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MikeG
MikeG
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I'm currently running a Boyer ignition on my '76 T140V. No complaints, it performs just as well as the stock points. But after a recent conversation with my dad (who has been doing many upgrades to his '77 MGB - original owner), there's electronic ignition kits available for classic cars that allow fully customized/programmable ignition curves. I searched around online and aside for some Harley specific applications there isn't much for smaller engines/motorcycles.
I would normally leave well enough alone but I've always felt my T140 loses a lot of torque as the revs build. I've had the top end apart and it's evident that this engine was designed to breath and setting the AMAL carbs is a well documented procedure. So this isn't and air/fuel problem. I'm convinced that a remapped ignition curve would really give this bike much more on the top of the tach.
Are all electronic ignitions using the same curve, does one give more HP over the others?
Is there an ignition module out there for these bikes that will let me screw around with the curve?
I'd love to hear your thoughts.

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The loss of torque at high RPM on the T140 is unlikely due to ignition lead. It has more to do with cam selection and cam timing. Plenty has been written about this; there are some things you could do to improve the performance that is minimally invasive but a new exhaust cam is likely the best solution in my opinion.

I ran the same Boyer ignition box on a stock T140 engine and a mildly modded engine with the same ignition lead. Cam choice and timing were all it needed to wake it up.

Last edited by mondtster; 06/14/21 10:42 pm.
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On the subject of ignition timing, at high rpm, above 5000 rpm or so, the Boyer is fully advanced and should not affect performance. However, I have always thought (without any real knowledge or investigation on my part, just feels this way to me)---that the Boyer ignition curve is too slow to get to full advance, thus affecting power off idle and in the mid range, not on the top end, and that this makes the engine feel just a little lazy in acceleration compared to the stock points advance curve.

One thing, though—make sure you are getting full voltage without loss to corroded switches/wiring connections/battery/charging system. This seems to affect the Boyer a lot.

On cam timing, I also retimed the intake cam on my T140 and it improved overall performance. There's lots of info out there about this, and here is just one: https://vintagebikemagazine.com/technical-articles/triumph-t140-cam-timing/ For more, just use the search function here, or search "T140 cam timing Britbike forum" on Google, and especially look for comments by Pete, the author of the article.

Last edited by linker48x; 06/15/21 5:29 am.
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Hi Guys, It's easy to see timing curve. Put paint dot on rotor with TDC tool in TDC slot in flywheel. Dot 38b line with paint. Split difference a few times with paint lines. Mark them with felt pin or like. Start motor.

You'll very quickly see how timing curve reacts to rpm.

With points you'll see how timing can jump around at lower rpm before full advance. The 38b at 2000 from AAU gives a little snapper feel.

The EI advance much more slowly. Really reduces ping at lower rpm. A very good advantage.

Trispark with idle stabilization is most fun to watch. It really works well & can react so quickly if motor wants to stall. It makes it start when normally it would have stalled at kick starting. Remarkable really. Also letting out clutch without giving enough throttle, it does it's best to compensate & keep from killing motor.

I found I got lazy really quickly. Going back to points motor you realize how well the Trispark actually works. Nice it doesn't take up space on on bike with EI box. All electronics are in the pick up plate in points cavity. Nice!!

I need to get a really nice timing light with both RPM & timing advance readings. Always put large fan in front of motor when playing with timing. Motor overheats fast other wise.
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Do the cam timing for lobe centres about 100 inlet and 105 exhaust, you'll be amazed. I've got a relatively simple (no DTI needed) procedure posted on the technical section of the Triumph RAT forum, or PM me and I'll send it to you.
cheers,
Mick.

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Several of us here have found the stock intake cam timing lobe centers to be about 90-92 degrees... When retimed to 100 or so it reduces lower speed cylinder pressure and the tendency to ping...It's that simple and the engine performance is noticeably improved.


79 T140D, 89 Honda 650NT ,61 A10 .On a bike you can out run the demons
"I don't know what the world may need
But a V8 engine is a good start for me
Think I'll drive to find a place, to be surly"
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A t140 exhaust cam is softer than the t120. Hotting it up is worth it, and fit the 3 piece bearing.

I understand that John Healy is the importer of Boyers? And that he said he can arrange to change the curve?

I use a Pazon - I understood at the time that one advantage was a better curve?

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Hi Mr. Bean,

If the price is no problem this device offers a selection of 9 curves https://www.elektronik-sachse.de/manuals/Z15-3.12-en.pdf
They also offer an alternative with 3 curves only :-)

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Originally Posted by Jouko
Hi Mr. Bean,

If the price is no problem this device offers a selection of 9 curves https://www.elektronik-sachse.de/manuals/Z15-3.12-en.pdf
They also offer an alternative with 3 curves only :-)

303 € , thats not a bad price
https://www.elektronik-sachse.de/sh...3-12-for-bsa-norton-triumph-enfield.html
[Linked Image from elektronik-sachse.de]

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“I'm currently running a Boyer ignition on my '76 T140V. No complaints, it performs just as well as the stock points.”

As the stock points and EI end up at similar advance above ~4k or 5k rpm, you shouldn’t notice much difference at higher rpm.

It is at lower rpm that you will notice a difference.
Points/AAU will reach full advance at lower rpm than Boyer (and most other analogue EI).
Typically points achieve full advance ~2500rpm, typical analogue EI’s ~4000-5000rpm.

If running a sporting engine (say ~9:1 compression) the more relaxed curve of EI may help avoid detonation at lower rpm (especially with modern fuel).

All ignition systems should provide the spark at the same timing at high rpm (which is where you say is where you are losing grunt).
Changing the advance curve won’t change this, it can only change how it performs at lower rpm.

Listen to the folks experienced with cam timing, that can change where your engine buzzes.
One thing I have used are the simple old fashioned Megaton reverse cone “silencers”. They make a Triumph truly fly. Avoid the cheap look-alikes, they don’t work.

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knuckle head
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Originally Posted by AngloBike
A t140 exhaust cam is softer than the t120. Hotting it up is worth it, and fit the 3 piece bearing.

I understand that John Healy is the importer of Boyers? And that he said he can arrange to change the curve?

I use a Pazon - I understood at the time that one advantage was a better curve?
You have to have the Boyer advance rate changed before place the order. I just went through this. , it's a post in the General Forum ...John Healy sells wholesale only but he will be glad to repair an existing Boyer but cannot change the avance on an existing unit. bought the Boyer Micro power that features a fast advance curve and other features.Costs about twice the entry level Boyer.My bike's engine has a few modifications with stock parts to increase power with no detonation issues on mid grade pump gas..


79 T140D, 89 Honda 650NT ,61 A10 .On a bike you can out run the demons
"I don't know what the world may need
But a V8 engine is a good start for me
Think I'll drive to find a place, to be surly"

Moderated by  John Healy 

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