Bike that won't start.



26 replies to this topic
  • Spilly

Posted August 13, 2016 - 01:18 PM

#1

I'm pretty new to the small engine thing. And I've never dealt with carburetors. But I got my hands on a bike that won't start and I'm seeking help to trouble shooting what the issue is from someone who knows more then me.

 

My bike is an 07 YZ450F.

 

I know the motor rotates easily, motor is good, I have spark, I have gas flow, air filter was cleaned, I cleaned the carb, fresh gas and new oil and coolant. New plug today. How would I go about adjusting the carb on a bike that won't start, or how would I diagnose if the carb is being a dink at all?

 

 



  • Ninjaman1

Posted August 13, 2016 - 01:20 PM

#2

Have you checked compression?
Did it run previously or hasn't ran since you got it??

  • Ninjaman1

Posted August 13, 2016 - 01:23 PM

#3

Sometimes an easily rotating motor is a bad sign, should have tons of compression. Is decompression switch stuck open? There are many things to check and compression should be first

  • Spilly

Posted August 13, 2016 - 01:45 PM

#4

Sometimes an easily rotating motor is a bad sign, should have tons of compression. Is decompression switch stuck open? There are many things to check and compression should be first

I had the plug out, I changed the timing chain and when I had the valves all closed I was rotating the flywheel with my hands. I don't have a compression tester for the smaller engines mine only fits a normal sized spark plug but I will get it tested soon, the piston and valves looked brand new, the valve gaps were all spot on aswell. And is the decompression switch the little lever on top of the clutch lever?

 

 

Have you checked compression?
Did it run previously or hasn't ran since you got it??

 

Not yet. I know it has compression from trying to kick it and even rotating in with the plug in. but I don't know the psi's yet so I can't say its good but i believe its probably in range. and Yes I did get the bike running when I first seen it, didn't run awesome but it idled with like 6 year old gas in it. I didn't want to work it too much till i got it looked over well.



  • Ninjaman1

Posted August 13, 2016 - 04:38 PM

#5

Has timing been properly set? Didn't run after the timing chain swap??

  • Spilly

Posted August 13, 2016 - 05:21 PM

#6

Yeah I believe I got it timed right. Had the mark on the flywheel lined up with the mark on the stator cover and the cams were set properly.

  • Spilly

Posted August 13, 2016 - 05:24 PM

#7

Here's a pic
Or maybe not lol. My phone doesn't want to upload a pic.

Attached Thumbnails

  • image.jpeg

Edited by Spilly, August 13, 2016 - 05:28 PM.


  • Ninjaman1

Posted August 13, 2016 - 05:33 PM

#8

Would need to see crank mark to be sure it was set right
And the front gear looks like it's off one tooth to me in pic

  • Krannie McKranface

Posted August 13, 2016 - 08:30 PM

#9

Set the fuel screw at 1.5 turns.

Raise the idle / turn the screw in a 1/2 or more turns

Clear the cylinder; 10 kicks with the throttle wide open and the kill button on

Fresh fuel



  • Spilly

Posted August 14, 2016 - 03:33 AM

#10

Set the fuel screw at 1.5 turns.

Raise the idle / turn the screw in a 1/2 or more turns

Clear the cylinder; 10 kicks with the throttle wide open and the kill button on

Fresh fuel

Ok, I'll give it a go. Thank you


Would need to see crank mark to be sure it was set right
And the front gear looks like it's off one tooth to me in pic

I'll add it for you



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

Posted August 14, 2016 - 03:35 AM

#11

Flywheel

 

The camera was off to the side a bit, it looks a bit off but it was right on. I had the light in one hand and phone in the other.

Attached Thumbnails

  • image.jpeg

Edited by Spilly, August 14, 2016 - 05:48 AM.


  • mcmaxx

Posted August 14, 2016 - 06:53 AM

#12

The lever on the clutch perch is not a decompression lever, it is a hot start lever, don't use this when trying to start a cold engine, it won't hurt anything just make it harder to start. There are many videos about starting a yz450 that are very helpful. I have a 07 yz450 my starting procedure is this, cold engine- turn gas on- pull chock out-give two to four full twists of the throttle-move engine to top of compression and kick. has yet to fail me on both 07 450s that I have owned. 



  • grayracer513

Posted August 15, 2016 - 06:32 AM

#13

...is the decompression switch the little lever on top of the clutch lever?

 

 

No, it's automatic, internal, and it's not a switch. And it won't "stick open", either. 



  • Spilly

Posted August 15, 2016 - 08:48 AM

#14

Alright did everything everyone said and I can get it to back fire now. Still won't fire up but there is combustion

  • Spilly

Posted August 15, 2016 - 10:27 AM

#15

I'm going to go look over it again, make sure my timing is on and stuff.



  • dougla12

Posted August 15, 2016 - 10:53 AM

#16

Maybe start with pulling the carb and just cleaning it out .

I know a lot of people wouldn't recommend this. But sometimes what I do is hold the throttle open and just spray 1 squeeze of gas in. (make sure it's the mist and not stream). Then close throttle and kick.The engine should start and run for a second or two

Edited by dougla12, August 15, 2016 - 10:54 AM.


  • xtremeoffroadllc

Posted August 15, 2016 - 11:00 AM

#17

Here's a pic
Or maybe not lol. My phone doesn't want to upload a pic.

 

 

Cams are correct. Just be sure you are on the right mark on the flywheel.   Some of the yamahas have the following mark >>    "   I  "      "  I     I  "       " I---I  I "  

 

always use the last mark, or if there is a T.  NOT F



  • xtremeoffroadllc

Posted August 15, 2016 - 11:01 AM

#18

What elevation are you at? What are your mods?

 

Im going to tell you how to check everything. I need to know as much as possible about this bike. 



  • xtremeoffroadllc

Posted August 15, 2016 - 11:03 AM

#19

PM me if youd like



  • Spilly

Posted August 15, 2016 - 11:23 AM

#20

PM me if youd like

Perfect! Bikes a 2007 YZ450F

 

Fuel Screw = 1 1/4 turns

Main = AB165

Pilot = 42? (paper has oil on it and can't complete read the number, looks like 42 but can't see the 4 real good)

Needle = 5 (I moved the needle from 4 to 5 when cleaning via some advice I got on how it was stuttering in the mid range)

 

My elevation is under 500ft, aroung 350-450.







Related Content

Forums
Photo

The "going back to the other darkside" adventure... by Monk


Dirt Bike   Make / Model Specific   KTM   250/350/450/505 SX-F & XC-F (4-Strokes)
  • Hot  94 replies
Forums
Photo

yz250x vs 450 4t comparisons (preferably desert riding) needed by JakeNorthrupYZ450F


Dirt Bike   Make / Model Specific   Yamaha   Yamaha 2-Stroke
  • 9 replies
Forums
Photo

Snake pit oct 30th by The Anvil


Dirt Bike   Dirt Bike Regional Discussion   California
  • Hot  293 replies
Forums
Photo

YZ450F 03 Sparks driving me crazy by SirAttard


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

2016 YZ450 by CaptainKnobby


Dirt Bike   Dirt Bike Technical Forums   Suspension
  • Hot  59 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.