2002 BLASTER YFS200 WON'T START

dschulte

New Member
Aug 20, 2024
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Hello all,
I need help. I bought my 2002 blaster in March, 2024 and it ran great for 4 months with no issues. Then, the spark plug fouled. Changed it and it ran fine again. A week later, I was riding and it bogged down and died while descending a small hill. I assumed it was the plug again but it was clean and the gap was good. Long story short, I towed it out of the desert and began troubleshooting. I have replaced the ignition coil, spark plug wire/cap/plug, and the CDI unit. I have cleaned the carb a few times, torn it down to cylinder, cleaned the piston, reed valve, cylinder, etc. All the tolerances are within range as far as clearance, reed flex, etc. It does still have the TORS unit but, when troubleshooting with a multimeter, continuity readings meet specifications listed in the user manual. I have fuel to the carburetor, compression, spark, the fuel is clean, no clogged fuel lines, the air filter is clean, and I still cannot get the damn thing to fire.
I have read countless articles on this site about similar issues and it sounds like I may have a sheared woodruff key on the stator. Would this cause it to not fire? It seems like the timing is off and the service manual says the ignition timing is "adjustment free". I also read an article where the Yamaha dealership had to rewind the stator. Is that a thing? I am mechanically inclined and pretty savvy with troubleshooting, plus I'm too damn stubborn to know when to give up. Any advice is greatly appreciated!
Thanks in advance.
 
Yes a sheared flywheel key and subsequent shifting of the flywheel on the crank will cause ignition timing to be incorrect and can cause it to run poorly or not start at all. The flywheel key indexes the flywheel correctly on the crank for proper ignition timing.

When you had the top end of, how did the reedvalve look, particularly the reed petals? Worn, chipped, broken reed petals will cause poor running and difficult/impossible starting.