hurracane

just read your post was going to suggest 2 causes for the sudden loss of power/ misfiring firstly have you checked the compression as the rings may be worn and also have you checked the seal between the the exhaust and down pipe as these are faults i have found with my own tw 125 and these symptoms were the same i would say it was also a pain to start but thats just a common tw thing

is there any easy way to cure the poor spark problem on a tw125 as i have replaced the plug/cap/coil/stator/battery carbs setup and cleaned fine new air filter /oil/oil filter/fresh petrol it will sometimes bump start and will rev properly so i dont think its a compression problem checked valve clearances and timing im just running out of ideas i know the spark has never been great but it seems 4 years of use has finally killed the bike

ive had this problem before im guessing you were buying a pattern part you will find that its more of a universal front sprocket as it fits 30 odd bikes mostly chinese copies if you buy a oem part you shouldnt have this problem i bought various ones off ebay and all had the same problem you can also order a locking plate from your local yamaha dealer i have learnt from previous mistakes and for the couple of quid it costs to replace these parts ie locking plates sump plugs etc its easier to have a spare to hand when you do the job just incase the original breaks

yes there is AKRAPOVIC RACING SP SERIES (OPEN) EXHAUST SYSTEM for the YAMAHA TW 125 (1999-2004) they do a complete system but its not road legal they also do a slip on the system costs about £461 and the slipon is £360