NGK Iridium causing missfire under load?

Hi all, over the weekend I did the valve clearances and changed the plug on my FX650e (in supermoto trim with full Doma system). I thought I would treat her to an Iridium plug as I have used these before on my 2 stroke bikes with great success.
Took her for a blast and I get a missfire when on full throttle high up the rev range, doesn't happen every time but really noticible when it occurs. I set the gap to 0.6mm as it says in the owners manual and did the valve clearances 1/6th of a turn as suggested on other threads, I took time over this to make sure I got it right, found the feeler guage method immpossible.
It's been raining in sunny England since so have not had a chance to ride since but I am going to put the old standard plug back in and see if the missfire dissapears.
Has anyone else had issues with the Iridium plug ?

Freaky said:

Hi all, over the weekend I did the valve clearances and changed the plug on my FX650e (in supermoto trim with full Doma system). I thought I would treat her to an Iridium plug as I have used these before on my 2 stroke bikes with great success.
Took her for a blast and I get a missfire when on full throttle high up the rev range, doesn't happen every time but really noticible when it occurs. I set the gap to 0.6mm as it says in the owners manual and did the valve clearances 1/6th of a turn as suggested on other threads, I took time over this to make sure I got it right, found the feeler guage method immpossible.
It's been raining in sunny England since so have not had a chance to ride since but I am going to put the old standard plug back in and see if the missfire dissapears.
Has anyone else had issues with the Iridium plug ?

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Make sure your plug cap and plug wire are in good shape when you put the old plug back in. My guess is that the Iridium plug is not the issue, but putting the old one back in will tell you quickly.

RE: Re: NGK Iridium causing missfire under load?

there ius a chance you have a dodgy plug for sure but i think 24 thou is too small a gap? i would have thought 28 to 32 was about right?

regards

Taffy

Thanks John, still raining here so can't really try bike in any anger but popped to shed and checked cap and lead and they are both in good order, clean with tight connections.

Taffy, 2003 owners manual states 0.6mm for the plug gap, I take it your suggesting widening the gap? What do you prehistoric measuements convert to in modern day mm? lol.

Also one thing I forgot to mention, the old plug always had a good reading, light brown colour, the Iridium plug is showing up pale as though it's running lean?

Thanks

whats the code on that plug?

4 thou to .1mm so i was suggesting that .7 or .8 was more like it. i don't think we've discussed it much here but.6mm is what we had with the old points ignitions etc and when everything went to electronic ignition out went the gaps to 28-32 thou. i regap all my plugs to 28 thou (0.7mm).

regards

Taffy

Taffy, plug code is DCR8EIX. I have always had great results on my 2 strokes with a noticable improvement in performance, ease of starting and lack of fouling. I will increase the gap to 0.7mm and give it a go before I put the old one back in.

On a different note, whilst the tank was off I noticed a black breather type pipe coming from the carb, it comes out of the right hand side and goes upwards over the top of the carb, it is open at the end. Is this how it should be? I can't see anywhere it could plug into but it isn't long enough to go together with the other breathers which exit below the carb.
Any ideas anyone?

you should have two or three breather pipes out the carb and they should all point downwards. so get the zip ties out!

regards

Taffy

Freaky said:

Taffy, plug code is DCR8EIX. I have always had great results on my 2 strokes with a noticable improvement in performance, ease of starting and lack of fouling. I will increase the gap to 0.7mm and give it a go before I put the old one back in.

On a different note, whilst the tank was off I noticed a black breather type pipe coming from the carb, it comes out of the right hand side and goes upwards over the top of the carb, it is open at the end. Is this how it should be? I can't see anywhere it could plug into but it isn't long enough to go together with the other breathers which exit below the carb.
Any ideas anyone?

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Hi Freaky,

Just so were all on the same page, your plug is a DCPR8EIX. I use them as well.

Since your bike is an 03, that means you have a dellorto carb, there should be two vents, and one over flow tube on that carb. I know what you mean about the vent tube going up and over the top of the carb, and it comes back down again and is dangling at the back of the motor right? There should be another on the left side of the carb that does the same thing, right? Then there should be another tube located lower and towards the back of the carb that just goes down towards the back of the motor. Right? None of these tubes should be pinched or kinked in anyway and the ends should be clear of debris.

The two tubes that go up and over the carb are float bowl vents, without them, the fuel would not flow from the float bowl up through the jets in the venturi of carb which is a low pressure area. Without the vents the fuel would be vacuum locked. That's why a bike that is ridden in deep water, but not over the air filter will quit, because the water is blocking the air from flowing into the float bowl.

The other tube is a float bowl over flow tube, and this one spills fuel out of the now too full float bowl when the bike tips over too far and keeps the bike from flooding, or at least that's the idea.

Are we to assume that from reading your post that: A- you just got this bike? B-The bike was running fine until you adjusted the valves and put in the iridium plug? C-You are not having any trouble starting the bike?

I had a similar problem with my 01 501, but it was the stator that was starting to go bad. It would start and run fine until it got thoroughly warmed up. The when you started to open it up and the pressure rose in the cylinder and this pressure rise would snuff out the spark. It drove me nuts because it wouldn't do it every time I opened the throttle when it was warm, and if you dipped the clutch and blipped the throttle it would rev right up. I went over everything on that bike at least 2 or 3 times, electrical, carb, wiring.

I spoke with Sparks and he put me straight as to what the problem was, I put on another stator that I had and the problem was gone. I then sent that stator over to him and had him rewind it for far less than the cost of new.

So, put the old plug back in and if it does it again then you know it's not the new plug.

As far as your valve adjusting goes. The method you described is fine. They do make some small Z shaped feeler gauges of .1mm(.004") and .13mm (.005") thicknesses that are very easy to use. I would secure one of these and just double check your valve lash with one of these. I believe on your year bike the valve lash was spec'd to .1mm. With the 1/6 turn method, the feel should be quite snug. I tried using the 1/6 turn method and this is what I experienced when referencing the 1/6 method to the feeler gauges.

Thanks for the detailed reply DaleEO, very informative. That sorts out the carb venting, all pipes are unblocked etc, cheers.
Have had the bike for about a month now, ridden it for 14 hours so far, completed two oil and one filter change. Bike has been running as sweet as a nut until after the recent work. Starting is all sorted now, had the usual problems of perfecting my tecnique (39 years young and this is my 1st four stroke out of 19 bikes over the years) but can start it after 1 to 4 kicks now.
Have been reading various posts this afternoon and seen some simular probs due to stator as you have kindly pointed out.
Hopefully just the plug, will let you know how I get on as soon as the clouds dissapear over UK.

Thanks for your help, much appreciated.

freaky

i swear by the denso IXU24 plug so if your missfire continues please consider this way forwards.

regards

Taffy

Just thought I would keep you updated with regard to the missfire. Put the original plug back in and took it for a spin, all good, no missfire and pulling strong again until I changed from low to high on the switch on the right side of the bars, been told this alters the ignition curve but I never seemed notice any difference. Runs great on LOW so not concerned too much but could this point to something on it's way out like stator as dale suggested?
Thanks Trevor

go to the ignition section of the doc. there you'll see an article on the ignition timing marks being in the wrong place!

this could be worth persueing.

regards

Taffy

FYI,

The high low switch only alters the ignition below 6000 rpm. Above 6000 rpm the curve is the same. If you unplug the hi/lo switch it reverts to the hi curve. On the replacement CDI's that you get now a days, the gray wire for the low curve that goes to the hi/lo switch is no longer there.

Before I replaced my CDI on my 01 501, I used to run it in the low curve for most conditions. I would go to the high curve in the deep sand. The low curve made it a bit easier to ride in the loose rocks.

As Taffy mentioned, have a look at the doc in regards to the timing marks.