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Discussion Starter #1 (Edited)
Hi all. Would appreciate some help with a 63 6T with Boyer ingnition:

Monday AM, after Sunday eve's two hour cruise around SoCal, the 6T decided to run on left cylinder only. After a couple of minutes idling right cylinder would fire every 15-20 secs for a couple of beats & then stop again.

Battery is good - 12.18VDC with engine off, lights will stay on for ages with motor off. Battery cells are all topped up.

Charging circuit is good : 13.6VDC on idle, 14.1 when revved.

Plugs have been swapped side to side.

Coil leads have been swapped side to side.

HERE'S THE WEIRD PART :

If I pull the right HT Cap (Spark Plug Cap) partly off so the spark has the jump from lead to top of spark plug, the right cylinder fires right up.

Im sure the last (weird) part will make my problem obvious to someone...just not me!

Appreciate any words of wisdom,

Thanks..
 

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You might as well do the two major wiring problem fixes on the boyer in the pick up area. I had to do both on mine but at different times. The wires come loose in the crimp connectors being the first.
Then the wires come loose at the solder connections on the circuit board. The crimp connector is an obvious fix. The circuit board you drill and use some small 4/40 or so screws and nuts. Brass ones are best I suppose. Also, make sure there is enough slck to account for engine movement on the wires exiting the pick area and going up to the coils.
 

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I had electronic Ignition in my Norton (Rita Lucas). When things started getting weird with the black box I put the points back in. I don't put a lot of miles on it and you can fix points on the side of the road.
 

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I had electronic Ignition in my Norton (Rita Lucas). When things started getting weird with the black box I put the points back in. I don't put a lot of miles on it and you can fix points on the side of the road.
Given that the electronic ignition systems cost 100 times more than the points system we ought to be getting one electronics problem to every 99 points questions. Does not seem to work like that. However it is easy now to call a tow truck on your mobile, not an option when the bikes were built. We have sacrificed survivability for longer maintenance intervals.... but even that is not so, we still have very similar plug life to the 1940's.

Here we have a problem made more complicated than it should be because of the introduction of more complexity. My first thought was a plug, but as those have been swapped, it could well be a coil beginning to break down. On a points system that is about the end of your fault finding trail ( bar the points which can be inspected, measured or replaced cheaply). So perhaps swap the coils..
 

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You might as well do the two major wiring problem fixes on the boyer in the pick up area. I had to do both on mine but at different times. The wires come loose in the crimp connectors being the first.
Then the wires come loose at the solder connections on the circuit board. The crimp connector is an obvious fix. The circuit board you drill and use some small 4/40 or so screws and nuts. Brass ones are best I suppose. Also, make sure there is enough slck to account for engine movement on the wires exiting the pick area and going up to the coils.
We experienced this in May 2007 on my friends MkIII 850 Commando. The wires get brittle where they come out of the circuit board. I think all he did was resolder them on (he's an electronics/vintage tube amp whiz.)
 

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Sounds like the spark plug is bad. When a spark plug is faulty, it requires a much greater voltage to spark as the resistance is very high. When you pulled the spark plug cap slightly away, you increased the gap and required the ignition to create a much higher voltage in order to jump the increased gap, thus firing the plug. Replace with Champion N3's. BTW, you can experience this with points also.
Just my $.02
TR6
 

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Too easy.

The spark plugs are fouling. Yes, you swapped them, but that just means you have them at the point where the environment in that "bad" cylinder will continue to misfire unless you install new plugs.

THEN, get your mixture right to avoid re-fouling.

For what it's worth, I see about 50 posts regarding issues with Boyer ignitions to every 1 post regarding issues with Sparx ignitions. I KNOW there are more than 50:1 Sparx ignitions installed out there. Personally, I have screwed with about a dozen Boyers and had issues with half of them, and about 20 Sparx units with zero issues.
 

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I had the exact same symptoms with my 68 T120.
The coils were not a matched pair. One was a SIBA and the other was off-brand TAIWAN I think. Any how, since they areconnected in series with Boyer ignition, I think one of the coils reponds differently.
The SIBA was on right side (I set ign timing off this one) TAI was on left side. Timing via strob was slightly retarded on left side. I coul slightly pull plug wire up and engine would respond. I swapped plugs, wires, symptom stayed with left coil.
Replace BOTH coils w/12v matched pair from local triumph dealer.
Prob solved. This just happened about 2 weekas ago.
 

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63 Tbird

Before you do anything put in new plugs. if the problem goes away even for a few minutes you've got it.
The Boyer fires both plugs together, and you only have one carb, so the problem can only be in the mechanics of the one cylinder.
Check all connections at the coils and the pickups. Boyers need a good voltage supply, your battery seems good, but make sure you aren't losing volts in the wiring.
Two 6 volt coils are best as they are wired in series. Two 12V coils will work but give a weaker spark due to the higher input resistance which may cause some mysterious odd running. Boyers like 3-6 ohms across the coils which is what you get with two 6V units. You could run hotter plugs in a 6T, Champion N4 or equivalent. The soft nature of your engine (7:1 comp ratio) means you will not hurt anything unless you are running wide open across the salt flats! Even with Bonnie pistons (9:1) you are probably OK.
In fact Triumph themselves recommended N5's in their late (7.5:1) 750's.
Good hunting, Todd
 
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