Hi. I recently experienced a problem while checking the V belt condition on my 2020 Aerox 155 @ 20,000 Km. Back story.... I am in Thailand (yearly 3 month break from the UK) and have had the scooter worked on twice in the problem area. 4 years ago i asked an independant to install lighter rollers, new spring and a new fixed sheave from TDA. These lasted 3 months before needing to be removed due to an awful noise/vibration. I took the original parts to the yamaha dealer where i purchased the scooter for them to put it back to original. Unfortunately, here in South East Asia, torque wrenches are not used much and air driven wrenches are prefered. So, when i came to undo the front pulley nut, within a couple of nut rotations it slackend up and spat swarf out of the back of the nut, my heart sank ! I could not even run the nut off as it would not catch on the shaft thread. I was hoping that it was just the nut that had lost its thread, so i ordered a new M12x1.25 nut and some nut splitters but did not have the access to get onto the nut square to use the splitter. All that was left to do was to use a fine cutting disc in a 4 1/2" angle grinder on the nut. As can be seen, the new uprated nut is nearly twice the size and this leads me to believe that there have been enough problems reported from Yamaha service departments to warrent the uprated part. I'm guessing that my issue of the shaft being stripped of its thread is down to being over torqued with air driven wrenches by one or both of the garages that torqued the nut for me. So, with a damaged shaft thread i priced the parts up, new crank, seals etc and 4 hours labour to remove the engine, split engine and replace the crank, i was looking at around £350 GBP. I shudder to think how much this cost in the US or Europe. I decided to give cutting a M10x1.25 thread on the shaft a go, assembled a 1" die holder, cutting oil, vernier and a split M10 die, needed to be a split die rather than a button die as the hard stainless shaft would need multiple cuts (split die can be opened up to to make shallower cuts). As i had never cut a thread before i watched vids on the tube which explained the process. The M12 shaft needed to be reduced to exactly 10mm to cut an M10 thread, this was pretty easy as when the belt and sheaves are removed, putting the bike on centre stand and running at idle, the shaft spins as if the part was in a lathe. I used a fine file on the spinning shaft to remove all traces of old thread all the way down to fixed sheave splines and finished it off with some emery cloth for a smooth finish. The vids i watched suggested a 45 degree chamfer to get the die started, i tried three times without success so increased the chamfer to around 60 degrees and this got me started. Plenty of cutting oil and one turn forward, half a turn back to clear the swarf worked for me. The shaft needs to be kept immobile, i did this by reversing the fixed sheave onto its splines and locking it off with large screwdriver as in the picture. I reassembled everything, leaving the smaller washer off the shaft, gave the new M10 nut a nip up with threadlock applied, marked up all the parts so i could see if anything moved whilst testing and i'm happy to say that at the moment there are no issues so far, it is being ridden 30Km to work and 30 Km back every day by my girlfriend. Long term reliability is still to be seen. I wrote this to hopefully help someone who finds themselves in a similar situation who is looking at a large repair bill they can not afford. Thailand 2019 Honda click 125 2020 Aerox 155 Ltd 2023 xmax 300 TechMax UK ADV 350