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Discussion Starter · #1 ·
Got a 2014 trx450er won’t start mind you started before mods, did piston rings, carb slid and mild port polish I rebuild this thing a million times never had a problem now I’m stumped, it’s got compression spark and fuel the timing is dead nuts on I check it probably 10 times tore it down to make sure rings were right and they are, had someone double check timing he said it’s perfect also valves are dead on 12 exhaust 6 intake I had to pull the carb and do the slide could I have messed up the throttle position sensor I unplugged it but still no start back fires every 20 times it’s turned over. Any ideas I’m defeated right now got countless hours into a wheeler that don’t run
 

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Making HP ain’t free. . .
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I 100% am not trying to sound like a prick, but if you KNOW it has compression, spark, and fuel, and you KNOW your valve clearances are right, and you KNOW that your timing is dead on, it should start. Something in that chain of events is not correct, so you need to go back through and figure out what it is. Have you verified compression with a gauge? Have you pulled the plug and verified by sight that it’s sparking? Do you smell gas when you’re cranking it? Why did you replace the rings and not the piston?
 

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Got a 2014 trx450er won’t start mind you started before mods, did piston rings, carb slid and mild port polish I rebuild this thing a million times never had a problem now I’m stumped, it’s got compression spark and fuel the timing is dead nuts on I check it probably 10 times tore it down to make sure rings were right and they are, had someone double check timing he said it’s perfect also valves are dead on 12 exhaust 6 intake I had to pull the carb and do the slide could I have messed up the throttle position sensor I unplugged it but still no start back fires every 20 times it’s turned over. Any ideas I’m defeated right now got countless hours into a wheeler that don’t run
I'm not a pro but sounds like timing is off. When im 180 out on my drag truck it does about the same. Dumps fuel until it fills the cylinder and there is enough left over after a few exhaust strokes that the spark finally catches it ignites and backfires and dies. I would start there. jmo
 

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Discussion Starter · #5 ·
I thought it was 180 out but I spun the cam 180 and valves hit the piston I thought same thing I know there’s spark because I had it in my hand and turned it over and trust me there’s spark and checked it after that on frame i did a compression test I got about 61 psi. I replace the rings twice then replace piston. No need when the piston looks new you know just new rings to freshen up. I was thinking fuel but starter fluid dosnt even make it almost start. After taking the exhaust out I put my had on it and it’s sucking and blowing threw the hole, would bad valve seating cause this, I also saw a few complaints of cam spinning idk how that would of happened off the wheeler but I got a stage one I’ll match it up and see on Monday.
 

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Discussion Starter · #6 ·
Still nothing been to a local shop and been to a buddy that knows a little about them still got nothing at this point it doesn't back fire I pulled the plug when I got home just to double check spark and it looks good and blue I checked timing against just to make sure he put it back correctly and looks spot on, got 75psi compression with 8% leak down with new piston the shop said it needed, put a new ecm in my buddy thought it was because of corrosion found. Anyone ever run into a weird issue they found?
 
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