lemur

Dump the old oil into a clear glass container and you might even see all the problems before venturing inside, watch for water, bits of slide bushings and the amount of grey aluminum discolouration in the oil which came from wear in your lower fork leg.

Ask the TRS dealers in B.C. I already had a TRS battery pack exchange serviced by the dealer out your way.

Surflex plates will look like normal organic clutch plates, I really wonder if he has a mismatch of parts now, I can't imagine the original plates have cross hatch spaces like that. Are we even looking at carbon fibre discs and is that why they are so black? Cork or paper discs should clean up to be cork colour like in the pictures of new ones and nothing in a 2-stroke transmission should make the oil and pads stain black unless it is from burning.

My rule of thumb is: Light oil yields lively suspension, heavy oil retards suspension, do I want my suspension to act lively or retarded. It's the springs that carry the weight, if you need to carry more weight you adjust the spring rate.

Found this: The steel ring in the photo with printing on it appears to be a spacer to make the clutch pack thicker and the fibre plates are not black they are the colour of organic friction plates. These look a lot like your clutch, if your clutch pack is undersized it could be you are missing that spacer. Oil should never be as black as those plates or the oil has been burning in there for a while. Personally for the cost involved I would replace the clutch pack with stock parts and be done with it. add: There are only 3 friction plates in this set because it is for a newer model GasGas, so no I am not suggesting this is the right part for your bike, I am suggesting a previous owner exchanged the originals with something that apparently does not work.

Not sure what the original clutch plates on your bike look like, but the plates in the photos look like S3 aftermarket plates. Thickness of the clutch pack should be taken from the service manual. The transmission oil I use in all my bikes is the same oil they use in a farm tractor or excavator so it is relatively inexpensive and very easy available from any heavy equipment store. The oil will be called UDT (Universal Drive Train) or all season hydraulic excavator oil and is well suited to wet clutch and wet brake applications. The brand I am currently using is sold by Kubota but I have used similar spec oils from other manufacturers with equal success. Oil level should be no higher then the plug where a sight level window would be if so equipped, just like the Jim Snell video they linked you in your other thread.

If the spaces between the friction pads become clogged with friction pad material or if the oil level is way too high oil pressure can happen that pushes against the springs. It is one of the scenarios that can make a motorcycle clutch slip. Yes to the groves needing to be clear so that oil can pass through, some times it is very obvious on inspection where the groves have become plugged with fibre material.

Imagine if you could build something that held all the little round cells in stacks so you could replace just one bad one at a time, sort of like in a 100 year old flashlight. I bet they make them like that some day.

I was not questioning the friction pads being intact, the other guy was, it's the spaces between the pads I had question with and I asked if the clutch pack looked swamped. If oil can not evacuate from inside the clutch pack then hydraulic action can keep the clutch from engaging.

Can't tell from here but if the clutch basket is swamped the oil level is too high. Another thing to inspect and clean is the spaces between the clutch pad friction pads, if oil can not evacuate from inside the clutch pack then hydraulic action can keep the clutch from engaging.

Have to ask because you didn't specify; any chance you over-filled the transmission oil capacity?

Then call it a rotor. We know it has one of those because yours has a crack in it and if you search for 'KTM 50SX rotor' you come up with something that looks very similar to your broken part.

Unlikely but to know for sure you would need another same model bike that is working.

I'd pull it off to determine exactly why it split, see if the crack can be reduced back to zero and hit all the cracks with superglue to reinstall and see if it splits open again.

Owned 5 4RT models from 2005 to 2017, 250, 260 and 300RR, owned 3 at the same time and swapped parts between each to trouble-shoot. Model makes almost no difference because the 4RT didn't change much to the point where most parts from one will fit right onto the next and work just dandy. I have the header pipe with the Cat converter and the O2 sensor from my 2014 260 4RT sitting in my spare parts box. That was my only 4RT that came in the crate straight from Spain unopened.

You're right, sometimes it's better to direct the question to the source of an answer and let the reader figure it out from there 👍 https://www.nature.com/articles/s41598-023-43695-6

When I installed the race kit on mine and removed all the street stuff the only thing I had to alter was the idle screw after letting it come up to operating temperature. It came with the catalytic header plus the straight header plus heat shields for both, ECU seemed to know how to deal with either way or with restrictors in or removed. PGM-Fi works brilliantly, only way I could make one run rich was if the air filter was plugged.

Did your bike come in a crate straight from the factory or was it unpacked by a reseller? On my 2014 4RT the race kit parts and the supplementary instructions came included with the homologated bike in the crate. Lots of extra parts for the dealers to scoop prior to resale. The bike was initially fitted with all of the restrictors required to make it street legal for a beginner limited license and all of the race parts were in boxes. An expensive ECU was not included at that time but likely the purchased one can be user programmed beyond the 2 position switch presets, & not something the average rider will ever need.

Manual for the 2020 ST250 shows a drain hole plus an inspection or fill plug they tell you to remove to drain the oil. Odds are the plug is at the same height an oil level window would be if it had one. First check would be to measure the quality of oil you drain out and go with roughly the same volume and then see where that fills to relative to the inspection/fill plug hole. Search for "Oil comparative viscosity chart" and you will find a chart that details the relationship between ISO, AGMA, SAE auto and SAE Gear oil viscosity. Personally I use ISO 46 hydraulic oil in all my 2T and 4T wet clutch/transmissions and never have a problem, same oil they recommend for all season excavator and farm tractor applications which use virtually the same type of gears, seals, shift forks and friction plates. ISO 46 viscosity equates to AGMA 1, SAE 20W auto oil, or SAE 75W gear oil. ISO 46 can be purchased from any heavy equipment store in quantity and costs about half the price or less, so you can change it out twice as often. Too much oil in the case can cause clutch slippage problems and robs power, the oil level is relative to the clutch basket, the clutch should never be completely submerged or the plates will not compress because of hydraulic pressure on the inside of the clutch plate friction pack. Your transmission and clutch do not require a multigrade engine oil which is formulated to accommodate cold startups and a much hotter internal operating temperatures.

It's a permanent magnet is it not? There are a lot of iron filings stuck to the magnet in the photo, that might cause shorts and indicates a wear problem, I would clean it all up, test the coils and try again.

The 4RT is a superior all around trail bike, they have a broad powerband, start easy, cheaper on fuel, tough to break and hold resale value better than most. Easier to ride at non-competitive level trail riding, if you can still ride a motorcycle I would think 4RT is the one. I ride TRS now but would go back to Montesa 4RT in a heartbeat if sales and parts dealerships still existed where I reside, I rode 4RT' for 16 years. Montesa/Honda fuel injection makes the 4RT far superior to other 4-stroke trials bike models imo it would be the only 4-stroke trials bike to consider. As for servicing the 4RT, you will need to be able to adjust valve clearances accurately after 4 or 5 years of riding and it becomes harder to start, otherwise they are not much different compared to a 2-stroke to service. Replacement spark plugs are way more expensive but you will rarely need to replace one. Air filter is way better compared to some and the plastics are expensive but durable. 4RT works great in winter as long as you don't let the oil get thick in sub zero temps, sub freezing temps makes it near impossible to start unless you build a fire under it. 4RT Header pipe runs very hot and needs a shield upgrade or you will melt your riding pants on it regularly.

"Stator looks OK, noting obvious." Are you testing the stator coils with test equipment or by eye 🤔 looking at coils tells you nothing unless they are burnt to a crisp, you can meter test coils for resistance or you can oscilloscope test the AC output and confirm it is fully functional. Sparkplug cap and wire has been changed? They don't last forever. "Plug is gapped ok, looks ok, not fouled. " Sometimes the insulation is cracked and the defective plugs will spark way up inside the plug body and not at the electrode gap. Try another new plug. If you can't narrow it down to being either a carburetor or ignition issue there is not much anyone here can help you with. Do you have access to another GasGas TXT you can swap parts with, that is what a dealer would do to eliminate the carburetor as being your problem. Parts swap is also the only way you can reasonably test the ignition module.

Holy that looks expensive, I hope I can own one 😎

You act like a thermostat switch is a totally non-required 20$ part that every manufacturer puts on their machines without reason. What's the big deal with just fixing it! If he leaves the fan run 100% and fries a 90$ rectifier he can thank you for the recommendation to ignore it.

Wait a minute, so if you never had a thermostat switch fail either 🤔 the only thing self induced is if he doesn't fix it after he bought a broken bike.