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2007 trx450er
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Discussion Starter · #1 ·
This is my first post here. Just acquired a 2007 trx450er. I put a new wiseco oem spec piston and rings in it to start. ( got it non running). Used the manual. Valves to spec, timing on. Checked everything more than once. It is bone stock. Stock exhaust. Uni filter. Air box lid on. Also rebuilt the carb with new seals, jets. It has a “scary fast power shot” accelerator pump cap. New accelerator pump internals. Have a 162 main ( same size that was in there when i got it) 75 small and 42 mid. Air fuel mix out 2 1/4 turns. Needle is on 3rd setting from bottom. The bike starts no problem when its COLD. But back fires occasionaly, hard to get to hold a idle no matter what i do with idle and fuel screw. Once it is hot and shuts off. Won’t start again until it is cold just cranks away wont fire. Let it cool to the touch, it will start again and repeat the process. This is my first 450 and atv at all in years im a harley guy. Have been reading a lot. I know its a no no to use throttle to start but seems to be only way it will. Also when it is hot and not starting. The starter sounds weaker. I’ve read a lot on here, think it may be decomp possibly? I set it with a feeler gauge didnt have compressor gauge waiting on one now. Any other ideas what it could be? It also seems to get hot pretty fast. Any help or input is appreciated.
 

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2014 trx450er
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14 Posts
When my quad did the hot no start, it was my valves. I have the auto de-comp valve, haven't had to deal with the decomp valve. I had to replace them, due to them being stretched. I put kibble whites in, never had a problem after that. Don't know how much shim height you got left so you might just need to re-shim if its the valves. Also don't know how old your battery is but more recently, I had a weak battery, got a new one and been good so far. Check battery connections for corrosion as well, shit happens.
 

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2007 trx450er
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3 Posts
Discussion Starter · #3 ·
When my quad did the hot no start, it was my valves. I have the auto de-comp valve, haven't had to deal with the decomp valve. I had to replace them, due to them being stretched. I put kibble whites in, never had a problem after that. Don't know how much shim height you got left so you might just need to re-shim if its the valves. Also don't know how old your battery is but more recently, I had a weak battery, got a new one and been good so far. Check battery connections for corrosion as well, shit happens.
Yea i checked valves, all in spec is why i am leaning towards decomp. I have read guys having decomp in spec with feeler gauge but then when checking compression being way off and having to adjust… battery is also brand new.. if decomp adjustment with compression gauge is correct i am going to direct my attention back to valves i guess. Thanks
 

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2007 trx450er
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3 Posts
Discussion Starter · #4 ·
When my quad did the hot no start, it was my valves. I have the auto de-comp valve, haven't had to deal with the decomp valve. I had to replace them, due to them being stretched. I put kibble whites in, never had a problem after that. Don't know how much shim height you got left so you might just need to re-shim if its the valves. Also don't know how old your battery is but more recently, I had a weak battery, got a new one and been good so far. Check battery connections for corrosion as well, shit happens.
Just checking back.. so i set the decomp adjustment using a compression gauge instead of going off the books feeler gauge measurement. Cranked with throttle wide open a few times until it held a steady psi. To the books feeler gauge setting it was only around 23 psi. Adjusted decomp arm until it held at 55 psi on compression gauge. Problem solved. Haven’t had a issue since.
 

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When my quad did the hot no start, it was my valves. I have the auto de-comp valve, haven't had to deal with the decomp valve. I had to replace them, due to them being stretched. I put kibble whites in, never had a problem after that. Don't know how much shim height you got left so you might just need to re-shim if its the valves. Also don't know how old your battery is but more recently, I had a weak battery, got a new one and been good so far. Check battery connections for corrosion as well, shit happens.
That's so nice!
The enthusiasm and the passion is on another level.
 
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