07 450 No Power

Yamaha YZ450F 2007

14 replies to this topic
  • Mxdude91

Posted March 23, 2014 - 05:14 PM

#1

Rebuilt the top end 15 hrs ago and recently checked valve clearances(piston and rings,valve seals,cam chain,gaskets,valve adjustment)Runs great been changing oil/filter every 3 rides. I just adjusted the clutch cable and replaced the air filter,changed oil(did not ride it yet since doing this)


Here is what i belive caused my issue,I started it first kick starts right up wtih the choke on and then pretty much hit the rev limter and cut it right back off.I regret doing that.i know it was not wise but who hasnt done something stupid while drinking.

So i go to ride it the next day and it has absolutely no power,no wierd noises,bike sounds the same when you give it gas but doesnt really effect my speed

I pulled the engine out and "inspected" engine timing,valve clearance,spark plug,top of the piston but not the rings,valve springs,valve seals,valves dont look bent,engine oil was good and filter clean(everything is looking okay).

Im looking for some advise at what to look at next?Any help is greatly appriciated thanks

Edited by Mxdude91, March 24, 2014 - 09:26 AM.


  • Mxdude91

Posted March 25, 2014 - 03:29 AM

#2

Update,compression check and I only have 90 psi.

  • grayracer513

Posted March 25, 2014 - 06:53 AM

#3

Bear in mind that compression testing on any high compression single cylinder is fairly inaccurate anyway, since many of them can barely even be kicked over at full compression, but it's an almost completely pointless exercise when you have auto decompression.  "Somewhere around" 90 psi is about what I'd expect.

 

Double check your cam timing one more time.  I can't think of anything else of the top of my head that would have related directly to revving it hard and chopping it.  If the cam timing really is OK, then ignore the fact that the "stupidity" ever happened and troubleshoot it as if you've never seen the bike before.



  • Mxdude91

Posted March 25, 2014 - 09:20 AM

#4

Ive checked timing.its spot on,How would I check the auto decompression to see if its working as it should and could a carb cause a issue like this?because I had just changed the air filter possible for particles to fall into intake...thanks a lot for your opinion on the compression test,I'm use to doing compression test on car/trucks.and I do agree that I may of feared the worst and jumped to conclusions on the engine...

  • grayracer513

Posted March 25, 2014 - 09:38 AM

#5

Even with 4 or more cylinders and an electric starter, conventional compression testing is more useful in finding significant variations between cylinders than on absolute numbers, unless of course the readings are way off the normal range.

 

The auto decomp mechanism is virtually too simple to fail, and is normally only affected in any way that really shows up by the cam timing being off.  You can operate it by hand, and watch it work as you turn the engine.  Read: http://www.thumperta...e/#entry5732518



  • Mxdude91

Posted March 25, 2014 - 12:40 PM

#6

I do not believe my engine is to blame after I was able to get a hold of a cylinder leak down tester.

Attached Thumbnails

  • 1395779945302.jpg


  • Mxdude91

Posted March 25, 2014 - 01:02 PM

#7

It just hit me the Clutch cable is to tight is my guess IMA put the bike back together.

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

Posted March 26, 2014 - 09:47 PM

#8

are you still drinking?   :naughty:



  • Mxdude91

Posted March 27, 2014 - 12:41 AM

#9

Haha,yeah Im feeling a lil stupid...but when my bike stopped running right after a cold hard rev I instantly jumped to conclusions...and had forgotten about how I had adjusted the clutch cable after riding last time..so after checking everything I could imagine it came to me.the engine could be running fine but if the power of the engine was sorta getting to the transmission it would cause this issue.thanks gray racer for your help it really saved the day because I thought 90 psi was low for a compression test.I rode yesterday evening and man was it good to be back on the trails

  • grayracer513

Posted March 27, 2014 - 08:25 AM

#10

I find it interesting how the problem of a slipping clutch was expressed as a lack of engine power.  That threw the entire diagnosis completely off the mark.



  • Mxdude91

Posted March 27, 2014 - 09:22 AM

#11

The bike would move it just didn't have the torque it had before..I would say thats a lack of power

  • grayracer513

Posted March 27, 2014 - 10:45 AM

#12

If you had a bald tire on wet concrete, you'd have exactly the same condition, but it would be inaccurate to say that it was a lack of power.  Problems need to be accurately understood and described in order to be correctly diagnosed.



  • Mxdude91

Posted March 27, 2014 - 04:24 PM

#13

Thanks for your help grey,sorry I felt like the bike had no power,I described it to the best of my knowledge at the time I made the post and tried to keep the post up to date with where I was at with diagnosis.

  • grayracer513

Posted March 27, 2014 - 06:24 PM

#14

Thanks for your help grey,sorry I felt like the bike had no power,I described it to the best of my knowledge at the time I made the post and tried to keep the post up to date with where I was at with diagnosis.


You learn as you go. With a slipping clutch, you will hear the engine "sounding" good, but it will rev up without there being a corresponding increase in speed. That should have told you there was a problem with the stuff connecting the wheel to the engine.

If it was truly down on power, it wouldn't sound quite right, and you would not hear it revving up without the expected acceleration to go with it.

See the difference?

  • Mxdude91

Posted March 27, 2014 - 06:26 PM

#15

I follow ya





Related Content

Forums
Photo

White/Blue Smoke on throttle - 07 450fw by fldrifter


Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • Hot  43 replies
Forums
Photo

07 yz450f stall then hard to start when hot by Family Man


Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • Hot  56 replies
Reviews

Yamaha YZ450F 2007 by ThumperTalk


Yamaha YZ450F 2007
  • * * * * -
  • 35 reviews
  • Last review by Yammy Rider
  • On November 29, 2016
Forums
Photo

Pics of your 06-09 yzf 450 by tmrider


Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • Hot  268 replies
 
x

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.