

Random idea - but try and run it with the airbox off and spray a little fuel into the cylinder (plastic spray bottle or similar), see if the cylinder comes alive ... that should help decide if it is a petrol or electrics issue

That's a good idea. The misfire got better, it only happens now under high load around 12000rpm high gear and only for a split second and sporadically.