2017 txt gearbox noise

[SamAs]

Hi all, Ive recently got a 2017 txt racing 300 and it’s making a noise in the gearbox. There is a ticking noise that im assuming is the chain as it does this in time with the master link. But once I shift into 4th gear the box starts to whine like crazy. I know theyre straight cut gears but it sounds like a race car, it’s almost louder than the engine. I’ve been told that it’s a case of possibly bearings or something in the box but seen on an older post on here that the whine is “somewhat normal”

im just trying to figure out if I need to take the engine out or not as I’ve never done it before and dont want to do it if I don’t have to. But I want to do as much as I can myself to save money as the bike cost me a lot. 
 

thanks in advance for any help, I might end up taking it out soon anyway it’s just a bit daunting 

[RonH]

SamAs, I don’t think I’ll be much help to you but I have a 23 TXT 250 that does NOT whine when shifting to 4th. I think the engines are nearly the same as the 2017 but I could be wrong. I’m no mechanic and there are others on here that will have better judgement than I, but I simply wanted to let you know that in my experience, on my bike, there is no whine shifting to 4th. If there was I would be worried. So far, working on my own bike, I’ve found it’s simpler than I ever imagined to do it myself. If you’re mechanically inclined and have common sense, I’d say go for it on your own. Just review and follow what you find in the maintenance manual if you have it. I’m all about saving cash too. Good luck!

you can download the 2018 manual for free here: https://drive.google.com/drive/folders/1xOzbrZQDO_W_AxpjvHU1xJMOqfRsVfPJ

Edited Monday at 06:19 AM by RonH

[konrad]

4 hours ago, RonH said:

...you can download the 2018 manual for free here: https://drive.google.com/drive/folders/1xOzbrZQDO_W_AxpjvHU1xJMOqfRsVfPJ

That's a very nice manual!  Anyone learning to do maintenance on a trials bike (regardless of brand) would be well-advised to study it. 

Unfortunately, there is almost no content about the gearbox (see page 49).

[mcman56]

I was curious so looked at the manual.  It looks like the minimum piston clearance for the 250 is 0.050 and the maximum is 0.080.  What is the 0.100 "Assembly" number?

 

 

 

 

[konrad]

At first, I was going to say the "assembly" number is the service limit.  But viewing that table in the context of the other displacements, it makes no sense at all.  It's a horrible table!

[SamAs]

On 9/8/2025 at 11:59 AM, konrad said:

That's a very nice manual!  Anyone learning to do maintenance on a trials bike (regardless of brand) would be well-advised to study it. 

Unfortunately, there is almost no content about the gearbox (see page 49).

Hi, sorry about the jumping between posts I’ll try keep it on this one now, I’ve uploaded a video to YouTube in case you or anybody with either a similar issue or similar experience can listen to. Thanks in advance to anyone who gives it a listen and helps and hopefully this helps you too if you’re here for answers 🙂

hopefully it works. I should mention I’ve been told the clicking is a worn chain or sprockets so replacing the lot. 

Edited 4 hours ago by SamAs
Just the part about the chain at end