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Make your own 'colortune' plug...

  • Thread starter Thread starter tfb
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T

tfb

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G'day all,

The 'Gunson Colortune' plug is an amazingly effective and easy bit of kit to use, for tuning the idle (pilot) mixture on your VM carburettors.

Here's how I made my own 'colortune' plug -- and if you're feeling up the task, you can make your own too:

http://www.theflyingbanana.com/tfbtechtips.htm

Cheers,
Mike.
 
subscribed. Thanks. I really like my colourtune but it's all made of plastic, it's only downside.
 
I will make one and see how it is. I have always thought that having 4 installed would be much easier than doing one cylinder, removing the colortune and going thru all that process 4 times on a hot engine.

I love mine but the 4 installed theory seems much more attractive and less time consuming at that.
 
Got the porcelan out. Think I am gonna go with a stainless steel center electrode and just rebend the outer one over like it was before. Need to get some clear epoxy and then assemble one.
 
Well got one made. Setting all night to be sure epoxy is real hard. Seems the epoxy is extremely thick as compared to the real colortunes area. Guess I will see soon enough of its clear enough to actually be of use.
 
Guess I will see soon enough of its clear enough to actually be of use.
Click to expand...
The epoxy I used is somewhat opaque, but when I'm using the plug it's easily clear enough to see the combustion flame colour.
 
I used clear epoxy. The overall thickness is what my concern not the clarity of the media.
 
Its better to only use 2 colortunes at a time as they get hot and I have had 3 leads melt off the threaded end. had to weld them back together to get around that. its like they are pressed or the heat shrink on the lead is all that holds the lead to the threaded end that threads to the top of the colortune.
 
Well it works as advertised. I am gonna redo it though and see if I can get then epoxy a tad bit clearer. I think I got something in it when I poured it down the plug by not having the inner plug surfaces perfectly clean. Will report back after number 2 has sat all night to fully cure the epoxy.
 
All in all its a working plug but I think Colortune has the absolute edge as far as clarity and seeing the color nice..was a cool little thing to do though. I will just rebuy another colortune should this one go bad.
 
azr said:
subscribed. Thanks. I really like my colourtune but it's all made of plastic, it's only downside.
Click to expand...

any idea what kind of plastic they use in the middle? or could be used?
I work in a plastic factory..... :-\\\:-\\\:-\\\
we have some teflon that melts at 625 F, but I wouldn't want to be involved if it melts inside a motor.

and why is the center electrode recessed? did I miss something? I would have made it flush with the end of the plug.
 
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All in all its a working plug but I think Colortune has the absolute edge as far as clarity and seeing the color nice
Click to expand...
Yes, they've got a nice product, that's for sure. But after a bit of fiddling with depth of the electrode within the plug, I got a very clear combustion flame colour visible through the epoxy. Which brings me to exdirtbiker's question...

and why is the center electrode recessed? did I miss something? I would have made it flush with the end of the plug.
Click to expand...
The centre electrode in the original Gunson 'Colortune' is very recessed... and at first I thought I would make my tuning plug with a 'normal' electrode flush with the end of the plug, as you suggest.

BUT the thing was that while the cylinder was firing along nicely, there was hardly any combustion flame colour visible. :-k

So I recessed the electrode to be more like the Gunson item, and suddenly I got a much more visible combustion flame. ;)

So I think having the electrode sufficiently recessed makes a BIG difference as to how visible the combustion flame is.
 
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AHHH!! What I did was make the electrode go all the way down like the regular spark plug and rebent the outer one over and set the gap. Maybe I will rebend the center one and give it another go.
 
I wouldn't be too fussy about setting the gap... in fact, it seems a nice wide gap of 2-3mm or so seems to work just fine. Remember this is a plug for low speed (idle) mixture setting, so gap prob. isn't that critical. Main thing is to have a nice fat spark, so a nice wide gap seems to work just fine.
 
Actually ( on my VMs anyway ) once I dialed the pilots I run the RPMS up to around 4,000 and dialed the side mixture screws and watched as the color changed. Got all 4 nice and blue at that RPM also.

Thinking its as close as its ever gonna be at idle and mid range cruising RPMS.
 
Actually ( on my VMs anyway ) once I dialed the pilots I run the RPMS up to around 4,000 and dialed the side mixture screws and watched as the color changed. Got all 4 nice and blue at that RPM also.
Click to expand...
Chuck, you've got no idea how your words there led me to having a 'eureka' moment with tuning my GS1000 (but unlike Archimedes, I didn't then run off down the street naked hollering 'EUREKA' to all and sundry!).

I'd been having so much trouble trying to find the source of a continual back-firing or 'spitting-back' into my carbies on the GS1000 I've been rebuilding. Tried everything... eliminated coils, spark plug leads, the spark plug caps, the spark plugs themselves, the points, the condensers, the wiring circuitry, and dismantled and cleaned every nook and cranny of those VM28's three times over... and still no fix!

But then I did what you suggested, and used the Gunson 'Colortune' plug to tweak the air screws at 4000rpm, and the erratic spitting-back has just about disappeared! Still does it a touch when warming up on choke, but once warmed up she's right as rain, and the spitting-back on a light throttle at about 3000rpm has all but gone.

So Chuck -- your inadvertent words have been, and I'm not ashamed to say it, an answer to prayer. Thanks be to God, who even cares about us when we're fiddling with motorcycles!
 
I had the same popping problem too so I decided to buy the colortune. The pilot was fine but still the popping, so I decided to try the mixture screws and came to a nice smooth engine. I found that if you run her up and get it just so theres a blue flame and then add 1/8 more turn shes pretty rock solid.

Keeps it just "on the edge" of being rich..which if youll notice when watching the colortune is when the yellow flicker hits that it sputters.
 
Chuck:
How did you get the porcelain out of the plug? I have a "partially" dismantled plug on the bench, but can't seem to get the porcelain out of the plug recess.
 
I snapped the top off and them ground down the "rolled over" edge thatb traps the porcelan. Then straighten out the bent electrode and smacked it with an old drill bit..pops right out.

Maybe why my epoxy didnt fly out like that one guys did is that i welded around the hole once i got the porcelan out . That made a dam against it blowing out i suppose. Just a few tack welds around the rim will trap it well i suppose.

I think the real deal is way superior though.
 
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