konrad

There is another way to hold the flywheel, and that's by jamming soft aluminum between the primary gears (in fact there is even a tool made for this purpose): https://www.motionpro.com/product/08-0427 Of course, you would also need to remove the clutch housing.

Agree with above. If it were me, I'd clean/rebuild the old wheels. But then, being retired, my time is worth nothing. Lacing/truing wheels is not for the impatient. To be truly worthy of the moniker Caferacerman, it seems a necessary skill, no?

If you don't have a flywheel holding tool, you can use an "impact wrench" to remove/install the flywheel nut. These tools can be pneumatic or electric. See: http:// https://www.ingersollrandproducts.com/en-la/power-tools/products/impactools.html You will also need a "flywheel puller" with threads specific to your flywheel. I always lap the crank/flywheel taper with valve grinding compound to ensure optimal torque transmission. The Woodruff key is intended for location, not torque transmission.

I don't know anything about the TR80, specifically. How does the tank vent currently? At the risk of stating the obvious, drill and tap the fuel cap for a hose-barb fitting and install a vent with a one-way checkvalve like this: https://www.ebay.com/itm/MOOSE-RACING-ALUMINUM-VENT-CAP-FUEL-HOSE-SMALL-ONE-WAY-VALVE-COLORS-ANODIZED-MX/232728408990?hash=item362fb1b39e:m:m8S6mTDXwRrxYJaRgZoaXUQ:rk:1:pf:0 One caution, I've found some of the Chinese copies may look like the above, but don't actually contain a checkvalve.

It's great you reported back on your progress. (And very considerate of you to think about the next guy with a similar problem.) I'm assuming your ignition timing measurements relate to an arc at the perimeter of the stator plate (which is obviously a relative measurement). I hope this does not come off as "preachy", but a more meaningful way is to specify an absolute measurement in degrees BTDC with a timing light, or mm BTDC with a dial indicator against the crown of the piston. But, ultimately, it does not matter because trials is all about feel. So, I would encourage you to experiment with other ignition timings so long as you have some way to reference each one and are able to return to it.

With the username "Sine", I'm guessing it will be an AC motor?

Your assessment regarding stuffing is correct. I don't know if it was OE or not, but "modern" 2T trials bikes use high primary compression ratios. This yields a lot of torque at low engine speeds at the expense of greater pumping losses. The exhaust systems are usually quite simple and don't benefit from a large crankcase volume. The holes are for balance factor, so if they are plugged, it's with a low-density material. Often, a sheet metal cover (think automotive frost plug) is pressed into place. I have seen cork epoxied into place as well. The fact that it's still there says the material has decent longevity.

Below is a graph from SAE paper 790429 that shows exactly that. Although, somehow, they labeled the units of Reid Vapor Pressure in pounds instead of psi. But this does not seem to cause much of a problem if the system is sealed. For example, I leave E10 in my chainsaw (in a cool garage) all winter without ill effects. I also over-winter gallons of E10 in a sealed plastic container for use in a 4T backup generator. You would think that if all the light ends had gotten out, it would affect cold starting, but I really don't notice anything. BTW, I read your clutch fix a long time ago (a friend showed it to me when she was having trouble with a Beta clutch). The format gave me the idea to make .pdf files for use on message boards. So, thanks for that! Here is a link to my thoughts on ethanol (and lead) in gasoline.

Our "natural" gas is mostly methane. It's also called CNG (compressed natural gas) and LNG (liquefied natural gas) depending on how it's stored/transported. Propane is also know as LP (liquefied petroleum) gas. +1 for Cat Stevens.

This is good advice! I suggest putting everything back together, and setting the TPS to about 0.6 volts as measured between the TPS center pin (wiper) and chassis ground. If the bike still runs poorly move the TPS slightly. Don't move it randomly. Move it in increments of about 0.02 volts. Try both increasing and decreasing. It is possibly your injector is dirty and leaking into the engine. Some automotive repair shops can clean injectors. But, you really must have the diagnostic system. Here's how to build the interface cable: https://www.trialscentral.com/forums/topic/69670-building-an-ossa-ecu-diagnostic-cable/ Others on this forum have offered the software. A lot of reading on this forum will help.

Yes, you have the original fuel injector. I paid about $20 USD for one via Aliexpress.com There are many choices: https://www.aliexpress.com/wholesale?catId=0andinitiative_id=SB_20190224120228andSearchText=FBYCG80 Also, lots of information in my OSSA EFI Notebook that could help you: https://www.trialscentral.com/forums/topic/69622-efi-ossa-notebook-formerly-tr280i-wiring-diagram-annotated-in-english/

I found plenty in the US on eBay by searching "Mahle KL97" . As I recall, peterb mentioned the same filter is used in the OSSA (but is much less convenient to replace).

My first trials bike was a TXT 321. It took 8+ kicks to start from dead cold. As I'm sure you know, the enrichener (choke) jet is replaceable in the Dellorto. Mine came with a #60 (0.023" orifice). I drilled mine to a #70 (0.028") and it started much better from cold.

Poor scavenging.

Perhaps too late to help you but for future reference, operation of the "vacuum" or "pulse" type fuel pump is describe here: www.walbro.com/wp-content/uploads/2015/12/FPC-pump-8-20-12.pdf

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?