konrad

If you don't get a better answer, I'll say that 0.002" is too tight for anything. I'm guessing it may be a misprint and should be 0.020" as the service limit. 0.012" seems roughly right for new rings. At the risk of stating the obvious, the purpose of the end gap is to allow clearance for expansion as the ring gets hot -- you do not want the ends to ever touch. Minimum end gap is a function of bore diameter and operating temperature. New end gap is typically on the order of 0.004" per inch of bore.

I don't know the answer, but you can download a Braktec trials catalog here: http://braktec.com/product/ I'm guessing the caliper looks like this: https://www.splatshop.co.uk/braktec-4-pot-front-brake-calliper-mono-black-red.html Have a look at EBC's FA644X pads: https://www.oreillyauto.com/detail/b/ebc-motorcycle-5876/brake-systems-16456/brake-pads-shoes-16515/brake-pads-12845/a99314144bb6/ebc-brakes-ebc-motorcycle-front-disc-brake-pads/fa644x/6095770

Are you measuring the secondary with or without the resistor cap (which is typicality about 5000 ohms)? Resistance reading don't tell the whole story. https://www.trialscentral.com/forums/topic/70835-montesa-cota-315r-no-spark-issue/ CDI ignition coils are fairly universal - a better way to test the coil is by substituting it into a working bike (almost any single with a CDI).

Good question. Models such as these have pointed me in the right direction in the past and I always learn something from them. If somebody wants to correspond with me about it, message me.

I've been studying the effect the main jet has on part-throttle fueling and learning a lot. Have found an equation for two flow restrictions in series (in this case the main jet and the needle system) and have written a small spreadsheet based on the Dellorto PHBL 26. Is anyone interested in the results? I ask because presenting/explaining them would be a fair amount of effort. I'm also uncertain what the best way to actually present them would be (I know not everyone is as enamored with numbers as I am). Would anyone be interested in working with the spreadsheet? It's in OpenOffice Calc, but I could convert to MS Excel.

The problem is more than merely academic to me. My wife thinks the thing that will eventually cause her to stop competing is repeatedly starting the bike. I compete on a 250 because it's easier to kick.

Then I will defer to your experience in the matter, sir. Trials bikes are weird.

What is the original source of that chart?

I think the best way to make an alternator/starter work is in conjunction with an automatic compression release. But if just a compression release made your 300 as easy to kick as a 125, would you still want an electric starter? Yamaha used a small (3mm?) bleed hole above the exhaust port on the RD400 to make kickstarting easier. The hole really made no noticeable difference otherwise (as the guys who tried plugging them discovered). I investigated drilling a bleed hole in a trials cylinder once, but it would have gone right into the water jacket.

Tell that to the carburetor manufacturers. Here's just one example: http://www.sudco.com/jetting_assistance.html All are similar. I do agree with your statement in that if you install an extremely small main jet, the flow will be limited at part throttle. But for any reasonable size main jet for the application, that does not happen.

The main jet really has no effect until more than 3/4 throttle. Enriching the clip position may help somewhat, but the needle taper itself has more influence at 1/2+ throttle. Cleaning carbon from the head and piston would help if there is an accumulation. Have you tried a higher octane fuel?

I'm not saying it can't be done, but I do see hurdles to overcome. One is the very high static cranking pressure of a big-bore trials bike. The AT1 (and RD200) had small cylinders with low static cranking pressure. The snowmobile application has electronic exhaust valves that are undoubtedly in the high-rpm (low static compression) position during starting. Two is, on a trials bike, there is often little run-time between starts to recharge the battery, and may rule out a super capacitor altogether. As you may know, the GasGas Contact ES uses a conventional starter with a right-angle drive on the flywheel side. You can see KTM's version here: https://www.youtube.com/watch?v=KQTnUxj16nQ

Congratulation on solving the problem! (And thanks for reporting your findings.) I think the simple explanation is that the pickup coil is polarized. The leading edge of the trigger structure (whether a tooth or a hole) needed to generate a positive-going (or negative-going) pulse for the CDI to work properly. The trailing edge would then generate the opposite polarity. It's not uncommon for both of these events to be needed in order to set the timing and sequence of operations inside the CDI. Quite frankly, I'm surprised it made any sparks at all. There has been a lot of innovation in ignition system design over the years -- as much so as engine design, it's just less visible. It ain't called a "black box" for nothing!

I missed this the first time around. That delay is really weird. I guess if I had to throw money at the problem, I'd throw it at the CDI before the stator.

I fixed some typos. Did that make it any clearer?

I think you will find the exciter coil is the one just right of bottom center. That coil is physically small for the DC-DC converter approach. I still feel the voltage you are seeing from that winding is low, but cannot say for certain without reverse-engineering the entire system. It would at least be possible to rewind that coil by hand. You could further test the ignition coil by heating it and observing the resistance change in the secondary winding. You could also use your peak detector on the primary side of the ignition coil (but reverse polarity so the positive lead is grounded. The CDI capacitor discharges a negative-going pulse into the ignition coil.) It may be difficult to analyze those results, however. There's not much more testing you can do without an oscilloscope. Sorry I can't be more help.

Yes. I'm working on a lengthy write-up titled Improving 40mm Marzocchi Forks, but briefly... GasGas says to use an SAE 7.5 oil in their Marzocchi forks. Unfortunately, there is a lot of variability between manufacturers in what they consider to be a 7.5 weight oil. I strongly suggest that you select fork oil based on its kinematic viscosity (which is measured in centiStokes) instead of by its rated weight. Peter Verdone has a fabulous table of many readily available fork oils along with their kinematic viscosity. See: https://www.peterverdone.com/archive/lowspeed.htm Forks run cool, so all I care about is the kinematic viscosity at 40 degrees C. In the US, the recommended fluid is Golden Spectro Cartridge Fork Fluid 125/150 (which is 26.1 cSt @ 40C). Personally, I feel that is too heavy and am using Maxima 85/150 (which is 15.9 cSt @ 40C).

Those SKF seals are excellent. And, as faussy said, they should leak absolutely nothing. When you assemble them, a seal grease like Race Tech's "Ultra Slick" helps to reduce stiction. See: https://www.rockymountainatvmc.com/parts/race-tech-ultra-slick-seal-grease-p

I've always liked EBC pads in every motorsport application. They bed-in quickly, provide a good feel, and give reasonable service life. I once bought a set of Jitsie pads that were so hard as to be completely useless. Looks like Repsol and 300RR are different from standard 260. EBC'S FA644X is what you need (for 2016 model anyway, my catalog is from 2017).

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).