Yz400f starting issues please help

2 replies to this topic
  • yz400fsandblaster

Posted April 24, 2014 - 04:21 PM


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.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • husky300racer

Posted April 24, 2014 - 05:11 PM


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

  • DGXR

Posted April 29, 2014 - 01:55 PM


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.

Related Content

WR Camshaft Swap Info - last post by jamesm113

WR Camshaft Swap Info

  • 0 replies

BIGBORE FOR YZ450F 2006? by Taattie94

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 5 replies

Snake pit oct 30th by The Anvil

Dirt Bike   Dirt Bike Regional Discussion   California
  • Hot  293 replies

Wilson the Blue Privateer by jetfuel

Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  50 replies

Chubby dad, looking at bikes , First trip to the orange/black forum ! by Slow_ride

Dirt Bike   Make / Model Specific   KTM   250-530 EXC/MXC/SXC/XC-W/XCR-W (4-Strokes)
  • Hot  28 replies

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.