lemur

Running is good 👍 race fuel has a better shelf life if you're going to leave it stand for ages. Fuel filters are super expensive because they want to sell it with a fuel pump included.

Absolutely the idle needs to be set correct and you can't touch the throttle when you kick it over 👍

The engine still runs and doesn't sound like it has a bad main bearing? It would need to be the right hand side because the alternator side contains engine oil. ... I'd be tempted to change the fluids, ride it and see if the engine oil level increases, if not then that's not where it's going.

Super easy to check your fuel pressure and rule that out. Two methods are covered in the service manual, one that requires a gauge and one that requires no special tools. Set your valve clearances, don't just look at them to be close, physically set them precisely as you can. (You need to drop the engine part way to do it and you need a micrometer handy to test your feeler gauges and get a feel for the correct clearance.) Owned 3 4RT's at the same time, one did not start when I was about to begin a competition and I had to use my back-up ride. After that I took parts from the other bikes and swapped absolutely everything physically possible with no joy. Once I determined it was nothing fuel or spark related I set the valves very carefully and precisely as possible and it worked perfect since. Same problem eventually happened with three 4RT's out of the five that I've owned since 2005.

On the last oil change when there was barely any transmission oil at all, was the engine oil level overly high?

Is that the brake with a Brembo symbol on it? You use air? Air compresses, fluid does not. I always just use the hydraulics that are already attached to remove the calliper pistons. Hold back the piston that moves easy with a pair of pliers and the other piston will slowly hydraulic out.

Step one, obtain a service manual, step two test everything the manual tells you to check or inspect, step three tell us what your findings are and we can probably help you interpret the results. Probably best if you start a new thread unless you know for a fact that you have "over-voltage issues". If it is indeed an electric problem that only manifests when hot, I would start with inspection of the alternator coil and see if it looks like burnt toast, or if the coils internal resistance is correct. Electric issues are always best to troubleshoot starting at the source of power and working down stream.

When you have a small volume of oil that has no filtration or water separator, the logical best practice would be to change the oil out frequently. The transmission oil I have been using successfully for decades in dozens of different engines costs about 5 bucks to change and it works great in winter or summer. Suit yourself but no transmission oil that should be changed frequently is worth 24$ per litre, you're paying outrageous money for packaging. If you want to know what is in a packaged chemical product the best place to start is the MSDS (Material Safety Data Sheet) it's the only place they are compelled to be 100% truthful about what they are selling you.

I just checked the price of the transmission oil you are using compared to what I use, says you pay about $24 per litre and I pay $8.10 per litre. That's sick. What's the nearest farm tractor dealer to you? Buy what they run in the hydraulics and transmissions of their big expensive equipment, change it frequently, it will work. ... do not over-fill, that won't work.

Is it still dragging in first gear only and no clutch dragging in second or third gear?

Without even getting to see it, if the damage is limited to the copper then it is serviceable, if it went deeper that's not so good.

Quote from the TRS Owner Manual (same for all displacement models) "This motorcycle uses two-stroke synthetic oil mixed with 1% 98 octane fuel. Do not use any other kind of lubrication without previously checking with an authorised TRS mechanic." Recommending a synthetic oil labeled 100:1 pre mix ratio is not over thinking, that's just reading and applying the instructions correctly.

It's not terrain that will cause your combustion chamber temperatures to be wrong or even engine revs, it's the actual fuel to air ratio. More oxygen = hotter burning so if you run too lean in any range of operation you will see more heat, right up until there is not enough fuel mixed with air to ignite and then you will have fuel residue. If the manual calls for 100:1 oil to fuel and you run 60:1 how much excess oil are you putting through your engine? Something in the range of 40% more oil than the engine can burn.

" thinking maybe the varnish hardened up when the bike cooled and stuck the rings to the barrel?" The rings jam up in the piston grooves and then the ring no longer follows the shape of the barrel. That creates a gap between the ring and the barrel where raw fuel and raw oil burns and contributes to more carbon buildup. Carbon is black and that mixes with non-combusted oil to make a glue like residue. A piston and its ring pack needs to operate as an assembly where gasses from compression push the ring more tightly against the cylinder barrel. Look at how a Dykes piston ring works for a better explanation.

" The oil mixing ratio needs to be adjusted slightly 130 ml 2-stroke oil on 13 liters of petrol is a mixing ratio that still functions well in practice. However, with a higher proportion of substantial taxation, this may be too little and this really depends on the degree of taxation." They are confirming you should run 100:1 ratio same as your service manual says. ... for what it's worth I run my TRS 300RR at 100:1 like the manual calls for and it hasn't seized up yet with more hours then you have on yours. That crap about higher taxation is to cover their butt, in the event of a failure they want it to be your failure. Lots of producers have taken to not even suggesting an oil mix ratio on their packaging, so if in doubt buy one that states it can be run at 100:1 on their documentation or packaging. That's what Amsoil says right on their plastic bottle "100:1 pre mix"

Only in the amount of throttle twist he will need to go up the same things he goes up now. All are extremely capable machines with larger displacement models demanding finer throttle and clutch control.

No torque converter in a standard transmission and automatic transmissions use bands not rubberized cork friction plates. Excavator and farm tractor on the other hand has everything including the rubberized cork friction plates for brakes. If you owned an excavator the service manual would indicate that ATF could be used in substitution to the recommended hydraulic oil with the note that "Hydraulic fluids have a higher operating temperature range and maintain viscosity better than ATF in a broader temperature range. " Glad you found it funny. ISO 46 hydraulic has a viscosity of SAE 20 and the recommended was SAE 10W-30 they virtually have the same viscosity.

I just googled that oil, it's strawberry scented 🙄 why would anybody ever intentionally put something like that into an engine is beyond me. Not much doubt you should change oil brands. What does your exhaust packing look like, is that all gummed up with strawberry stuff too? What fuel are you using? I run 50% premium pump gas and 50% Sunoco GT260 race with Amsoil Sabre 100:1 being my preferred oil. Some brands I have tried in the past gummed up the exhaust packing real bad.

Yikes that is not a pretty sight. The only time I had a 2-stroke look like that and have rings jam was in a chainsaw that I was using old 2-stroke oil that was so old I should have discarded it. I had to remove the piston and clean behind the rings, no way you could free up the rings proper without removing the piston.

If my clutch sticks, drags or makes noise then I know there is water in the transmission fluid which in my case is ISO 46 hydraulic oil. It means time to change it. SAE 10-30 is a multi-grade engine oil and transmissions don't need multi-grade oil, transmission oil is never subjected to combustion chamber temperatures, all it lubricates is spur gears, shift forks and a wet clutch. If your engine is left standing for a long period without use and there is any water from condensation or fuel in contact with the clutch then your friction plates will swell. That is what causes the stick and drag. Take all the friction plates out, clean them well and dry them completely before reassembly with fresh oil. Examine the dry plates for consistent thickness in the friction material, sand them flat and even if necessary or replaced damaged plates as required. ATF is Automatic Transmission Fluid and perfect if your motorcycle had an auto transmission with a torque converter and everything is virtually fluid driven. Trials bikes have no auto transmission, no torque converters, what they do have is the same things inside as a farm tractor or heavy construction equipment like an excavator. Hydraulic fluids have a higher operating temperature range and maintain viscosity better than ATF in a broader temperature range. If the small gaps between the clutch friction pads becomes clogged with dirty oil and burnt pad material, then fluid can not escape from inside the clutch pack causing the clutch to slip. Lot of people miss that one.

I have a 36 tooth rear sprocket that came free with one of my 260 4RT' and I rode that sprocket last winter to see if it was any better. It required I use second gear more because it won't pull third strong enough from a dead stop. Nothing wrong with aluminum rear sprockets if you keep your chain good. Running a stretched chain is what kills the sprocket. With standard gearing third gear is best for faster trails and it pulls strong in fourth, with faster gearing you'll typically end up riding in one gear range lower then you do now. ... I'm going back to standard gearing for this winter, gearing it faster had no practical advantage.

Might be OK if you are building an electric powered motorcycle.

For pre-mix 2-stroke oil it depends on what is available locally. I use to like MC-1 from Belray back in the day because it was the first you could mix 80:1 in a Montesa 360VA remember back in the day gasoline had much higher octane, old bikes were designed to run on period fuels, personally if I was running an old bone bike today it would be on boosted fuel and synthetic mixed as per the manufacturers label. Some brands tend to plug exhaust systems worse then others. For old Bultaco transmission and clutch you are good using all season hydraulic excavator oil ISO 46 which you can buy in quantity from any farm or heavy equipment store, I have used lots of brands and they all perform equally well. New Holland Ambra, Kubota, John Deere, Hyundai It's basically the same thing they use in farm tractor transmissions. Inexpensive enough to can replace it frequently. Farm tractors have everything inside them same a 2-stroke transmission, gears and wet clutch/brakes.

@dunk10 I found a service manual, no oxygen sensor. I recommend you do a fuel pressure test, the Sherco manual shows that you need a pressure gauge to do that and you are looking for 3 bar which is equal to 43.5 psi If you don't have a pressure gauge I know you can also test fuel pumps by measuring the fuel volume output. For example a Montesa fuel pump which operates at similar pressures (33 to 46 psi), when connected to a 12 volt battery the pump will move 0.749 l/min (125 cm3 / 10 seconds)

Do you have a service manual? You described lean operating conditions and the bike is fuel injected. I assume the air filter is clean and correctly oiled with no obstructions, no mouse nest in the air intake. Next suspect would be sensors, starting with an oxygen sensor assuming it has one. Check your fuel pressure because low fuel pressure could be a cause, check the fuel filter itself for damage and all the hoses attached to the filter for splits or leaks. The injector could be the source of the problem, but I would check all those other things first.