konrad

It's possible the system does not operate as I had guessed. Perhaps the CDI utilizes a DC-DC converter? That would explain the relatively low voltage observed. Can you post a picture of your stator?

Really? I would expect the disconnected (unloaded) reading to be higher than the connected (loaded) reading.

Compliments on your testing and reporting skills! That resistance indicates a fairly robust wire diameter that would be less likely to fail than a much finer wire. The results you saw when heating the coil also indicate it is not likely to be the problem. You would need special test equipment and "ring" the coil in order to test for a few shorted turns. cascade1imp quoted a reading of 20 - 30 VAC (no peak reading adapter) on the exciter coil when kicking. (Was this with the CDI connected, or not?) If no one is willing to build your peak reading adapter (with a 4.7 uF capacitor) and test their bike, this may be the best information you will get.

One of the drawbacks of trying to quantify the AC voltage produced by a motorcycle stator coil is that the waveform is nothing like a sinusoid, and different meters will measure it differently. That makes a compelling reason to buy or build a peak detector. See: https://thumpertalk.com/forums/topic/1034259-build-your-own-peak-voltage-adapter/A Although be aware that different values of the resistor and capacitor (and the input impedance of the meter itself) can give rise to different readings as well. That's all I can contribute for a while, as I'm off to do a trials now.

Excellent question! And, at what temperature is it being measured? Although resistance readings can help find a defective coil, they can't guarantee proper operation. I expect your exciter coil will be comprised of many turns of fairly fine wire. Even a few shorted turns will cause it not to work properly, yet the resistance reading will be essentially unchanged. The fact that your pickup coil was inoperable also may be a clue to damage by water. Another test is to measure the resistance of the suspect coil while heating it with something like a hair dryer. Copper wire has a positive temperature coefficient of ~0.4% per degree C. You should see the coil's resistance increase gradually as you heat it. If, however, the resistance drops suddenly, this indicates a problem.

The two power coils in the alternator are "floating" so there's nothing to ground (therefore corrosion of the alternator cover bolts can't cause your problem). The G/W wire from the ignition pulse generator connecting internal to the CDI ground wire is not necessarily a problem (and would be unlikely to cause the intermittent symptoms you describe).

Probably would not hurt to post a scan/photo/screenshot of your wiring diagram, as I am not familiar with that system.

Also, try measuring the peak exciter voltage with the CDI disconnected. The CDI may be loading that coil too heavily.

When kicking, can you correlate a spark/no spark event with a difference in the peak output of your exciter coil?

I have no experience with this particular model, and I'm not sure about your nomenclature. But... for the winding that goes to the CDI (not to the voltage regulator) I would expect to see closer to 100V while kicking. How are you measuring the "peak" voltage? The output of that winding is dependent on RPM. I would suggest "motoring" the engine with an electric drill via the flywheel nut (you may have to get creative with a socket/adapter etc.) I generally do this with the head off, but just removing the spark plug may give you a clue. P.S. you've done a good job troubleshooting so far!

I would take issue with the reasoning behind that statement. Generally, a smaller bore will produce a higher air velocity thorough the carb which will help low-rpm response. If there is a low-rpm improvement with the Keihin / OKO it's because they are flat-slide-carbs (versus the Dellorto which uses a round slide). The smaller volume under the flat slide makes it respond quicker because fuel is pulled through the need jet quicker. A larger bore has the potential to flow more air for high-rpm use. On just bore size alone, a 28mm carb provides 16% more area than a 26mm carb. However, additionally, a flat-slide carb will flow more air than the same size round-slide carb.

One finger, and one finger only, always on the clutch lever. Ride a gear higher than you normally would. This will force you to quickly develop the skill.

Increasing lever free-play may have fixed it. At some point in the bike's life did you top-up the fluid and then later replace the pads? Trials reservoirs are small -- maybe there was not enough room for thermal expansion of the fluid. In any event, I would check for pad wear and evidence of them binding in the caliper; exercise the piston travel with the pads removed and clean everything; perform a fluid change.

The short answer is, no. I'm not a chemist and most of my reading on the topic has been on the combustion side. However, there is a criticism of ethanol I've been meaning to add and will take this opportunity to do so. It comes from the SAE book Alcohol as Motor Fuels (PT-19).

I buy lots of old books using BookFinder.com: https://www.bookfinder.com/ If you have the ISBN, it's easy! Not sure exactly what you are seeking, so I searched on Author "Clymer" and Title "Montesa". There were many results. EDIT: Hmm, can't seem to get that external link to be clickable. Just search "bookfinder".

Are you asking if he is using AvGas or suggesting that he do so? Below is a link to my write-up on leaded fuel:

Have you played with the ignition timing? Generally, advancing ignition timing will help bottom-end power/response at the expense of high-RPM power and possible detonation. I also find that a combustion chamber with minimal squish clearance and a sharper blend radius (both of which increase turbulence and therefore rate of combustion) will create a more explosive "hit."

Arbutus, thanks for sharing your solution. How does that modification affect the stand on hard ground, like your garage floor or driveway?

For me, it's mostly about consistency of use. None of my other bikes auto-retract (or at least they did not do so for long). Every other bike I've owned provided an easy means to defeat their auto-retract mechanism. P.S. I removed the inner spring thinking that might do the trick, but no luck. Not sure what that inner spring is supposed to accomplish -- maybe just Honda's "belt and suspenders" approach?

Jonny, thanks for the idea. The brackets are inexpensive: 0536-NN4-600 Bracket, Side Stand for ED/3E $18.63 USD 50536-NN4-D10 Bracket, Side Stand for 2E/4E $12.46 USD I wonder what the difference is? 3ED is the competition version, right?

Personally, I would not replace the original capacitor. There can be significant differences in the quality of electrolytic capacitors and some inexpensive brands have a very high failure rate. You can learn some of the generalities here: https://en.wikipedia.org/wiki/Capacitor_plague

Does anyone have a solution to this problem? I could not find anything via searching here. No defeat strategy appears obvious to me. I'm unwilling to pay Mitani's price, or to remove it completely. Has this been a "feature" since the bike's introduction? TIA.

Interesting. Is the transmission not vented at all? Maybe that's part of the problem? When the air/oil in the transmission expands, that can't make life easy for the crank seal.

I have no idea what a Dalesman is, but 25:1 seems like a lot of oil for any trials bike. It might take a while for the motor to clean itself out even with no gearbox oil being sucked in. You can test for a gearbox-side crank seal failure by replacing the transmission breather hose with several feet of clear plastic tubing and then submerging the free end in a jar of water. When you blip the throttle, a bad seal is indicated by bubbles in the jar, or water being sucked towards the transmission. It also might just be very, very rich.

I stumbled across this because of another thread. I'm guessing it's been too long for the OP to still care, but perhaps my response will help someone else. CDI = Capacitor Discharge Ignition. The factory wiring diagram is truly horrible, and you were smart to attempt to draw your own. In regard to your .PDF drawing: 1. That "run switch" configuration would be very unconventional (and I suspect it is incorrect -- especially because it would be required to "open" to kill). Typically, one side of the ignition coil would be permanently connected to earth. 2. Kill switches typically "close" to produce the kill function, and "open" for the run function. 3. The wire you have marked "Lights?" is unlikely to power the lights. There's no need to involve the CDI in that task. It's possible this is were a conventional kill switch would be connected (but more investigation would be prudent). 4. Lights typically are powered via the low-voltage winding on the stator that powers the fan.