HEADS UP!!!

Site upgrade in progress... Core site functions are working, but some non-critical features/functions will be temporarily unavailable while we work to restore them over the next couple of weeks.

Please post any bugs you encounter, but before you do, check to see if it's already listed.

Thanks for your patience while we work to improve the community.

Sign in to follow this  
Followers 0
Bradford690

My 2011 yz450f

11 posts in this topic

I would wonder about fuel pump and filters. I have never messed with an FI bike though. I just stick to the basics first, fuel, air, compression and spark.

Share this post


Link to post
Share on other sites

pump it a few times quickly to get the stator going, then give it a hard one. Also mine always starts much easier with 1/4 throttle... now with the gytr piston and cams its another story :(

Share this post


Link to post
Share on other sites

On my 11' I get on it, pull the starter/idle knob out, and kick it twice very slowly. Then I kick it slowly until I find the sweet spot with the most resistance (TDC) and kick it hard and hold it at the bottom of the arc. It starts 9 times out of 10. If not, I just find TDC again and it always starts second kick. When hot, same thing minus pulling the knob out. If thats not working for you, try turning your idle up a click or two on that knob (clockwise if I remember right) and that should help. If all else fails, like someone else mentioned, check your valve clearances. My bike was getting harder and harder to start this summer and the cause was two tight intake valves. Hope that helps!

Share this post


Link to post
Share on other sites

Then I kick it slowly until I find the sweet spot with the most resistance (TDC)

 

So we're clear on it, that IS NOT TDC.  The "hard spot" is the point where the exhaust valve is allowed to close by the auto decompression system and the COMPRESSION stroke begins.  That takes place roughly 25 degrees BEFORE TDC.  In an engine without auto decomp, compression at cranking speeds begins as soon as the intake closes, about 120 degrees before TDC. 

 

TDC is "Top Dead Center", where the piston is all the way up as far as it will go.  You can feel it go past TDC by pushing against compression until you feel the engine pop forward to a second hard spot.  That's where it rolls over the top and you're trying to force it down the bore against a vacuum with all the valves closed. On the compression stroke, TDC happens after the spark, so if you kicked it from there, the engine would have to make two full turns before it had a chance to fire.

Share this post


Link to post
Share on other sites

So..... Yeah, kickstart it.. 25 degrees before TDC then. I shouldn't have thrown out TDC, I just know where the sweet spot is on my bike by feeling, I said TDC because the last magazine review on the 10'-11' 450's mentioned it being impossible to start unless you find TDC first. I assumed that since my bike starts first/second kick every time at my sweet spot it must be TDC, bad assumption apparently /:

 

Thanks for schooling me up!

Share this post


Link to post
Share on other sites

It's an extremely common and deeply ingrained misnomer to call "the hard spot" TDC.  Probably most guys do that, but it's nevertheless incorrect, and causes confusion. 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0