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Discussion Starter · #1 ·
I just rebuilt the engine on my 2007 Honda 450er. It has a 480 big bore with a 12:1 vertex piston, HRC header with shorty big gun silencer, HRC cam, and K&N air filter. It sounds like it wants to start but it won’t. I’m 99% sure my valve lash and timing is set right. I’m usually pretty good at diagnosing issues on motors but this one has me stumped.

Any help would be appreciated.
 

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Making HP ain’t free. . .
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IFR8H11 is the plug, and premium gas is recommended, but gas octane won’t cause it to not start. Generally a No start condition after a rebuild is because of timing being off. I would pop the valve cover off and take a second close look. Get down on your knees and make sure your timing mark is lined up and the cam gear marks are level with the head as well. Have you pulled the plug and checked to see if it’s sparking while turning it over? can You smell gas coming out the exhaust?
 

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Discussion Starter · #5 ·
IFR8H11 is the plug, and premium gas is recommended, but gas octane won’t cause it to not start. Generally a No start condition after a rebuild is because of timing being off. I would pop the valve cover off and take a second close look. Get down on your knees and make sure your timing mark is lined up and the cam gear marks are level with the head as well. Have you pulled the plug and checked to see if it’s sparking while turning it over? can You smell gas coming out the exhaust?
Thanks for the help. It does have spark and I can smell gas fumes coming out of the exhaust and I can see that it is getting fuel because the spark plug is wet when I take it out. I will double check the timing, and get some premium gas and a IFR8H11 spark plug tomorrow. 3 more questions. While I’m in there what psi should I set the decompression mechanism at? Would jetting not being set for the big bore cylinder and piston stop it from starting? I dont think I have any head gasket issues but, would coolant getting past the head gasket stop it from starting?

Once again thanks for the help.
 

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Making HP ain’t free. . .
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Compression should be around 65 psi. Personally I only set my decompressor by clearance, not psi, and i can kick start it sitting down. Your jetting should not affect it not starting. And a bad head gasket usually won’t cause it to not start either, it would have to be extremely bad for coolant to get into the cylinder while it’s not running.
 

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Discussion Starter · #7 ·
Compression should be around 65 psi. Personally I only set my decompressor by clearance, not psi, and i can kick start it sitting down. Your jetting should not affect it not starting. And a bad head gasket usually won’t cause it to not start either, it would have to be extremely bad for coolant to get into the cylinder while it’s not running.
I will try setting my decompression to 65psi I currently have it set at 75psi.

Thanks for the help
 

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Discussion Starter · #8 ·
Compression should be around 65 psi. Personally I only set my decompressor by clearance, not psi, and i can kick start it sitting down. Your jetting should not affect it not starting. And a bad head gasket usually won’t cause it to not start either, it would have to be extremely bad for coolant to get into the cylinder while it’s not running.
What clearance do you set your decompression at? When checking decompression psi do I hold the throttle wide open or do I leave it closed?

thanks for the help so far.
 

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Discussion Starter · #10 ·
Just finished working on it for the night I put the NGK IFR8H11 spark plug in and I now I have premium gas in the tank. The timing ended up being off by a tooth and it almost starts if I take the air filter off when trying to start it it will almost start and if I put the air filter back on it doesn’t sound like it wants to start so I think I will try a richer jetting tomorrow and see if it starts. I am currently using the jetting for the HRC kit. Do I sound like I am on the right track? Sorry if I ask a lot of questions. I really appreciate the help so far.
 

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I set the decompressor at .017”. When checking compression yes you hold throttle open. But like I said, I’ve never set my decompressor by psi and my machines start after two kicks even if sitting for months. Are you getting a good spark?
 

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Discussion Starter · #12 ·
I set the decompressor at .017”. When checking compression yes you hold throttle open. But like I said, I’ve never set my decompressor by psi and my machines start after two kicks even if sitting for months. Are you getting a good spark?
I have bright blue spark coming from the spark plug. I will set my decompressor clearance to .017”

Thanks for the help.
 
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