thats_a_five

4rt exhaust/silencer cover If you have a spark arrestor or screen baffle in the end of your exhaust system, check to see if it is clogged with soot or oil. That will cause the same sort of symptoms you are describing. A good cleaning will cure it if clogged.

Here are some thoughts and suggestions to try before you spend money throwing parts at it. I know from your posts that you have been riding along time and are pretty knowledgeable about bikes. So, I offer my thoughts in hopes they will trigger you to consider something you already know but maybe skipped over in your diagnosis. Has the bike always done this? If not, then consider what has changed? In your case it sounds like several things have changed in an attempt to eliminate the problem. There are 2 main potential types of issues that could be the cause: 1) Mechanical 2) Hydraulic. Mechanical Something is binding or forcing the pads apart differently sometimes. Your efforts to drill the hotel and open the holes in the pads should take care of the binding. Did you check for grooves or steps worn into the caliper? I usually will put a very small amount of anti-seize on the sliding surface of the pads and pins. Is the rotor bent? That would wobble and push the pads apart, making for more travel needed to contact the pads. Test with the bike on the stand, front wheel up. Hold a pencil or marker close to the rotor on something solid like a jack stand. Spin the wheel and look at the gap between the rotor and pencil tip. It should be pretty consistent as it spins. Worn wheel bearings would cause the same sort of wobble. Loose axle bolt could also allow this. Test with bike on stand, brakes off, grab the wheel top and bottom, try to push the top left while pulling the bottom right and repeat. If you feel any looseness or clicking the bearings or axle are probably the culprit. Lever and perch. Check for wear in the holes. Out of round holes can cause inconsistent movement. Lube them. Hydraulic You changed the caliper seals and pistons. Did they move smoothly in the bores? Was there any corrosion or pitting? Is the lever consistently firm or is it mushy sometimes? If it’s mushy, there is still some air in the system. Bleeding these things can be challenging. One trick is to park the bike with the master cylinder being the highest part of the hydraulic system (Bike on the stand, front wheel high, bars full lock left). Apply the front brake and clamp the lever to the bars with a bungie cord to hold brake pressure overnight. This will force any bubble to the top of the master cylinder bore. In the morning, take the cover off and watch as you release the lever. If there was air, you will see it escape through the return port. Speaking of the return port, you know that when the lever is pulled, the spool inside the master cylinder blocks the return port so the pressure is transferred to the wheel cylinder applying the brakes. When the lever is released, the return port is uncovered to allow the pressure and fluid to flow back into the master cylinder reservoir. If this port is not open, the pressure holds and the brake pads can’t move back from the rotor. The hole could be blocked by some crud or the spool might not be returning fully when the lever is released. With the cover off the M/C, squeeze the brake lever, then release it. You should see a miniature geyser of brake fluid. If it is blocked with crud you can use a thin wire to clear the hole (this is best done with the spool removed otherwise you are pushing crud further into your brake system). If the hole is still covered by the spool, it is not retracting full. This could be caused by Foreign material between the end of the spool and that little C-clip, or because there is not enough free play in the lever adjustment. Floating disc. If you still want to try a floating disc, you can simulate that by putting some small o-rings on the bolts each side of the disc but not tightening them too much. This would allow the o-rings to squish, so the rotor can move a little. I would suggest using some sort of removable thread lock so the bolts don’t unscrew while riding. Keep us posted on what you find.

Oni Nou is correct about ensuring a ”Trials Bend.” A clarification on another point. Traditionally, motorcycle bars are at 7/8” diameter for their entire length of the bars. In recent years, companies have made “Fat Bars” that are 7/8” at both ends to be useable with existing lever perches and throttle tube, but they taper top fatter diameter at the point where they mount to the triple clamps. I am not sure, but I think the fat section is 1 1/8” diameter. I have never had fat bars so can’t make any personal comments. People have said that they significantly reduce the shock to the arms, reducing fatigue and arm pump. So, check your current bars. If they are the same diameter, end to end you have a choice. Buy a new set with same bend and diameter, or upgrade the clamps on the upper triple clamp to fit the “Fat Bars.” If the bike already has the “Fat Bar” clamps you need to replace with new “Fat bars” or you need to change the clamps to the smaller diameter bars. But before you go changing bars. How tall are you? Stock bars generally work OK for people from 5’ 4”to 6’. If you are taller or shorter, you might want a different “rise”. Most people find the standard trials riding position is with your shoulders lower and the butt more “out” than other bike riding. Also, most trials bars are aluminum. Some time with a “scotch-brite pad or emery cloth will put a nice “brushed” finish on the bars with little effort. You could even go to a “chrome like” finish with proper polishing compound and wheels. While you have the bars off, inspect them carefully for any cracking by the clamps.

I am not an expert on your bike but the fans usually don't come on when the bike first starts. The fan comes on when the water temperature get high enough to turn on the thermo switch. It should turn on and off as needed while you are riding.

You already know the fan works direct from a 12 volt power source so there are really only 3 other possible faults: 1) bad thermo switch. 2) bad stator (unlikely on that bike) 3) Bad electrical connection or ground. Generally the fan will come on and off while riding, even easy riding. What some people call the thermostat in the radiator is actually a thermo switch that turns the electric power to the fan motor on and off. I would start by simply unplugging the wires from the thermo switch and jumper the wires in the harness together then start the bike. The fan should come on immediately when the bike starts. If it does, you know the stator, and wiring are OK and the switch is bad. Remove the jumper and the fan will not run even with the bike running. Don’t worry, you are only talking 12 volts and low amps so no risk of serious shock. The proper way to test that switch is to remove it from the bike, connect to an ohmmeter or battery and light bulb, then put the switch in water. Cool water the switch should be open (off). Heat the water and the switch should click on when the water gets close to boiling.

When I first got my '05 4RT I felt it was too fast like yours. I went to a 9 tooth front sprocket (43 rear) and it was a lot better. I also set my idle at 1900 because it was much less likely to stall when I lugged it too slow. As my skill improved I was able to do full lot turns at idle with or without using the clutch. When it was time for a new chain and sprockets I went with a 10:44 set-up (Thanks to Mike at the Tryals Shop in NY for that recommendation) that is perfect for me. Have fun!

A buddy uses the technique described by D2W and usually rocks it front to back 2-3 times to get a good prime in the cylinder then it lights first kick. With practice you will learn how many rocking motions your bike likes. When you do kick,make sure to get the kick lever at the top of it's stroke, then push slowly to get any slack out of the gears, then a quick SNAP of a kick. Seriously, if you don't take the slack out first, you will be replacing the gear segment and/or the clutch basket when the teeth snap off.

Trials motors don't need the frequent top ends like MX'ers. Many trials bikes go for hundreds of hours without rebuilds. They are so lightly stressed compared to bikes that are constantly on the rev limiter. Those TXT's are almost bulletproof in that regard. Do keep your eye on the tranny fluid. The water pump seals have a tendency to go out, resulting in milky oil. There are kits with the seal and a new shaft because they get grooved. Keep good grease in your linkage (dogbone) bearings and always carry a spare plug. If you do any long uphills, expect the accumulated oil in the exhaust to smoke quite a bit. Its normal. Lots of good videos on Youtube. Watch them on slow speed to be able to see the techniques more easily.

Most people run about 80:1 fuel:oil ratio. Reducing the oil will result in a richer mixture so you may need to adjust your idle screw a little.

The brake rotors are “floating” type which means they can move some, but they should not rattle. Pop off a couple screws (or all if you want) and put a dab of silicone glue on the tabs, then reinstall the screws. The squeaking can usually be eliminated with a little deglazing of the rotor and pads with some 280-220 emery cloth. New pads are pretty inexpensive if they are badly worn or too thin. Bleed the brakes well with new fluid. Rebuild kits for the master cylinder are also pretty inexpensive. I thought my brakes were OK but after rebuilding and bleeding I was pleasantly surprised at how much better they worked. Compare the size of the rotor on your KTM to the Gassers. Probably a lot bigger diameter on the KTM. You don’t need massive braking on a trials bike, you need to learn proper body position and techniques. Watch some good riders who can hop their rear wheel when completely stopped. That is not about brakes, that is technique. Enjoy your bikes.

Keep your eye on the transmission fluid. It will get milky when the coolant leaks past that worn shaft. And it will. Replacement shaft and seal are available as a set at a reasonable cost. Remember that the oil lubricatesall the gears, bearings and clutch parts. Water and coolant are poor lubricants.

I have had a similar sounding problem with my 2005, related to the air filter. Particularly if I use the spray on air filter oil, it pops and stumbles under load. I put in a new filter lubed with motor oil and problem solved. Spray oil went into the bin. I hope this helps.

You say “they said there was a white sludge in the M/C - looked like it was mixed with water.” If they did a thorough flush the problem should not repeat. For water to get back into the system it would have to get past a seal somehow. Do you ride through deep water? If there is a bad seal or loose fitting on the slave cylinder, water could be drawn back into the system when you let off the pressure on the lever. Are you using a pressure washer to clean the bike? They can force water past oil seals on the slave or the master cylinder.

Filling with oil would prevent internal rusting - if all the holes and welds are oil tight. It would add some un-sprung weight. Just remember that the oil is in there if you ever decide to remove the side stand bracket.

WD40 is primarily a solvent with some light oil. This is not a very good, long term solution to the rusting. A better solution is to get some of the product designed to convert the rust to iron phosphate. This seals the surface and prevents further rusting. You would need to remove the swing arm from the bike, seal a couple holes with duct tape and pour in about a cup of solution, tape the fill hole then turn it over and over to fully coat the inside surfaces, remove the tape, drain out any excess and let it drain and dry for a couple days. There are several companies that make such a product. I have no connection with any of them. My local hardware store sells a product called Krud Kutter Rustex-Rust Converter. I have had good success using this product.

From what I understand, the device will communicate with any mobile phone that has the related app installed and in range. So, if the crook has the app, they could lead the police right to themselves. Even if they don’t have the app, if they drive past others who do have the app, the crooks will leave a series of electronic ”breadcrumbs” as they travel. Of course the usefulness of this is directly related to how many people have the app on their phones.

I see these GPS tracker devices (TrackR, Tile) advertised that work with mobile phones and GPS technology. They run on a small, replaceable, battery that probably last a year or so. It seems like it might be a good system that could be mounted on a bike in a hard-to-see location. Reportedly they will communicate using Bluetooth with any phones with the app loaded, and communicate their location to the owner of the device. This information could then be communicated to police to help recover the bike. Has anyone tried such a device? I have no connection with either of these products or companies.

I have heard rumors that sometimes those queue jumpers have had their fuel tap turned off, or their idle screw adjusted, or their spark plug wire mysteriously come loose at a latter section. Of course they are in such a rush that they don’t become aware until their bike stalls half way through the section. Karma.

Giving the idle jet a little more gas with the screw or move the clip on the needle one step might help.

It would help if you edited your profile to show where in the world you are located. With a username of SherpaTenzing, I think you might be in Nepal?

I am not an expert on those calipers but is sounds like there is still some air in the system. Brakes on trials bikes are notoriously hard to bleed completely. Many people back bleed with a big syringe. I finally bought a vacuum bleeder ($20 at Harbor Freight) and it works awesome. Discoloration indicates they have been hot as you probably know. Unless it is extreme, it is not a big problem. You can remove a lot of it with some 150 - 200 grit emery cloth and get back to a shiny metal surface. If you are still not satisfied, here is an old trick. Ride a couple hundred feet with light pressure on the brakes. Get them hot but not glowing. Immediately spray them with the garden hose. Do this 2 - 3 times. I don't know why this works, I know it does. Good Luck. I see you are in Oregon. There is a great club in the Portland area. Columbia Observed Trials Assoc. (COTA).

A couple thoughts: Those jet sizes sound a little big for a 125 but it should still run. I run a 40 and 105 on my 200cc Honda with stock intake and exhaust. On some carbs, the “fuel screw” is actually an “air screw” so it works opposite of what you might expect. DelOrto’s come to mind. Not sure about your carb. If your “Idle (speed) screw” is all the way out, the slide is probably too low, completely closing off the air supply to the motor. For an engine to run, you need spark, fuel and air. With the needle all the way up, there is maximum gas getting to the motor. After trying to start it, is the spark plug wet with gas? It sounds to me like the engine is getting flooded with fuel.

Hey Mark, Great ride on Sunday. Maybe this will help with your RTL carb. I had a similar acting slide on one of my old Honda’s. On close inspection I saw that the index pin had worn and galled up the groove in the slide. Some very careful work with a set of jeweler’s files smoothed up both the pin and the groove in the slide. I followed that up with some polishing compound (toothpaste) on the slide and moved the slide up and down with my finger until it was polished. A good cleaning and it works better than new.

It sounds like the engine is getting a lean mixture. Check to see if the fuel tank is venting correctly. A simple test is when it starts to rev up is to loosen the fuel cap. If it slows down, the vent is plugged.

I had the same problem with my TY250A. Did all the things as above with the same result you had. I finally tracked it down to the lever actually bottoming against the throttle tube and grip. With the lever removed from the bike and in a vice, I heated up and bent the lever to be farther from the bar. I got a little extreme because I wanted to be able to use 2 fingers on the brake and have have the lever come out before the other 2 fingers. It looks strange but works great. On any surface, other than paved, I can lock the front wheel.