konrad

No. Idle jets are an M5 thread, main jets are M6. P.S. A rich mixture does not cause 4-stroking, but it can exacerbate it.

I'll add that trying the standard jetting is usually a good place to start with a stock bike. I don't think there's any shortcut to jetting. A lot of test-riding is needed to judge the changes. Jets are cheap, and having an assortment on hand is a big help. Some of it depends on the local fuel, and how picky you are. Luckily, with trials bikes it's usually pretty easy to get at the carb. I often use a 0.5mm shim under the jet needle clip to get things to my liking.

Change the ignition timing first (which will affect the perfect mixture strength). Retarding the ignition timing will make the engine more willing to rev. Make one change at a time to understand its affects. Hard to start from cold is likely the choke (enrichener) circuit. (But retarding the ignition timing may improve this.) You may be able to just flip the reeds over to make them seal. (My Shercos seem fairly tolerant to imperfect reeds.) Based on your statement regarding "running in" jets, I assume you are familiar with 2T MX bikes (which have an air screw for the mixture strength). Despite begin a 2T, the Dellorto has a fuel screw, which I find has a smaller effect on generally rich 2T engines than an air screw. Regarding feeling both rich and lean at the same time, it's possible the "transition hole" (engine side of carb from bore into idle circuit) is clogged. Make sure every passage inside the carb is scrupulously clean by spraying carb cleaner and compressed air thorough all the orifices. Don't be afraid to gently use a fine wire as well. I rarely make a jet change of more than 1 size at a time. The main jet only affects fueling from 3/4 to full throttle. Since you're using a slow throttle tube, this may not be much of an issue.

Swept, your encouraging words in my first post here meant a lot to me. You seemed quite willing to share your vast knowledge -- I'm sure your input will be greatly missed. Here's wishing you the best, and hoping you'll be back!

I just measured one at M6 x 0.75

The TXT 321 was my first trials bike. I spent considerable time getting the clutch to work to my liking (zero drag). Since this is your first motorcycle, you may not be too critical of that fault, but having the bike work properly will help prevent you from developing bad habits. A good trials habit is to have one finger (and only one finger) always on the clutch lever. Anyway, I made sure everything was perfect with my clutch components and it still would not disengage completely with the lever pulled to the bar. Eventually, with the clutch cover removed, I noticed that it was easy for me to rotate the pressure plate by hand when the clutch was disengaged. There was little drag and no tendency for it to rotate the engine. This gave me an idea. I rode the bike briefly with no oil in the gearbox. Guess what -- the clutch disengaged completely! I then refilled the gearbox 300cc short of the "correct" fill. This also produced nearly zero clutch drag. Although neither an owner's nor service manual seems to exist for this bike, internet sources say the correct gearbox fill is 650 - 750cc. There is a sight glass on the clutch housing that I had been using. I would guess it takes about 800cc to get the level in the middle of the sight glass. So when I fill 300cc short, I probably have about 1/2 liter in the gearbox. There is an advantage to having a lot of oil in the gearbox in that (short term) it can act as a heat sink and allow the clutch to work longer before overheating and slipping. As a new rider you probably will not be abusing the clutch to that extent anyway. Regarding Peterb's recommendation of using ATF, I agree completely. I tried every transmission fluid known to man in that 321 and nothing was any better than ATF, which is cheap and readily available. I use it on most 2T gearboxes now. I'll end with a story from Kevin Cameron about Kawasaki's KR250 road racer (circa 1975). The KR250 had a very tight gearcase, and when given its "correct" fill of 1,100cc of gear oil, it got so hot it burned the black paint right off the casting. Cutting the fill to 600cc made the situation tolerable, if not desirable.

There's some practical information in my EFI OSSA Notebook in the first post here. Some of it might be helpful.

It's fairly common for people to elongate the stator plate mounting holes to alter ignition timing. The amount of elongation I see there would only be a few degrees. That should not prevent it from starting. I would use epoxy for repair. Have no idea if JB Weld epoxy is available where your are, but I recommend it. https://www.jbweld.com/collections/epoxy-adhesives/products/j-b-weld-twin-tube Really, almost any epoxy would work -- preferable with a 24-hour curing time. I've even used Fiberglas resin on stator plates. HOWEVER... I think those stators are a know electrical failure item on the small Polini motors (a friend had an MX version with that trouble). I suggest talking to your Polini importer.

Everything I saw has a minimum threaded length of 28mm. So if you needed, say, 25mm unthreaded, you would buy a 55mm fastener and cut off most of the threads. This example is stainless, with a 70 ksi tensile strength: https://www.mcmaster.com/92095a299 That's soft enough that, I think, you could cut more threads with a die. But that's generally frowned upon. And using a spacer under the head would would circumvent what you are trying to achieve with the button head. How about some sort of slippery plastic covering over the original bolt head?

Not sure I understand your question. The key size is based on the diameter. The tightening torque is a function of several parameters (e.g., grade, diameter, pitch) but length really does not enter into it. Are you looking for a specific bolt?

My mistake, I'll blame my poor English skills. In the US, McMaster-Carr https://www.mcmaster.com/standard-rounded-head-screws has been a great reference source for as long as I can remember. They say "fully threaded" or "partially threaded" (which is far less common).

They're very common in the US, often called "button-head cap screw" or "socket button head".

In the aircraft world it's called the "grip". http://spenceraircraft.com/hardware/fasteners-screws-bolts/airframe-bolt.html

Don't get too upset, that paper was written in 1996 and is from the point of view of manufacturers, not consumers.

"Monolayer-HDPE tanks offer long-term structural integrity but will not meet future permeation requirements." https://www.tms.org/pubs/journals/jom/9607/alvarado-9607.html

The plastic should be abbreviated on the underside of the tank.

If it is electrical, you should be able to feel that while riding. It will feel like it's missing combustion cycles.

My first trials bike was a 321. Letting off the throttle will not produce "spark knock" (detonation). I'd be wiggling bearings. Sometimes you can isolate the source of the noise with one end of a hose (maybe 3/4 - 1" ID) held to your ear and probing the engine with the other end. And yes, one side of the kill button goes to the chassis ground.

Chris, you can determine the volume of ethanol in a fuel with a simple test: Fill a syringe with 90cc fuel and 10cc water. Shake it well, then let it stand for 10 minutes. If the "water" portion increases from 10cc to, say 20cc, that indicates your fuel is 10% ethanol (by volume). As for ethanol's effects on plastic, I'm sure it depends on the particular plastic. (I would advise searching academic/industry research papers for a credible answer.) My red plastic fuel jugs are HDPE (high-density polyethylene). P.S. There are many ways to improve octane rating. I would say, in general, the less costly the fuel, the greater the ethanol percentage.

There seems to be quite a few topics related to fuels on this forum. I'll add my contribution here. The content of both these write-ups was posted on other forums as far back as 10 years ago. My thinking has not changed. Ethanol Technical Perspective.pdf Leaded Gasoline Technical Perspective.pdf

The owner's name is visible on the number board in the video. A search lead me to this: http://www.evalbum.com/3036

Given the diversity of bikes presented, beauty really is in the eye of the beholder. I'm a big believer in the idea that "form follows function." "That" was worth googling: https://en.wikipedia.org/wiki/Black_Versace_dress_of_Elizabeth_Hurley

Mecatecno Dragonfly. Since I don't own the photos, I'll just post the link: https://www.mecatecno.biz/

Yes. I think that is a good idea. You probably should have an electrolytic filter capacitor on that line as well.

Ignition coils for CDIs are neither 6 volt nor 12 volt. CDI coils work on a completely different principle than "induction coils". The capacitor inside the CDI gets charged to on the order of 200 - 300 volts, and then is discharged into the ignition coil. Technically, such ignition coils are "pulse transformers". They typically have somewhere around a 1 : 100 (primary : secondary) turns ratio. Their primary resistance is very low (usually under 1 ohm). I just searched "CDI ignition coil" on eBay and found something for $8.25 USD shipped from China. Better yet: https://www.ebay.com/itm/IGNITION-COIL-YAMAHA-TTR125-TTR125L-TT-R125-TT-R125LE-2000-2009-2011-MOTORCYCLE/281087430819?hash=item41721dd0a3:g:iFIAAOSwDk5T1Lw~:sc:USPSFirstClass!55066!US!-1