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Discussion Starter · #1 ·
I have a 09 Yfz450R. It has a 13.5:1 piston, +1mm intake valves, intake cam, 3mm bored throttle body and vortex ignition. It has run great with this setup till a race last fall. I raced two motos and it ran great, third moto wouldn't start, got it to pull start but had to stay on the gas or it would die. Been working on this thing for a month and can't figure it out, already missed first race of this year. It will start and idle fine with stock ecu but dies as soon as you rev it up. If you put a timing light on it you can see the spark is lost as soon as you rev it up. Sometimes I can get it to start with the vortex but acts the same way. If I can baby the throttle it will run but bogs bad at 3/4 throttle and will die if you let off after wot. Same performance with stock ecu,vortex or stock ecu with lexx piggy back controller. When it won't start it backfires out exhaust and intake like the timing is off. Wire harness has been tore apart and checked for shorts. Timing and valves all check out good. Verified gears haven't some how shifted on cams. Verified decompressor isn't stuck open on exhaust cam. Stator, pickup coil, coil, sparkplug, battery, tps, main relay replaced with oem yamaha parts. Tip over sensor, fuel pressure sensor, intake sensor all check out. Ground redone. Does not have oem kill switch and Pro Armor tether disconnected. Verified flywheel key wasn't broke. Fuel injector cleaned, confirmed it's pumping fuel. Tank drained, new fuel added. If anybody has any ideas I'd greatly appreciate some input. Next race only a week and a half off and I'm stumped and sick of throwing money at it! Thanks for reading-Butch
 
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