Let us compare notes...

xbacksideslider said:

If you are still running the stock mechanical automatic advance unit, that can be a problem for idle when it occasionally sticks in the advanced position, for instance when you roll up to a stop light.

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Wassel EI. I guess it could be the stator for it is slipping a bit?

Tornado said:

I guess the difficult part to explain is that the dips in rpm are not constantly bouncing from 500-1000. Its more like fine when setting idle at stand still, then fine for next number of minutes riding around. Thne at next throttle roll off with clutch in or at a stop light, I'll see 800-500...where it stays until after a few repeated blips. If it were a loose chain giving play in timing, then I'd think it should change with each change in crank speed....a constantly wavering idle rpm.

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I did see the same thing when I had a Boyer Mk4 mounted, but the Tri-Spark seems to have cured this. Idle is rock solid.

Tornado said:

Wassel EI. I guess it could be the stator for it is slipping a bit?

Click to expand...

Reading over the Wassel documentation, and looking at the hardware, it looks a lot like a copy of a Boyer - more of a solid state device rather than a digital ignition.

I have never really liked the Boyer-style pickup design, as it relies on generating a sine wave with the right frequency to match the engine speed, and since the cam it only turning a say +/- 400 rpm at idle, I can see this sine wave being a bit choppy... Not sure if that is a contributor?

The Tri-spark is a digital device - the pickup is more of a "switching" device, based on magnet proximity and angular velocity. A more consistent device in my opinion.

Disclaimer - mechanical engineer trying to make sense of electrons.... LOL

Derek Wilson said:

Reading over the Wassel documentation, and looking at the hardware, it looks a lot like a copy of a Boyer - more of a solid state device rather than a digital ignition.

I have never really liked the Boyer-style pickup design, as it relies on generating a sine wave with the right frequency to match the engine speed, and since the cam it only turning a say +/- 400 rpm at idle, I can see this sine wave being a bit choppy... Not sure if that is a contributor?

The Tri-spark is a digital device - the pickup is more of a "switching" device, based on magnet proximity and angular velocity. A more consistent device in my opinion.

Disclaimer - mechanical engineer trying to make sense of electrons.... LOL

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Agree the wassell unit is a boyer mkIII type box, but there are improvements as the stator is fully "potted" in epoxy, no/less risk of stress cracking the wires to it.
It has been pretty good since fitting three yrs ago. This issue with rpm dips seems a new occurrence after head rebuild and new carbs installed.

I"ll be checking/cleaning the kill switch contacts and going over some other items.
I run a charge voltage warning led (SparkBright) that seems to be showing low volts at various times of my rides. Not yet pinned down why. Batt is good. Connections good. Might be the stator/rotor or the Tympanium reg/rec.
Maybe this is messing with the EI, though Wassell has a pretty generous working voltage range.

Tornado said:

Agree the wassell unit is a boyer mkIII type box, but there are improvements as the stator is fully "potted" in epoxy, no/less risk of stress cracking the wires to it.
It has been pretty good since fitting three yrs ago. This issue with rpm dips seems a new occurrence after head rebuild and new carbs installed.

I"ll be checking/cleaning the kill switch contacts and going over some other items.
I run a charge voltage warning led (SparkBright) that seems to be showing low volts at various times of my rides. Not yet pinned down why. Batt is good. Connections good. Might be the stator/rotor or the Tympanium reg/rec.
Maybe this is messing with the EI, though Wassell has a pretty generous working voltage range.

Click to expand...

Easy way to check if the charging system is messing with you is to simply disconnect it, run off the battery for a short time and see if anything changes. (I recently ran into that with the Trispark and my Podtronics not liking each other - ended up switching back to the stock rectifier/zener setup, working fine now).

The only other thing I noticed in the Wassell documentation was the low end voltage range of 10 volts. You mentioned low volts being indicated - could you have a bad connection somewhere? The Lucas bullet connector female halves have a habit of fracturing over a period of time... ??

Process of elimination, I guess.

Derek Wilson said:

Easy way to check if the charging system is messing with you is to simply disconnect it, run off the battery for a short time and see if anything changes. (I recently ran into that with the Trispark and my Podtronics not liking each other - ended up switching back to the stock rectifier/zener setup, working fine now).

The only other thing I noticed in the Wassell documentation was the low end voltage range of 10 volts. You mentioned low volts being indicated - could you have a bad connection somewhere? The Lucas bullet connector female halves have a habit of fracturing over a period of time... ??

Process of elimination, I guess.

Click to expand...

When first noting the low volts indication, I had swapped headlight shells to a used one with some dodgy connections. I'd also taken the easy approach and just wired in the warning LED to connections within the shell....so thought that was the initial issue. I've recently run one line from the indicator LED to the main ground (+ve Earth) frame point where engine, EI at Earthed. Other line from LED goes to a switched on with ign line.

Need to make some tests while idling to check for AC output of my alt (oem lucas) and have a check with a multi meter of DC coming off the Typanium unit. Seems not many folks here use that simple reg/rec (all of $25 USD?). My Zener failed previously and bloated a battery one day....the 2MC got me home though...even started ok with the EI. just got dodgey using incandescent turn signals at the intersections.