Yz400f starting issues please help

So I replaced the spark plug because it want starting. The plug was fouled because after I replaced it started. Cleaned the carb and I think the float might be stuck cause it leaks gas out the carb would that cause it not to start? Or could it be the coil I just need help any feed back helps.

clean carb and spark plug and try again, those things will not start if flooded.Used to have one,miss it quite abit

Leaking gas out the carb could be caused by an incorrect float level or stuck float, a damaged needle valve/seat, or a leaking bowl drain screw (if you have a drain screw).  Yes it's a problem but I don't think this would cause a no-start condition, unless the fuel level was so high that it runs into the cylinder.  I guess this is possible since the tank is above the engine providing enough flow/pressure to flood everything.


Remove your carburetor and check the needle valve condition, the drain screw condition, and the float level.  It's not terribly hard, just be careful and take your time especially while checking the float level, this is a precise measurement.


One more thing: If your carburetor is the factory/stock unit, those are known to be problematic, they were not sorted out very well.  I have a 1999 YZ400F and I know.  My mechanic and I tried many times to get the stock unit working properly, and we eventually decided to replace it with a used unit from a 2005 CR450F ($100 on Ebay), re-jetted of course.  *Most* of the 4-stroke carb'd bikes use similar models of carburetor, we just had to check the overall length of the carb and the barrel diameters.  Good luck.

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