Hey, thanks for this. I'm not confident it is just one cylinder. I've changed the plugs. They do get dirty in short order. I hadn't thought of a valve problem.
1971 T100C Refresh
- Thread starter Sundance
- Start date
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So I switched HT leads and the bike runs the same, so not just one cylinder.
Here is a link to a YouTube video of my bike running today - in case any members can diagnose from the video. Thanks!
View: https://youtu.be/iEbohJkz0lU
Here is a link to a YouTube video of my bike running today - in case any members can diagnose from the video. Thanks!
View: https://youtu.be/iEbohJkz0lU
I'm not an expert. Also, your lack of silencers means I can't distinguish whether it's cracking because of that or something else.
As well as a valve, it might be a head gasket going, cylinders leaking into each other.
Valves and head gasket can tested with a leak down test, if you have a compressor.
Here's a video I posted for someone else recently...
View: https://m.youtube.com/watch?v=rZ8iDHice0E
As I suggested in post #57, if you read the whole thread (and looked at the photos the o.p. has posted) you would not extend the thread with mistakes or suggestions that have been made already? The o.p.'s photos show the bike has silencers (possibly in the widest sense of the word ...) and:-
If you read the thread, while the o.p. has posted he changed the float - assuming to a StayUp although the o.p. has not confirmed that - he has not posted that either he reset the level for a Stay Up or has checked the fuel level.
So there are several things the o.p. needs to post confirmation before "can't seeing it being carb/fuel/air".
While posted symptoms don't suggest a leaking valve, the o.p. could post confirmation he has checked the valve clearances ...
A leakdown test might be necessary.
I very strongly advise against running an engine with HT leads disconnected from spark plugs - it was a stupid idea when Triumph suggested it in manuals for bikes with points; with e.i., there is a real risk of toasting the electronics.
As I posted for you earlier, a single Volts measurement is useless, particularly if it is taken with all switches off (the battery is not supplying a load). To rule out the battery as a cause, please confirm battery Volts at all three stages I suggested.
If the bike misfires the same irrespective of whether the ignition switch is in circuit or bypassed, how do you work out the ignition switch is a problem?
Please confirm the Transistor Box Red wire is connected as I have suggested.
Please confirm the wire from the second coil's +ve terminal is connected as I have suggested.
Please confirm you have checked all terminals (male and female) in the ignition circuit for tightness. This includes connections in the Black/White and Black/Yellow wires between the Transistor Box and the (Boyer) "Stator" in the original points compartment.
Checking terminals tightness is particularly important if the e.i. fitter used the common hardware store pre-insulated red-insulated terminals.
At this stage, very possible. But you are not going to find the cause(s) unless you positively-eliminate all possibilities?
The OP was stating it was a problem in one cylinder only. I pointed out if it persisted unchanged by swapping the HT leads, and given it's a single carb, that would likely rule out e.i. and carb issues. The OP has now conceded it's not necessarily one cylinder. Hasn't though specifically stated if one or both plugs foul.
The miniscule silencers, for me, are so loud and raspy, I can't tell anything by listening to the video. (Proper) silencers can also help with lower-rev running. There's plenty of older riders on this forum with deafness caused by loud-sound exposure; I'd fit reasonable silencers.
suzook12
Well-Known Member
I didn't have numerous hours to research the op. This thread is about a rough running T100 that has now lost spark! Having spent years making a living out of fixing bikes, assume nothing is my goto stance, so even if it was all over the net, I would still ask......
Thankyou@ Boyer
Ok cool, that's what I wanted to know, as if he had a trispark, red light could have been on the box.
Not entirely, the coil wires from the EI are a switched negative (Black), there is also a fixed negative (White) and a fixed positive (Red) from the EI itself.. Any e.i., coils are supplied by the e.i. O.p. has posted, "plenty of power at the battery and the coils" so we both await clarification of "plenty" ...
IGNITION ON-
White (as close to EI as poss) to batt + needs to be over 10V (mk4/ mk 3 12v) minimum.
Red (coil supply) to batt neg needs to be over 10V (mk4/ mk3 12v)
Red (EI supply) to batt neg needs to be over 10V (mk4/ mk3 12v)
not sure what time the EI switches off if engine static so repeated kicking may be required to see spark.
As the ignition switch is now being called into question, the fault may have been found. It should also be highlighted by supply voltages as mentioned above.
If you still suspect electrical issues, try fitting a one off harness ignition only and see if that fixes it.....
The signal generation can be checked if you DMM has a Hz setting. Disconnect tyhe black/white and black/yellow and test between those and engine while kicking over (Ignition off). You should see a reading of maybe as high as 10Hz, maybe more depending on how fast you can kick and the kickstand gearing. Resistance for each pulse coil should be 66 ohms.
Make sure there are no shorts between the wires and frame/engine on the pulser wires or you will lose spark. Check primary resistance of the coils you have fitted, no less than 3.5ohms combined
Installation instructions - http://www.boyerbransden.com/pdf/KIT00052.pdf
It could also be worth checking the rotor hasn't slipped and the timing retarded due to it.....
Start with the voltages 1st. Check again while running where possible.
Steve
Yes entirely:-
. DC is always from negative and to positive.
. Boyer (and licensed copies Pazon, Wassell and Sparx), the Transistor Box (or whatever the other three call it) White wire is always connected to battery -ve; positive earth electrics as on the o.p.'s bike, through the bike's switches.
. Correct.
. Incorrect. The Transistor Box Red wire is nothing to do with any coil/s connected to the Transistor Box Black wire.
. Do not be misled by any circuit diagram showing the Transistor Box Red wire connected to a coil terminal. Positive earth electrics (as on the o.p.'s bike), ideally the Transistor Box Red wire should be connected directly to the battery +ve terminal.
. In the slightly weird world of electronics, the Red wire is actually the supply to the Transistor Box electronics. This is the reason I pass on the advice of Ernie Bransden (and similar from a guy called John Carpenter, whose company used to handle all aftermarket sales and all servicing of the contemporary Rita e.i. for the original Lucas company, and similar from a third electronics engineer who posts on another forum), to connect the Transistor Box Red wire directly to the battery +ve terminal.
. The reason for this advice is it reduces the possibility of voltage spikes generated by other electrical components (not least the ignition coil/s) connected to the loom Red wires and to other bits of bike from affecting the Transistor Box electronics.
This is confused:-
. Transistor Box White wire is always connected to battery -ve, whether through the bike's switches ('positive earth' electrics) or directly to the battery -ve terminal ('negative earth' electrics).
. As above, Transistor Box Red wire is never anything to do with any ignition coil/s. Connecting it to a/the coil +ve and then to "Frame ground" or similar on wiring diagrams only increases the likelihood of the Box electronics receiving interference from other electrical components on the bike.
. Because the Transistor Box Red wire is always connected to battery +ve, it can only be the Transistor Box electronics' supply, never the coil/s supply.
Ime, it can be as short as two seconds.
However, on a Triumph twin, if the rider uses the legendary "long swinging kick", while the first piston on compression might not receive a spark, the other piston on compression should do. At worst, if the rider moves a piston just past compression before using the "long swinging kick", it should negate the e.i. switching off.Post #59:-
Positive earth electrics:-
. Ideally, the voltage measured between the Transistor Box White wire connection to the loom and battery +ve should be the same as the voltage measured between battery -ve and battery +ve when at least the ignition is turned on. Ime, it is better to let the o.p. measure and post these, only attempt to diagnose if the o.p. posts two different measurements.
. Measuring voltage between the second coil's +ve terminal and battery -ve could highlight additional resistance between the second coil's +ve terminal and battery +ve.
. Transistor Box Red wire, the advice I always pass on is to connect it to the battery +ve terminal itself.
suzook12
Well-Known Member
So we are led to believe. However it's not entirely true. Ive been told this twice now by USAAF and RAF electronics engineers. They tried to explain the science but way above my pay grade.... You have taken what I said out of context. There are 2 negatives out of the box. If either was corroded or damaged near the box end, no spark...
You have assumed, unless you have intimate knowledge,that's how he has connected it. I've not seen it or had the opportunity to trace his wiring harness. It doesn't run, assume nothing
Never said it did. There is a red to the box that needs testing and a red to the coils that needs testing.
As long as voltage drop is adequately dealt with, it doesn't really matter. GSX-R's and numerous others have never suffered because of it
Now, being from the world of negative earth, to me that's normal anyway
Interesting. The whole point of using an "earth" system whether negative or positive, is it uses the vehicle as a capacitor. This in effect irons out any spikes in the power supply. This is partly why car manufacturers run numerous "earth" points and wire between them as well. Motorcycles tend to do this less, but they do still utilise frame earth points and hard wire between them. Now RF interference is another matter and can require all sorts of filters to overcome
That part was an unknown to me, I know they time out, as read up on them as looking to fit one to my own bike. 2 seconds does sound a wee bit short, but they seem to work....Ime, it can be as short as two seconds.
I understand your reasoning, but this is seldom the case but usually near enough. There will be some voltage drop along the way but "should" be negligeable. However, the point of testing it, is to find out why the bike is no spark. If he has got this far, then it's fairly certain he has yet to find the issue.... I'm trying to ascertain why the bike isn't firing and why it was running rough before coil changes. I have a hunch it's the ignition switch causing a massive voltage drop....... But I wouldn't assume it until I have tried to disprove it
It could, but as it ran poorly before these coils were fitted, 1st coil reading should suffice. Resistance across both primary's should be in the order of 4-6 ohms (6V coils wired in series).
That's where I would be looking. Any voltage drops to box or coils can and will cause what the op is suffering.
Good luck to the op, hope he finds the cause#
You have an example applicable to these bikes of when it is not?
Not intentionally. However, this thread was started by @Sundance looking for help to solve an apparent misfiring problem.
Yes and no.
The Box White wire is not "out of", it is for the the negative supply from the battery -ve. Unlike, say, the ignition switch, the Box will not work if you connect the Black wire to battery -ve and the White wire to a/the coil -ve.
Post #1:-
... again, you should read the whole thread ...
If the engine starts and the bike is rideable, the Boyer Box can only be connected correctly.
The o.p. started this thread because bike has since developed a misfire.
... and:-
As voltage drop would signify additional resistance and the Box electronics only draw about 250mA, there simply cannot be noticeable resistance between battery +ve and the Box.
This is another reason why it is unwise to connect the Box Red to a coil +ve terminal and then connect that to something other than the battery +ve terminal itself - increased opportunities for unwanted resistance to exist or develop.
A capacitor stores electricity from a charger then discharges it due to trigger, so you kind of hope not ...
Even if it was true, any Lucas or pattern wiring loom has a network of "earth" wires. This is far more long-term reliable than using a motorcycle frame and other cycle parts.
But, as posted already, the engine is firing and the o.p. has ridden the bike, it has only developed the intermittent misfire since. While I agree the ignition switch could be a cause, that the o.p. has posted the misfire develops irrespective of whether the Box is supplied through the ignition switch or directly from the battery -ve terminal - bypassing the ignition switch (and all other loom wiring) - currently points away from the ignition switch is the cause of the misfire.
Original Lucas 12V coils fitted with points had/have a primary resistance of about 3.5 Ohms. When the Boyer (and Lucas Rita) were developed in the later 1960's-early 1970's, points were what they were developed to replace. Multiple electrical components connected in series, their resistances are cumulative - then original Lucas 6V coils had a primary resistance of about 1.8 Ohms, so two connected in series are nearly 3.5 Ohms.
The reason for 3.5 Ohms is a nominal 12V across 3.5 Ohms, the coil/s will draw approximately 3.5 Amps. From the Boyer fitting instructions for a Triumph twin with 12V electrics:-
Two "6V" coils connected in series, 4 Ohms total primary resistance is fine. However, increasing primary resistance reduces Amps drawn; as high as 6 Ohms, nominal 12V across the combination, it will draw just 2 Amps.
High coil primary resistance causing low Amps draw has been a well known cause of misfiring problems, especially at higher rpm, for well over forty years to my certain knowledge."Lucas" is now just a name used by Wassell on the electrical components it has made in low-wage Far Eastern countries. It is well known already that current new "Lucas" "6V" coils have much too high primary resistance to be used with any e.i. without problems.
The only coils with the correct primary resistance (12V 3.5 Ohm, 6V 1.8 Ohm, 4V 1.2 Ohm) and with backup if they go wrong are PVL and Tri-Spark.
Not sure why you quoted my post. The OP properly responded to my question.
If you read the relevant post - #64 - you'll see I quoted you because you had already posted the suggestion.
