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#247551 - 04/10/09 1:00 pm spark plug collour  
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Ger B Offline
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Ger B  Offline
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After reading Ducknaldo's thread about plug chop I still wonder: how long does it take new plugs, straight from the box, to grow a collour that can be diagnosed. Would 50-kms (35 miles) be enough?
I started this morning with a new carburettor and two new plugs, and I'm in doubt...


Ger B

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#247559 - 04/10/09 1:19 pm Re: spark plug collour [Re: Ger B]  
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Alex Offline
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Seattle
Don't know which thread you are referring to, but the mixture ring will form in a few seconds once the plug and engine are up to temperature. The general color of the insulator is pretty meaningless unless you're running way too rich or burning oil.


A smattering:
'53 Gold Flash
'67 Royal Star
'71 Rickman Metisse
'40 Silver Star
'37 Rudge Special
sixtyseventy Lightboltrocket road racer...and many more.
#247563 - 04/10/09 1:30 pm Re: spark plug collour [Re: Alex]  
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Ger B Offline
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Ger B  Offline
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This is what I found after 50 km, part motorway, part citytraffic and part secondary road.





Ger B

#247570 - 04/10/09 2:14 pm Re: spark plug collour [Re: Ger B]  
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Dave Comeau Offline
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Dave Comeau  Offline
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Hamilton, Mass. USA
Ger
From running air cooled motorcycles on my chassis dyno, I have found the plugs show the results of whatever happened in the last minute or so of what was going on inside the engine.
If you have a carb that is fouling the plugs in city driving (bad needle jet) the plug will be black...then WOT like highway conditions, then the plug will clean right up tan/white or what ever is the expected result at that engine condition and plug temp & heat range.
Even with new plugs on the same engine they will again show black for city driving and clean up under heavy hi temp loading.
Therefore to answer your question, in 35 miles your plug color could change many times depending on your driving pattern. The The plug color is just evidence of recent past history of the engine laoding.

I haven't bought plugs in many many years. I use other peoples throw aways. I put them in black and after use, they are soon burned clean.
2
Dave


dynodave
BSA 3 1961-1963
Ducati 3 1992-2002
Norton many 1951-1975
87 Serv-Equip 100HP MC brake dynamometer,
#247572 - 04/10/09 2:21 pm Re: spark plug collour [Re: Ger B]  
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Alex Offline
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Seattle
Ger, the only things you can tell just by looking at the plugs without any aid is a)the plugs are in the right heat range by a line formed on the electrode b)if you see specks (peppering) on the insulator, you're detonating and c)burning of the electode indicating detonation.

To judge mixture, you need to be able to look at the base of the insulator. Two ways to do this are to either cut the threaded portion of the plug off with a hacksaw or get an otoscope (Plug reader) to look into the plug. The brown color on the insulator is not a good indicator because it varies widely with fuel additives and is too qualitative. When you look at the base of the insulator, you want to see a dark ring about 1-2 mm in width. That generally indicates an ideal mixture. No mixture ring indicates lean running, a wider ring indicates rich.


I've posted this many times before, but some of you may not have read it. If you really want to tune carburettors, it is essential IMHO, that you know how to read plugs.

Oh, and as Dave sez: your plug only tells you about the last throttle position you used. Hence the term "plug chop". You need to cut the motor off while running in the throttle position you want to tune.

Last edited by Alex; 04/10/09 2:25 pm.

A smattering:
'53 Gold Flash
'67 Royal Star
'71 Rickman Metisse
'40 Silver Star
'37 Rudge Special
sixtyseventy Lightboltrocket road racer...and many more.
#247631 - 04/10/09 7:43 pm Re: spark plug collour [Re: Alex]  
Joined: Mar 2005
Posts: 9,965
John Healy Online content
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Boston, Massachusetts
I cut and pasted this from the Triumph forum so the reference to the plug color and being rich is relative to the question asked on that from, but I think it is relevant here:

Mike Canter is a prolific technical writer with credentials to back him up...

http://www.dragstuff.com/techarticles/reading-spark-plugs.html

You asked a simple question, that does not have a simple answer.

But simply stated you should run the plug recommended by Triumph unless you have conditions or circumstances that dictate a change.

Modifications to the motor or changes in fuel, working environment or ridding style can be a reason for changing from the recommended plug.

As far as your very light brown/grey color reading for what I believe you mean when you tell us you did a plug chop, would lead me to believe that you main jet is too big... Kill motor after running the motor at or close to full throttle. But you seldom ride at or close to full throttle. I don't think it is so rich to be of concern, but if you were looking for full power I would lean it out a tad. Until the little ring Mike forms on the base of the insulator as mike describes in his article.

Now we need to check the needle/needle jet circuit and slide cutaway where you ride the bike 80% or more of the time. Read what Mike has to say about that and where to look, and why.
John


Last edited by John Healy; 04/10/09 7:45 pm.

#247633 - 04/10/09 8:02 pm Re: spark plug collour [Re: John Healy]  
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Geoff Online content
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Indianapolis
On a side note but still on topic - has anyone used the colour tune kit with the transparent plug that enables you to see the combustion? Is it a gimmick or can something like that actually work?


'78 T140V
'74 Commando
'71 A65L - Cafe in progress now almost 20 years!
'69 TR6R
'58 Allstate (Puch) 175
#247644 - 04/10/09 8:50 pm Re: spark plug collour [Re: Geoff]  
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Ger B Offline
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NL
I pulled the plugs after I made a first ride out of the village with a new carburettor (JRC flat slide). Earlier they were a bit sooty after idling in the shed and after some short rides inside the village, with low speed. So today was the first opportunity to take it for a longer ride. The collour is based on the last leg home wich is 2 km (a slice more than a mile) of 50 kpu (30 mph) straight (with three speeding camera's).
On the motorway, above 110 kpu (65 mph) he bike hesitated and did not want to go faster. It never did that with the AMAL.
But something between my ears says it's not the jetting of the JRC, but ignition. The engine also kicks back in the kickstarter, which it never did before. Ignition is Boyer MK-3.
The stator with the two small coils is still in the same position as ever. Battery voltage is 12.5 standing still going up to 13+ when the engine runs with lights on.
I thought maybe the plugs would say something.
What is an acceptabele life time for a Boyer?


Ger B

#247651 - 04/10/09 9:17 pm Re: spark plug collour [Re: Ger B]  
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Blapper Offline
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Kent UK
Ger,

Have you changed anything to do with the ignition or electrics at the same time or since you changed the carb? Have you had anybody else help you with what jet sizes you need in that carb?

Blapper redwine

#247659 - 04/10/09 10:06 pm Re: spark plug collour [Re: Blapper]  
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Ger B Offline
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The only change in electrics was: new plugs, same spec as the old ones, gap set to 0.7 mm as per instructions. After my accident last year I did not ride much. The left shoulder was to painfull. So practically you can say it has been standing since september in a moist cold shed. That cannot be good for electronics trapped in a box filled with cast resin; I think.

The carburettor was jetted by JRC. A mate of mine drove the bike this morning. He's a professional classic mechanic. We managed to turn idle speed down to around 750 / 800 rpm. Beautifull, like a marine diesel. No hick ups speeding away from traffic lights. The bike pulls like a locomotive through all gears so no reason to suspect jetting. But on the way back from the center of Den Haag to where I live between Den Haag and Rotterdam I discovered in fourth gear it starts to hesitate above 110 kpu, which is embarassing when you try to overtake a white van.


Ger B

#247661 - 04/10/09 10:10 pm Re: spark plug collour [Re: Ger B]  
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Russ Hunt Offline
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PA
Boyer lifetime: My Boyer has lasted 35 years and still going strong.

#247729 - 04/11/09 8:24 am Re: spark plug collour [Re: Russ Hunt]  
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Ger B Offline
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Ger B  Offline
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Cheapest and easiest thing to do is to concentrate on the main jet and needle hight, I think.

Thank you all.


Ger B

#247738 - 04/11/09 10:04 am Re: spark plug collour [Re: Ger B]  
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Blapper Offline
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I agree with that course of action Ger.

Encapsulated electronics are not affected by the conditions you mention.

Blapper redwine

#247741 - 04/11/09 10:27 am Re: spark plug collour [Re: Blapper]  
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Ger B Offline
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not infected... wel... I've seen some bad E-motor windings on board of ships; but to stay by the rule: what has been changed is the first thing to suspect when things do not work fine. So I screwed the main jet out of the JRC and found it was size 140. The main jet in my AMAL was 230.
So mayby JRC jetted this carb for twin carburettor use.

I'll pick up a few larger JRC jets this evening, when my mate is back from watching cars in a car exhibition.

Enjoy Easter, and do not forget to eat enough eggs.


Ger B

#247896 - 04/12/09 1:16 pm Re: spark plug collour [Re: Geoff]  
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maylar Offline
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Connecticut
Originally Posted By: Geoff
On a side note but still on topic - has anyone used the colour tune kit with the transparent plug that enables you to see the combustion? Is it a gimmick or can something like that actually work?


My brother bought one to set the idle mixture on a 4 cyl Yammie. After 5 minutes the damm thing melted. The glass window part was OK but the plastic shroud tube that lets you see the flame became a molten blob.

I never got to try it on my Norton. frown


Dave from CT
#247902 - 04/12/09 1:44 pm Re: spark plug collour [Re: maylar]  
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Alex Offline
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Seattle
The colortune only works for idle mixture tuning. With that limitation in mind, I know several people who have used it effectively.

Ger, it is not hard to do a plug chop. Read the articles that John Healy and I posted and you can eliminate the carb as a source of trouble. Even through extreme abuse, I have yet to have a Boyer fail. That said, low voltage can make life with a Boyer hell. My Royal Star holed two pistons because the stator wire had chafed through on the stator and would arc at high RPM so the battery would never charge...but it would never die either. Timing was affected, but not at idle and there was no short in the stator wires that could be measured statically. Eventually it got so bad that the pistons got holed. Also, I know of many people having Boyer problems because of bad power connections. Moral of the story: check voltage at the Boyer...while you're riding if you can.


A smattering:
'53 Gold Flash
'67 Royal Star
'71 Rickman Metisse
'40 Silver Star
'37 Rudge Special
sixtyseventy Lightboltrocket road racer...and many more.
#247909 - 04/12/09 2:22 pm Re: spark plug collour [Re: Alex]  
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Mr Mike Offline
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Ger,
I have no qualifications or experience wtih a JRC. A friend put one on a Triumph 500 with good results except the factory setup required changes. I do not recall the changes. From your description, and little other info, I would guess your are either too rich on the main (if it stutters) or too lean if it just has no power. Is the only problem at above 3/4 throttle opening and OK. Also I would not think that different carbs (amals, Miks or JRC) would necessarily use the same main jet. When I put a Mik on my B44 it ran four main jet sizes smaller than an AMAL of the same bore. It stuttered badly with too big a main jet. Once I got the right size it was perfect and thru all of my main jet changes, the rest of the range from idle to 3/4 was perfect.

Mr Mike

#247932 - 04/12/09 4:51 pm Re: spark plug collour [Re: Mr Mike]  
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Ger B Offline
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In circumstances like this I miss the theoretical background which I do have with marine diesel engines. And believe me: I think petrol engines are more complicated than diesels. But you fellows recommended some ineresting reading material.

When I passed the van on the motorway, yesterday, and the bike hesitated, my first idea was: fuel starvation. But when I arrived home, some ten minutes later, and pulled the plugs, these had a black ring (see photo in earlier post). That confused me, as I had expected a nearly clean ring. But, as I learned here: the black is the result of the last leg of the ride, which is a long narrow road with a 50 kpu (30 mph) speed limit and three speeding camera's. So that spoiled my idea about fuel starvation. That, plus the fact that the bike had kicked back in the kickstarter gave me the idea that the ignition might be the sinner.

But as the cheapest way to work would be to start with the carburettor that is what I did. Apperently (spelling?) the main jet 140 is the largest JRC has (at least my mate had only smaller jets in the bag he received from mr Getty). And looking at it, the hole in it seems not much smaller or larger than the hole in a 230 AMAL jet. So today I opened the carb and lifted the needle. It has five grooves. The circlip was in the middle groove. So I inserted the circlip to the lowest groove.
Mistake. The starter kicked back more violently, the exhausts smoked like the chimny of a coal fired tugboat and the engine would not idle, whatever I did.
With the circlip up one groove it started better: no more kick back, no more black smoke, and I was able to turn down the idle speed again to about 750 rpm.

I'll test ride tomorrow, wondering why a needle job involves:

1 remove fuel tank
2 remove bolts and nuts that hold airbox halves together
3 remove left part of airbox
4 remove right part of airbox
5 remove carburettor
6 open air slide cover...

Thank you all.

Enjoy Easter.


Ger B

#248054 - 04/13/09 11:56 am Re: spark plug collour [Re: Ger B]  
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Mr Mike Offline
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Cape Carteret, NC
Ger,
Marine diesels are marvelous engines for what they must accomplish. They are capable of moving many tons of freight at very low cost when compared to vehicular transportation. For the most part they run at constant rpm, at constant temperature and a uniform load. They can literally run many, many years with routine oil and fuel filter changes. Our BSA's must run in a wide rpm range, accelerate smartly, operate in wide varying temperature ranges and under many different loads....a much taller task than you marine diesel.

I am quite sure your problems are in carburetion. As Alex says reading spark plugs is complicated, but you if it is all sooty or dark black it is to rich and if it is white and pops back in the carb it is too lean. Since your problem appears to be at open throttle postions, drop a jet size to see what happens. The real proof is in how well the bike performs, not so much the colour of you plugs. When you get it right the plug will be between tan and brown, but will darken up when you idle thru town and lighten up after a long ride at highway speeds. I know this is a JRC carb but print a copy of the AMAL guide on this website a study it. The principles are pretty much the same.

Mr Mike


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