Colortune plug drama

[dom14]

Hey Guys,

I'm having trouble using Gunson Colortune spark plug with my RB30 head.
Basically the central electrode sparks onto the body of the head inside the hole instead of sparking inside the combustion chamber.
Wrapping central electrode with piece of rubber tube and inserting a rubber sleeve inside the spark plug hole wasn't able to stop the spark either.

What should I do to get this Colortune thing to work with the RB30 head?

I can see the deep hole on the spark plug hole is the reason for easy spark leak, but Gunson should have come with a ceramic coating around the electrode to prevent that, just like normal spark plugs.

Please have a look at the pictures to get a picture of what I'm saying.

Any ideas to get the thing to work, will be appreciated.

P.S. The Gunson spark plug gap appears to be around 1mm or so. Not too far from stock 0.8mm requirement for RB30 spark plugs. I don't think I can adjust the Gunson plug gap without damaging it. Gunson plug is obviously way shorter and and the spark ignites good 1-2cm away from the location where it happens with a stock spark plug. I'm not sure whether that helps, but I'm guessing it's requirement to be able to see the combustion colours clearly through the sight glass ring of the Gunson plug.

BTW, my RB30 is dual fuel and I used the colortune plug on LPG.

[dom14]

I wonder why the spark happens from more resistant & longer path outside the spark plug when it can happen from the least resistant & shortest path inside the spark plug from the tip of the electrode!!!??

[dom14]

Any thoughts folks? No?! :)

[NissanGQ4.2]

I know nothing about them, but did read this on the net

"Spark plug reach is the distance between the end of the spark plug threads and the seat or sealing surface of the plug. Plug reach determines how far the plug reaches through the cylinder head. If spark plug reach is too long, the spark plug will protrude too far into the combustion chamber and the piston at TDC may strike the electrode. However, if the reach is too short, the plug electrode may not extend far enough into the cylinder head and combustion efficiency will be reduced. A spark plug must reach into the combustion chamber far enough so that the spark gap will be properly positioned in the combustion chamber without interfering with the turbulence of the air-fuel mixture or reducing combustion action."

I would take a guess the plug is 2 short 2 be doing anything useful............. but I'm know mechanic and not at all mechanically inclined

[dom14]

I know nothing about them, but did read this on the net

"Spark plug reach is the distance between the end of the spark plug threads and the seat or sealing surface of the plug. Plug reach determines how far the plug reaches through the cylinder head. If spark plug reach is too long, the spark plug will protrude too far into the combustion chamber and the piston at TDC may strike the electrode. However, if the reach is too short, the plug electrode may not extend far enough into the cylinder head and combustion efficiency will be reduced. A spark plug must reach into the combustion chamber far enough so that the spark gap will be properly positioned in the combustion chamber without interfering with the turbulence of the air-fuel mixture or reducing combustion action."

I would take a guess the plug is 2 short 2 be doing anything useful............. but I'm know mechanic and not at all mechanically inclined

Yeah, the colortune plug I bought is ok for motorbikes, but perhaps not so for RB30.
It still doesn't explain the spark mayhem though.

Why does the spark happens outside the plug, instead inside at the tip of the electrode where it suppose to happen?

Something's wrong with the colortune plug or the way I do it.

[dom14]

These are the video of "spark leak". It appears it only sort of happens when the engine's on idling.
It also appears it does it more on petrol than on LPG.
First one is petrol and second one is LPG.

https://www.youtube.com/watch?v=ODnfyXwK9Wc&feature=youtu.be

https://www.youtube.com/watch?v=F-_9GMs8JPc&feature=youtu.be

[dom14]

This is video with silicon sort of rubber ring around the place where I think the spark leak happens & with a high impedance ignition lead. First one is the normal ignition lead. Second one is the high impedance ignition lead. Both videos have the silicon rubber insulation ring around the gunson plug extension where the spark leak happens.

https://www.youtube.com/watch?v=FNtiF9ONp5Q&feature=youtu.be

https://www.youtube.com/watch?v=-tKOTXTkaJU&feature=youtu.be

Does the combustion colour look ok, in terms of rich/lean mixture?!!
I'm also revving/pumping the accelerator to see what colour the combustion produces.
It appears to be burning lean during accelerator pumping!

As you can see the spark leak happens regardless of low or high impedance ignition lead.

[Cuppa]

I reckon you’re largely talking to yourself on this. I may be wrong but suspect that most here have never seen a Gunsons Colourtune. I’ve still got one in a drawer out in the shed, would’ve bought it around 35 years ago (in the UK) & used it to tune Triumph twins. Never had the spark leaking issue, but always found use to be a bit of a fiddly process. Can you buy them today in Oz?

[dom14]

I reckon you’re largely talking to yourself on this. I may be wrong but suspect that most here have never seen a Gunsons Colourtune. I’ve still got one in a drawer out in the shed, would’ve bought it around 35 years ago (in the UK) & used it to tune Triumph twins. Never had the spark leaking issue, but always found use to be a bit of a fiddly process. Can you buy them today in Oz?

Yeah, you can. It's around $100 or so locally. I thought that's bit too dear for a spark plug with a sight glass built into it.
So, I orderd it from UK for $50.
I actually ordered it for the little bike, but was told it's good for tuning any engine.
Cross sparking kinda baffles me a little bit.
I have to find the real reason behind it, hence the reason I keep posting what I do here. :)

[NissanGQ4.2]

I actually ordered it for the little bike, but was told it's good for tuning any engine.
Cross sparking kinda baffles me a little bit.


Does it work in the bike without sparking?

[dom14]

Does it work in the bike without sparking?

My bad, i actually haven't tested it in my bike yet. I'll do it tomorrow.

BTW, I just had an unexpected surprise.
I just swapped the carby back to the original carby.
Original carby has a problem of running too rich which i haven't figured out how to fix yet,
so it's still running too rich and Gunson plug confirmed it.
Surprise it that with the original carby(and it's running rich),
the spark doesn't cross spark at all. No spark leaks at all.
I wonder whether it has something to do with the carby running rich(rich combustion).
I can't explain this yet.
Any ideas?!!!!

P.S. I used the copper washer(sleeve) that goes with the Gunson plug this time.
I think that might be the reason.
May be I'm suppose to use the copper washer all the time.
I'll have to do it again later tonight to find out.

[NissanGQ4.2]

Original carby has a problem of running too rich which i haven't figured out how to fix yet,
so it's still running too rich and Gunson plug confirmed it.
Surprise it that with the original carby(and it's running rich),
the spark doesn't cross spark at all. No spark leaks at all.
I wonder whether it has something to do with the carby running rich(rich combustion).
I can't explain this yet.


Funny you should say that because I watched the video then read a Colortune post about the colors and thought it was running rich in the vid you posted and wondered it it was because it was running rich and was going 2 ask u but thought surely it wouldn't matter....

But as I said I'm far from mechanical minded

[dom14]

Funny you should say that because I watched the video then read a Colortune post about the colors and thought it was running rich in the vid you posted and wondered it it was because it was running rich and was going 2 ask u but thought surely it wouldn't matter....

But as I said I'm far from mechanical minded

I think the copper washer might have something to do with that.
I don't think two different carbies are the cause of the spark leak issue.

I'll retest first thing tomorrow morning and find out.
Cheers

P.S.
Come to think of it, rich mixture may be facilitating the spark inside the combustion chamber,
as oppose to the spark leak outside.

[dom14]

Funny you should say that because I watched the video then read a Colortune post about the colors and thought it was running rich in the vid you posted and wondered it it was because it was running rich and was going 2 ask u but thought surely it wouldn't matter....

But as I said I'm far from mechanical minded

BTW, why did you think it's running rich in the video?
I thought, the flame was blue, for the most part.
It did momentarily turn yellowish when I pumped the accelerator,
But, I reckon mixture was ok for the most part with the spare carby.
It's totally different story with the original carby though.

[dom14]

Funny you should say that because I watched the video then read a Colortune post about the colors and thought it was running rich in the vid you posted and wondered it it was because it was running rich and was going 2 ask u but thought surely it wouldn't matter....

But as I said I'm far from mechanical minded

Sounds like you're right about that.
The rich running carby apparently have some effect on spark leak issue.
No spark leaks with the rich running spare carby, and the copper washer has no effect on that.

https://www.youtube.com/watch?v=2MImI1DVbJg&feature=youtu.be

https://www.youtube.com/watch?v=sHma_C53OE4&feature=youtu.be

Increasing the rpm does get the flame to blue colour, indicating proper combustion at higher revs.