Need help with no start on Honda 450 engine

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2/25/2018 6:23 PM

Hi guys, please bear with me on this one. I know this is the vital site but I'm having no luck on the 4-wheeler forums. My brother has an '07 Fourtrax 450 ER that won't start. I was hoping there would be enough similarity between this engine and the CRF450 engine (pre-EFI) that someone might be able to help.

So, the quad hasn't run in 3 years, but it ran fine when it was parked. The fuel was drained out of the carb. The carb has been cleaned out with a blow gun, and pressing the throttle shows gas shooting up from the accelerator pump. There is spark and compression is 50 PSI (this is within spec because of auto-decompression). This is an electric-start engine, no kickstarter.

Any ideas? We did try gas in the spark plug hole but it just back-fired. I've read on the quad forums that the timing may be off but it ran when it was parked, no changes. I'm just an old 2-stroke guy so I'm at a loss with a somewhat modern 4-stroke engine with a FCR carb. Thanks!


2/25/2018 10:13 PM

Compression test is pointless. Leakdown is a better way to go. But if it ran fine when it was parked id still be leaning towards something in the carb. The accelerator pump isnt your main or pilot so just because that works doesnt mean its getting fuel. Ive seen guys clean a carb and it still be clogged. Check for cracks in the intake boot, but id pull the carb off again. Better yet buy new jets. They are cheap.


2/26/2018 1:11 AM

On your carb, make sure the accelerator pump timing is correct. The black plastic arm under the cables should have just the slighest amount of play. This will get your timing close.

The slide also has a height measurement. On my kx250f its 3.25mm on the intake side but im sure its different for your quad.

Also set your fuel screw to the stock setting. Usually 2 turns out is good.

Last thing is CLEAN the carb. Just because you blew it out doesnt mean the float valve isnt sticking in the hole. Even with no gas it can gum up.


2/26/2018 4:50 AM

Take the carb off and do a real soak cleaning as the jets are clogged. Blowing with an air gun will not clear them.

Paw Paw


2/26/2018 6:14 AM

Here is a cheap tool that may help you out as mentioned in the last post. I ordered a couple of these last week and they were just 13 bucks. You may can get it a little cheaper else where but here is a link anyways.


2/27/2018 5:10 PM

Thanks guys! gonna give all that a try this weekend